On the basis of previous studies, an antioxidant enriched high yield potential genotype (Accession VA13) was selected for this investigation. This genotype was grown in pots of a rain shelter open field of Bangabandhu Sheikh Mujibur Rahman Agricultural University, Bangladesh (AEZ-28, 24° 23′ north latitude, 90° 08′ east longitude, 8.4 m.s.l.). The seeds were sown in plastic pots (15 cm in height and 40 cm length and 30 cm width) in a randomized complete block design (RCBD) with three replications. N: P₂O₅:K₂O were applied @92:48:60 kg/ha as a split dose. First, in pot soil, @46:48:60 kg ha 1 N: P₂O₅:K₂O and second, at 7 days after sowing (DAS) @46:0:0 kg/ha N: P₂O₅:K₂O. The genotype was grouped into three sets and subjected to four salinity stress treatments that are, 100 mM NaCl, 50 mM NaCl, 25 mM NaCl, and control or no saline water (NS). Pots were well irrigated with fresh water every day up to 10 days after sowing (DAS) of seeds for proper establishment and vigorous growth of seedlings. Imposition of salinity stress treatment was started at 11 DAS and continued up to 40 DAS (edible stage). Saline water (100 mM NaCl, 50 mM NaCl and 25 mM NaCl) and fresh water were applied to respective pots once a day. At 40 DAS the leaves of Amaranthus tricolor were harvested. All the parameters were measured in six samples.

At Moderate salinity stress (MSS) and Severe salinity stress (SSS) conditions, leaf color parameters and pigments, vitamins, phenolic acids, flavonoids and antioxidant capacity of A. tricolor leaves were very high compared to control condition. Hence, salt-stressed A. tricolor leaves had a good source of natural antioxidants compared to plant grown in normal cultivation practices.

They were grown in 14 cm plastic pots containing soil mixture of peat:sand (1:1) and maintained in a controlled greenhouse conditions in a private nursery located on Alexandria-Cairo Desert Road. The soil was fertilized with 2 g l -1 Crystalon (19% N: 19% P: 19% K, Chema Industries, Egypt). The plants were maintained at natural light conditions and the temperature ranged between 15 and 28 ℃ . Plants were watered every two days with 2000 and 4000 ppm NaCl solution. The plants subjected to saline conditions (watered with 2000 and 4000 ppm NaCl solution) were treated with 7 ml/L weekly application of Seaweed extracts (SWE) (Ascophyllum nodosum, Stella Maris, Acadian Seaplants, Canada) as foliar spray until drop-off two weeks ahead of saline conditions. A foliar spray of 5-aminolevulinic acid (Sigma-Aldrich, Germany) at (3, 5 and 10 ppm) was applied weekly until drop-off to all plants during saline conditions and untreated plants were considered as controls. Experiments continued for 6 weeks in two consecutive seasons of 2016 and 2017 and the plants were distributed in three blocks and each treatment was represented by 5 replicates with a total number of 270 plants. The NaCl was added to the tank gradually and the electrical conductivity (EC) was measured using EC meter.

There were significant increases in branch length and number of branches per plant, fresh and the dry weight in Seaweed extracts (SWE) + 5-aminolevulinic acid (ALA) treated plants under saline irrigation conditions compared to control. These morphological improvements associated with several physiological changes in treated plants including increased accumulation of specific phenols (robinin, rutin, apigein, chlorogenic acid and caffeic acid) and increased antioxidant activities of leaf extracts. There were also increased the chlorophyll composition and the accumulation of sugars and proline. Improved transpiration and photosynthetic rates as well as stomatal conductance were also detected in treated plants. The expression of several genes responsible for water management, flavonoid accumulation and antioxidants accumulation was enhanced in SWE + ALA treated plants.

Under normal and saline irrigation conditions, there were changes in genes expression following SWE and ALA applications.The transcription levels of ANN1 and ANN2 increased significantly in SWE + ALA treatments compared to control under non-saline and saline conditions . However, transcription levels of MYB44 showed no significant variations among treatments. PIP1, P5CS1 and CHS relative expressions was higher in plants treated with SWE + ALA under normal and saline irrigation conditions . The transcription levels of the redox responsive genes of APX1 and GPX3 were significantly higher in SWE + ALA treated plants compared to control treatments . Increasing ALA amount from 3 to 10 ppm had no significant effects on APX1 transcription levels under non-saline conditions. In addition, the application of SWE or ALA only had no significant effects on GPX3 transcription levels under non-saline conditions.

The experiments were conducted under controlled conditions using plastic pots having lower diameter of 7.8 cm, upper diameter of 13.5 cm and 12 cm in height. The soil was collected from the top layer (0-20 cm) from the Botanical Garden of the university. Soil was air dried crushed and sieved through 2 mm filter autoclaved at 121 ℃ for 2 h. The soil was autoclaved to exclude soil pathogens and other microorganisms if any. The autoclaved soil was poured in pots and kept in the growth chamber. The pots were filled with 500 g uncontaminated soil and partially decayed compost (cow manure) (2:1) and was used as growing medium. The cow dung was added into the soil for better performance of earthworms. A subsample of the study soil before mixing with compost was analyzed for its physicochemical characteristics. The soil used for the experiment was sandy loam soil having pH 7.8 , EC (Electrical conductivity) (µS/cm) =184.25 , TDS (Total Dissolved Solids) (mg/kg) = 130 , N (Nitrogen) (mg/kg) = 103 , P (Phosphorus) (mg/kg) = 10.6 , K (Potassium) (mg/kg) = 0.343 , %OC = 0.894, Cd (mg/kg) = ND (not detected by AAS).The Cd treatment was given by using anhydrous CdCl₂ (Minimum assay: 95.0%) procured from Hi-Media laboratories. The CdCl₂ anhydrous was added to the soil to make different concentrations of Cd 0.50 mM, 0.75 mM, 1.00 mM, and 1.25 mM (i.e. 56 mg/Kg , 84 mg/Kg , 112 mg/Kg and 140 mg/Kg respectively). The various treatments given are as shown below:(1)C0 (Control): (Cadmium absence);(2)C1: (0.5 mM Cd);(3)C2: (0.75 mM Cd);(4)C3: (1.00 mM Cd);(5)C4: (1.25 mM Cd).Each Cd treatment was given in soils without as well as with earthworms (WTE = without, WE = with earthworms). Earthworms (3 earthworms per pot) were inoculated after seven days of Cd treatment and incubated for 7 d in soil with earthworms. The seeds after surface sterilization were sown in soil containing different concentration of Cd and earthworms in plastic pots. These pots were kept in seed germinator under controlled conditions i.e. 25 ℃ temperature and 16:8 h dark: light photoperiod (1700 lx) for 15 d. Seedlings were harvested after 15 d followed by washing with distilled water. The growth and biochemical analysis was done on these seedlings.

Increased Cd uptake in plants in presence of earthworms enhances the total antioxidative capacity, metal chelating compounds and content of other antioxidants in plants grown under metal polluted soils. Earthworms can improve plant growth by improving nutrient availability to plants through their vermicasting activity. Their role in modifying soil pH and increasing metal phytoavailability made their use ideal in phytoremediation of polluted soils. Increased uptake and accumulation of Cd in plants activates the antioxidative system of plants takes place by addition of earthworms to soil.

The gene expression for the key enzymes involved in organic acid metabolism was studied to understand the role of earthworms in organic acid metabolism in plants under Cd metal stress. It was observed that in comparison to control (C0) seedlings the expression of CS, SUCLG1, SDH and FH was enhanced 1.72, 1.58, 1.65 and 1.88 folds in seedlings given C4 treatment with 1.25 mM dose of Cd respectively . However, after supplementation of earthworms to Cd treated soils given C4 treatment resulted in further enhancement in expression of CS (2.53 fold), SUCLG1 (2.35 fold), SDH (2.13 fold) and FH (3.06 fold) .

Seeds of B. juncea (cv. RLC-1) were given pre-sowing treatment with 24-epibrassinolide (EBR) solutions (0 and 100 nM EBR/L) for 8 h. Petri-plates were lined with Whatman1 filter paper and were supplemented with different imidacloprid (IMI) concentrations (0, 150, 200, and 250 mg IMI/L). The EBR treated seeds were rinsed with distilled water and grown in Petri-plates supplemented with IMI solutions (three petri-plates for each treatment). The Petri-plates were kept in seed germinator (temperature = 25 ℃ , photoperiod = 16 h, light intensity = 175 µmol m ^-2 s^-1) and the seedlings were harvested 10 days after sowing for further analysis.

Seed soaking with 24-epibrassinolide recovers the impaired growth of B. juncea seedlings under imidacloprid stress by modulating the expression of genes encoding key enzymes including chlorophyllase, citrate synthase, succinyl Co-A ligase, succinate dehydrogenase, fumarate hydratase, malate synthase, phytoene synthase, chalcone synthase, and phenylalanine ammonialyase.

In the present study, as compared to control seedlings, the expression of gene CHLASE (encoding chlorophyllase) was observed to increase by 2.66-fold under IMI toxicity, but seed soaking with EBR significantly reduced the expression of CHLASE to 1.07-fold in the seedlings under IMI toxicity . Data analysis using two-way ANOVA and Tukey's HSD showed significant difference for CHLASE expression in B. juncea seedlings (FIMI p < 0.01, FEBR p < 0.01, FIMI * EBR p < 0.001). MLR analysis of the fold change in CHLASE expression also revealed the increased expression of gene with IMI toxicity and EBR application (positive betaIMI-value), whereas interaction between IMI and EBR was observed to be negative .Further, in comparison to control seedlings, the expression of PSY (encoding phytoene synthase) and CHS (encoding chalcone synthase) was significantly enhanced by 5.22 and 4.54-folds respectively in the seedlings raised from EBR treated as well as untreated seeds grown under IMI stress . Significant differences in expression PSY (FIMI p < 0.001, FEBR P<0.05) and CHS (FIMI * EBR p < 0.001) were observed after analyzing the data using two-way ANOVA and Tukey's HSD. MLR analysis of fold change in gene expression also revealed the role of EBR in modulation of gene expression of PSY and CHS. Concentrations of IMI as well as EBR were regressed positively on the fold change in gene expression of PSY and CHS, thus revealing enhanced expressions of these genes under both the treatments. Moreover, interaction between IMI and EBR was positive for PSY expression, whereas negative interaction was observed for the expression of CHS .In the present study, the expression of PAL was also observed to enhance significantly by 6.68-fold in the seedlings raised from EBR treated seeds and grown under IMI stress . After analyzing the data using two-way ANOVA and Tukey's HSD, significant difference in the expression of PAL was observed (FIMI p < 0.01, FEBR p < 0.01, FIMI * EBR P<0.05). MLR analysis of the fold change in gene expression also confirmed the role of EBR in increasing the PAL gene expression under IMI pesticide stress. Positive beta-regression coefficients were observed for IMI, EBR, and IMI * EBR .The expression of genes encoding the key enzymes involved in organic acid metabolism was also studied to understand the role of EBR in organic acid metabolism under IMI pesticide stress. It was observed that as compared to control seedlings, the expression of CS (encoding citrate synthase, 2.35-fold), SUCLG1 (encoding succinyl-Co-A ligase, 1.57-fold), SDH (encoding succinate dehydrogenase, 2.01-fold), FH (encoding fumarate hydratase, 1.57-fold), and MS (encoding malate synthase, 1.91-fold) were increased in B. juncea seedlings raised from untreated seeds and grown under IMI pesticide toxicity . However, seed soaking with 100 nM EBR and germinating them under IMI toxicity resulted in further enhancement in expression of CS (2.61-fold), SUCLGD1 (4.18-fold), SDH (2.55-fold), FH (3.73-fold), and MS (4.03-fold). Data analysis using two-way ANOVA and Tukey's HSD showed significant differences in the expression of CS (FEBR p < 0.01, FIMI * EBR p < 0.01), SUCLG1 (FEBR p < 0.001, FIMI * EBR P<0.05), SDH (FEBR p < 0.01), FH (FEBR p < 0.001), and MS (FEBR p < 0.001). MLR analysis showed that gene expression in seedlings under IMI stress as well as after the EBR seed treatment was increased as indicated by positive beta-regression coefficients. Whereas, negative interactions were noticed between IMI and EBR treatments for the expression of all genes studied related to organic acid metabolism.

After acclimation, the plants were grown independently in different light treatment chambers at 20 ± 0.2 &#8451 and 65 ± 2% humidity until the harvest date (35 days after light treatment). The white fluorescent light (70 ± 5 µmol/m²/s) was maintained for 12 h, and then each of the blue, green, red, and white lights was irradiated at 70 ± 5 µmol/m²/s for 4 h using LED arrays (DR LED Networks Co., Seoul, Republic of Korea). The spectral energy distribution of four different LED arrays was measured from 300 to 800 nm with a spectroradiometer (International Light, RPS-900, U.S.). Their maximum spectral wavelengths were 463 (blue), 518 (green), and 632 nm (red); the white LEDs had a broad spectrum. Irradiance was measured using a quantum sensor (LI-COR, LI-191, Lincoln, NE, U.S.). Water was supplied daily with top irrigation and a nutrient solution (Hoagland, pH = 5.9 ± 0.2, electrical conductivity = 1.2 dS/m) every 4 days until harvest.

A quantitation and principal component analysis biplot demonstrated that luteolin-7-O-glucoside (2), luteolin-7-O-glucuronide (3), and quercetagetin-trimethyl ether (8) were the highest polyphenols yielded under green light, and dicaffeoylquinic acid isomer (4), dicaffeoylquinic acid isomer (5), naringenin (7), and apigenin-7-O-glucuronide (6) were greatest under red light. Chlorogenic acid (1) and 1,2,6-trihydroxy-7,8-dimethoxy-3-methylanthraquinone (9) were produced in similar concentrations under both light types. The white and blue light appeared inefficient for polyphenol production.

Clausena lansium (Lour.) Skeels leaves of four developmental stages, namely, (i) leaf buds, (ii) young leaves, (iii) mature leaves, and (iv) old leaves, were collected from three 13-year-old trees grown in wampee resources nursery of Institute of Fruit Tree Research, Guangdong Academy of Agricultural Sciences in Guangzhou, China.

Increase in bound flavonoids, quercetin, and cellular antioxidant activity was observed in bound and free fractions at different stages of leaf development. Predominantly, quercetin and ferulic acid contents were high in free and bound fractions of old leaves. In addition, phenolic components depicted highly significant positive association (p < 0.05) with antioxidant activity.

Seeds were treated with sulfuric acid (98%, 10 min) and then surface sterilized with 70% ethanol (v/v) for 1 min and sodium hypochlorite solution (10%, at 10 min). After sterilization, seeds were germinated on MS media (Murashige and Skoog, 1962) containing 7 g/L agar (Duchefa, Netherlands). Cultures were maintained under 16/8 h light/dark. Explants were taken from 4-week-old leaves for inoculation with bacteria strain.ATCC15834 strain of A. rhizogenes was supplied by microbial unit of the National Research Center for Genetic Engineering and Biotechnology, Tehran-Iran. Bacterial cells cultivated on LB (Luria-Bertani) culture medium (Bertani, 1952) on rotary shaker (at 26 ℃ and 180 rpm for 48 h) in the darkened state.The leaves were wounded and inoculated with bacterial suspension for 5 min and transferred to MS media containing 7 g/L agar in darkness at 25 ℃ . After 48 h treated Explants were cultured on the 1/2 MS media containing cefotaxime (500 mg/L) and indole-3-butyric acid (IBA) (2 mg/L). Hairy roots emerged at wounded sites, after 4-weeks of incubation, and then each hairy root line was isolated from explants tissue and was subcultured weekly in new media (1/2 MS hormone-free media) with appropriate antibiotic. The concentration of cefotaxime was decreased gradually and eliminated from the culture medium after 8 subcultures and axenic root cultures were obtained. Then hairy root lines were transferred to the 250 mL Erlenmeyer flasks containing 30 mL hormone- free 1/2 MS liquid medium and incubated on a rotary shaker (120 rpm) at 25 ℃ and subcultured every two week. Hairy root line, which showed sufficient growth in 1/2 MS liquid medium, was selected for further investigations.The genomic DNA was extracted from transformed hairy root lines and plant intact roots with CTAB method . Gene-specific primers from rol B were used for amplification of the 780-bp segment in PCR analysis. The primers sequences were, F:5'-ATGGATCCCAAATTGCTATTCCCCCACGA-3'and R:5'-TTAGGCTTCTTTCATTCGGTTTACTGCAGC-3'. Thirty-five PCR cycles were performed with 5 min initial denaturation at 94 ℃ , annealing steps at 60 ℃ for 80 s, extension at 72 ℃ for 90 s, and final extension step of 72 ℃ for 10 min. The amplimer were analyzed by 1% agarose gel electrophoresis.To investigate the effects of SiO₂ NPs, various concentrations (0, 25, 50, 100 and 200 mg/L) of this elicitor were added to the hairy roots culture medium (1/2 MS + 3% sucrose, pH = 5.7) at the end of log phase of growth stages (21-days-old cultures). Hairy roots were incubated with elicitor for 24 and 48 h of exposure time. Hairy roots were harvested 7 days after elicitation and dried on sterile filter paper to remove excess surface moisture and were weighed before freezing by liquid nitrogen and stored at -80℃ until used to measure growth, biochemical and phytochemical analysis.

The effect of silicon dioxide nanoparticles on production of phenolic compounds and expression rate of pal and ras genes involved in rosmarinic acid biosynthesis pathway has been investigated in D. kotschyi. SiO₂ nanoparticles, used as an abiotic elicitor in our study, has appropriate optical, electrical and catalysts properties and has many applications in various industries as well as agriculture. This study clearly suggested that, in the presence of this nanoparticle, induction, production and accumulation of valuable compounds and corresponding antioxidant activity increased in hairy roots.

According to the results, expression levels of the pal and ras genes were influenced by elicitor concentration and exposure time. The elicitation by SiO₂ NP of 100 mg/L after 48 h of exposure time dramatically increased pal expression compared to the control. Briefly, with increasing SiO₂ NP concentrations after 48 h of exposure time, the expression level of pal was also significantly induced . Similarly, ras expression was significantly raised at 48 h after treatment by increasing SiO₂ NP concentration and enhanced to the greatest extent in 50 mg/L concentration. After 24 h of exposure time, the minimum level of ras expression was observed in the 200 mg/L SiO₂ . Amplification products of real-time PCR were assessed with 1.8% agarose gel which was corresponded to the predicted size.

Lettuce plants (Lactuca sativa L. cv. Romana Lentissima a Montare 4, FOUR-BLUMEN s.r.l., Piacenza, PC, Italy) were cultivated under the greenhouse of Agronomy and Crop Sciences Research and Education Center, University of Teramo, Mosciano Sant' Angelo (42° 53′ N and 13° 55′ E, 15 m; above sea level) from June to July 2013. The greenhouse is covered with a single layer of ethylene-vinyl acetate (PATILUX) provided by P.A.T.I. S.p.A. (San Zenone degli Ezzelini, TV, Italy); it has a natural ventilation system, and it is not provided of artificial lights, fans, and heaters. The % of reduction with respect to outdoors conditions in terms of total (W m ^-2) and PAR (µmol m^-2 s^-1) radiation amounted to 7.4% and 12.6%, respectively. Moreover, the plastic film, as expected, causes a reduction of the irradiance (µmol m^-2 s^-1) by 64, 32 and 24% on average in the ultraviolet, PAR and near infrared regions, respectively. Starting from transplanting air temperature was constantly monitored with sensors connected to a data logger (EM50 Data Collection System, Decagon Devices Inc., Pullman, WA, USA) .Seeds were sown on a nursery potting soil (Huminsubstrat N3, Neuhaus, Klasmann-Deilmann, Geeste, Germany), composed of 90% peat, 10% clay; pH 6; NPK 14:16:18, 1.3 kg m^-3; conductivity 35 mS m^-1. On 18 June, uniform sized seedlings of lettuce at the 3-leaf stage were transplanted into individual plastic pots (14 × 14 cm) filled with peat-based compost (peat:vermiculite:perilte 1:1:1, v/v); the composition of the peat moss is given as follows (percentage on dry matter): organic carbon 40%, organic nitrogen 0.1%, organic matter 80%. At 8 and 10-leaf stages, a treatment with fungicide Ortiva (a.i. Azoxystrobin 23.2%, Syngenta Crop Protection S.p.A., Milano, Italy) at the dose of 0.08 mL m^-2 was applied.The experiment was arranged on a complete randomized block design. Two nutrient-deficiency conditions and two abiotic stressful conditions were imposed starting from 4 days after transplanting (DAT), i.e. no phosphorus fertilization (named 0_P), no nitrogen fertilization (0_N), limitation of the photosynthetic active radiation (PAR, range from 400 to 700 nm) (LR) and water availability constraint (WR), plus one unstressed CONTROL. Each treatment was replicated three times and each replication consisted in 49 pots (7 rows, 7 pots per row) for a total of 147 pots per treatment; to avoid edge effects, plants were daily re-randomized with the accuracy in maintaining the same sun orientation. All the plots with no-phosphorus limitation (CONTROL, 0_N, LR and WR) were fertilized with simple superphosphate at the rate of 40 kg P₂O₅ ha^-1. All the plots with no-nitrogen limitation (CONTROL, 0_P, LR and WR) were fertilized with two applications, at 4 and 7 DAT, at the total rate of 90 kg N ha^-1 with calcium nitrate (Ca(NO₃)2). In order to standardize the amount of calcium to the plants, 0_N treatment was fertilized with 156 kg ha^-1 of calcium oxide (as the commercial product Brexil Ca, Valagro S.p.a., Piazzano di Atessa, CH, Italy). At transplanting plants were fertilized with potassium chloride at the dose of 100 kg K₂O ha^-1, and KSC Mix (Timac Agro Italia, Milano, Italy) at the dose of 0.02 kg ha^-1 composed as follows: 15% water-soluble magnesium oxide (MgO); 28% water-soluble sulphurous anhydride (SO₃); 0.5% water-soluble boron (B); 0.5% water-soluble copper (Cu) chelated by EDTA; 2.5% water-soluble iron (Fe) chelated by EDTA; 2% water-soluble manganese (Mn) chelated by EDTA; 0.2% water-soluble molybdenum (Mo); 1.5% water-soluble zinc (Zn) chelated by EDTA.Shade treatments (LR) were accomplished using a shade net in order to obtain a 85% of reduction in PAR wavelengths. PAR intensity was hourly measured with a PAR Photon Flux Sensor (Decagon Devices Inc., Pullman, WA, USA), connected to a data logger (EM50 Data Collection system, Decagon Devices Inc., Pullman, WA, USA). Per cent of shading was determined by comparing the average PAR values of net with the average PAR values of the un-shaded treatments. Nets were wrapped around a rigid and removable structure placed above the vegetation so that they covered the incoming light from the top and sides to 5 cm below the bottom of the pots. To allow air circulation, light was not limited from below.Water stress (WR) was imposed by maintaining soil volumetric water content at 30% of water holding capacity (WHC) which corresponded to 0.240 and 0.072 m³ m^-3 for no-water stressed and water stressed plants, respectively. Water loss, due to evapotranspiration, was constantly monitored with soil moisture sensors installed in 5 randomly selected pots, for each replicates (EC-5, Decagon Devices, Inc., Pullman, WA, USA); the sensors were connected to a data logger - EM50 Data Collection system (Decagon Devices Inc., Pullman, WA, USA). The pots were manually re-watered with tap water (pH 7.2, EC 0.23 mS cm^-1) every day at 18:00 h.

With the exception of light reduction, the other kind of limitation negatively influenced lettuce fresh yield; nevertheless, the reduction of PAR availability induced a decrease in the content of the main investigated phenolic compounds resulting in a strong reduction of total phenolic content as well as antiradical activity. Conversely, the scarcity of N nutrition allowed to obtain the highest total polyphenols content (TPC) and TEAC (Trolox Equivalent Antioxidant Capacity), although no differences were found in terms of the main phenolic compounds. Drought seems to improve the accumulation of caffeic, caftaric and chicoric acids in the bound forms as well as TPC and antiradical activity of the same fractions, while the reduction in P fertilization did not significantly influence lettuce leaves composition in terms of phytochemicals.

Twelve cultivars of leaf-type lettuce (Lactuca sativa var. crispa) were selected for the study. This type of lettuce forms open heads with loose leaves that do not close to cover younger leaves. Six green-colored cultivars originated from Semo, a.s., Czech Republic (Dubagold, Zlatava, and Zoltan) and Bejo Zaden B.V., Netherlands (Aleppo, Biondonna, and Kiribati); six red-colored cultivars were also from Semo (Dubared, Roden, and Rosaura) and Bejo Zaden (Carmesi, Oakly, and Spectation). The experiments were performed in the spring period (April, May). Lettuce seeds were sown in plastic pots and germinated under standard laboratory conditions (ca. 21 ℃ , 12-hour photoperiod). After germination, the lettuce plants were transplanted into a growth chamber (air-conditioned box model MC1750 (Snijders Scientific, Tilburg, Netherlands) and grown under 14/10 h (day/night) photoperiod, 21/18 ℃ temperature, 60% humidity, and 250 µmol.m ^-2.s^-1 light intensity. The commercial peat substrate (Klasmann, Germany) was used (pH 6.0, nutrient content: N: 220 mg/L, P₂O₅: 110 mg/L, K₂O: 220 mg/L, Mg: 80 mg/L). Approximately at the stage of second, fully expanded, true leaf the plants were transplanted to 0.5 l pots and kept at the same conditions for seven days to recover. After recovery, the plants were transferred into one of the three experimental conditions described below. Plants were watered regularly to avoid drought stress. Considering a high level of nutrients in the substrate and a short duration of the experiments, no additional nutrition was applied to plants.The experiments were held at SAU in Nitra (48° 19′ 7″ N, 18° 4′ 55″ E, 144 m asl). To distinguish the effects of UV radiation from other environmental factors such as temperature, humidity, and light intensity, the plants were grown in three different environments: 1. direct sunlight (outdoor conditions with high UV), 2. under clear glass (outdoor conditions with low UV), and 3. greenhouse (indoor conditions with low UV).Plants grown under direct sunlight conditions were placed into a vegetation cage (a walk-in cage surrounded by the thin wire mesh from the top and side to protect the experimental plants against birds and animals) and exposed to almost unrestricted sunlight and ambient temperature and humidity. Plants were watered as needed to achieve a fully hydrated state. Temperature outdoors was monitored.Plants grown under clear glass were placed in similar environmental conditions as those cultivated under direct sunlight, but were grown in the glass shelter constructed from clear glass sheets (thickness of 8 mm). The clear glass sheets were positioned such as to eliminate UV light coming to plants from the south and above. The backside (oriented to the north) of this glass shelter was covered by the plastic-coated wire mesh not impeding the flow of air, so the temperature and other conditions were almost identical to fully open outdoor conditions. Temperature outdoors and under the glass sheets was occasionally compared using hand-held thermometers, showing only insignificant differences. The glass cover lowered the intensity of photosynthetically active radiation (PAR) by 10-15% at noon due to absorbance and reflectance of radiation by the glass. The overhang of the glass shelter, wire mesh from the north part as well as composition of buildings from the north west and east direction was very favorable to prevent excessive access of diffuse UV radiation. Thus, despite UV radiation is not fully eliminated, its level represents only a small fraction compared to the direct UV radiation incident to plants exposed to direct sunlight outdoors.Plants grown indoors were placed in a regular greenhouse constructed from clear glass that eliminated approximately 15-20% of PAR intensity at noon. Light intensity in the greenhouse reached almost 1,000 µmol photons m^-2 s^-1 during sunny days, therefore it can still be regarded as fully saturating or excessive radiation, similar to that at outdoor conditions. Temperature in the greenhouse was lowered during the day by the automated ventilation, but air vents were closed during the night. Temperature in the greenhouse was substantially higher than outdoors (environmental conditions 1 and 2). During the experiment, the night temperature in the greenhouse ranged between 15 and 20 ℃ , whereas the daily maximum temperature oscillated mostly between 20 and 32 ℃ . The maximum temperature of 35 ℃ was reached during a few of the warmest days. In each environment, plants were grown in the randomized complete block design, with weekly rotations of plant positions. Four healthy, well-developed plants from each cultivar were selected for analyses from each of the three environments. Non-destructive analyses started 30 days after sowing and continued for another 30 days. The complete above-ground parts of the plants were harvested at the end of the experiment (60 days after sewing) and were used for destructive analyses.Comparison between environments is based on the assumption that the plants grown under the glass sheets outdoors were exposed to similar light and low UV conditions as the plants in the greenhouse, but the temperature conditions were similar to those in direct sunlight outdoors. By comparing accumulation of phenolic compounds in plants grown in the three environments, we could distinguish the effects caused by UV radiation from those caused by the temperature.

Increased accumulation of total phenolics, flavonoids, anthocyanins, and phenolic acids was observed in direct sunlight conditions outdoors as compared to the greenhouse conditions with low UV radiation, but elevated day and night temperatures. The level of UV radiation played a dominant role in the accumulation of flavonoids, anthocyanins and methoxycinnamic acid; while temperature was a major factor affecting concentrations of phenolic acids, mostly rosmarinic, p-anisic and vanillic acid. The concentrations of compounds estimated with the non-invasive fluorescence excitation ratio method were highly consistent with those obtained by standard analytical approaches.

Twelve cultivars of leaf-type lettuce (Lactuca sativa var. crispa) were selected for the study. This type of lettuce forms open heads with loose leaves that do not close to cover younger leaves. Six green-colored cultivars originated from Semo, a.s., Czech Republic (Dubagold, Zlatava, and Zoltan) and Bejo Zaden B.V., Netherlands (Aleppo, Biondonna, and Kiribati); six red-colored cultivars were also from Semo (Dubared, Roden, and Rosaura) and Bejo Zaden (Carmesi, Oakly, and Spectation). The experiments were performed in the spring period (April, May). Lettuce seeds were sown in plastic pots and germinated under standard laboratory conditions (ca. 21 ℃ , 12-hour photoperiod). After germination, the lettuce plants were transplanted into a growth chamber (air-conditioned box model MC1750 (Snijders Scientific, Tilburg, Netherlands) and grown under 14/10 h (day/night) photoperiod, 21/18 ℃ temperature, 60% humidity, and 250 µmol.m ^-2.s^-1 light intensity. The commercial peat substrate (Klasmann, Germany) was used (pH 6.0, nutrient content: N: 220 mg/L, P₂O₅: 110 mg/L, K₂O: 220 mg/L, Mg: 80 mg/L). Approximately at the stage of second, fully expanded, true leaf the plants were transplanted to 0.5 l pots and kept at the same conditions for seven days to recover. After recovery, the plants were transferred into one of the three experimental conditions described below. Plants were watered regularly to avoid drought stress. Considering a high level of nutrients in the substrate and a short duration of the experiments, no additional nutrition was applied to plants.The experiments were held at SAU in Nitra (48° 19′ 7″ N, 18° 4′ 55″ E, 144 m asl). To distinguish the effects of UV radiation from other environmental factors such as temperature, humidity, and light intensity, the plants were grown in three different environments: 1. direct sunlight (outdoor conditions with high UV), 2. under clear glass (outdoor conditions with low UV), and 3. greenhouse (indoor conditions with low UV).Plants grown under direct sunlight conditions were placed into a vegetation cage (a walk-in cage surrounded by the thin wire mesh from the top and side to protect the experimental plants against birds and animals) and exposed to almost unrestricted sunlight and ambient temperature and humidity. Plants were watered as needed to achieve a fully hydrated state. Temperature outdoors was monitored.Plants grown under clear glass were placed in similar environmental conditions as those cultivated under direct sunlight, but were grown in the glass shelter constructed from clear glass sheets (thickness of 8 mm). The clear glass sheets were positioned such as to eliminate UV light coming to plants from the south and above. The backside (oriented to the north) of this glass shelter was covered by the plastic-coated wire mesh not impeding the flow of air, so the temperature and other conditions were almost identical to fully open outdoor conditions. Temperature outdoors and under the glass sheets was occasionally compared using hand-held thermometers, showing only insignificant differences. The glass cover lowered the intensity of photosynthetically active radiation (PAR) by 10-15% at noon due to absorbance and reflectance of radiation by the glass. The overhang of the glass shelter, wire mesh from the north part as well as composition of buildings from the north west and east direction was very favorable to prevent excessive access of diffuse UV radiation. Thus, despite UV radiation is not fully eliminated, its level represents only a small fraction compared to the direct UV radiation incident to plants exposed to direct sunlight outdoors.Plants grown indoors were placed in a regular greenhouse constructed from clear glass that eliminated approximately 15-20% of PAR intensity at noon. Light intensity in the greenhouse reached almost 1,000 µmol photons m^-2 s^-1 during sunny days, therefore it can still be regarded as fully saturating or excessive radiation, similar to that at outdoor conditions. Temperature in the greenhouse was lowered during the day by the automated ventilation, but air vents were closed during the night. Temperature in the greenhouse was substantially higher than outdoors (environmental conditions 1 and 2). During the experiment, the night temperature in the greenhouse ranged between 15 and 20 ℃ , whereas the daily maximum temperature oscillated mostly between 20 and 32 ℃ . The maximum temperature of 35 ℃ was reached during a few of the warmest days. In each environment, plants were grown in the randomized complete block design, with weekly rotations of plant positions. Four healthy, well-developed plants from each cultivar were selected for analyses from each of the three environments. Non-destructive analyses started 30 days after sowing and continued for another 30 days. The complete above-ground parts of the plants were harvested at the end of the experiment (60 days after sewing) and were used for destructive analyses.Comparison between environments is based on the assumption that the plants grown under the glass sheets outdoors were exposed to similar light and low UV conditions as the plants in the greenhouse, but the temperature conditions were similar to those in direct sunlight outdoors. By comparing accumulation of phenolic compounds in plants grown in the three environments, we could distinguish the effects caused by UV radiation from those caused by the temperature.

Increased accumulation of total phenolics, flavonoids, anthocyanins, and phenolic acids was observed in direct sunlight conditions outdoors as compared to the greenhouse conditions with low UV radiation, but elevated day and night temperatures. The level of UV radiation played a dominant role in the accumulation of flavonoids, anthocyanins and methoxycinnamic acid; while temperature was a major factor affecting concentrations of phenolic acids, mostly rosmarinic, p-anisic and vanillic acid. The concentrations of compounds estimated with the non-invasive fluorescence excitation ratio method were highly consistent with those obtained by standard analytical approaches.

Twelve cultivars of leaf-type lettuce (Lactuca sativa var. crispa) were selected for the study. This type of lettuce forms open heads with loose leaves that do not close to cover younger leaves. Six green-colored cultivars originated from Semo, a.s., Czech Republic (Dubagold, Zlatava, and Zoltan) and Bejo Zaden B.V., Netherlands (Aleppo, Biondonna, and Kiribati); six red-colored cultivars were also from Semo (Dubared, Roden, and Rosaura) and Bejo Zaden (Carmesi, Oakly, and Spectation). The experiments were performed in the spring period (April, May). Lettuce seeds were sown in plastic pots and germinated under standard laboratory conditions (ca. 21 ℃ , 12-hour photoperiod). After germination, the lettuce plants were transplanted into a growth chamber (air-conditioned box model MC1750 (Snijders Scientific, Tilburg, Netherlands) and grown under 14/10 h (day/night) photoperiod, 21/18 ℃ temperature, 60% humidity, and 250 µmol.m ^-2.s^-1 light intensity. The commercial peat substrate (Klasmann, Germany) was used (pH 6.0, nutrient content: N: 220 mg/L, P₂O₅: 110 mg/L, K₂O: 220 mg/L, Mg: 80 mg/L). Approximately at the stage of second, fully expanded, true leaf the plants were transplanted to 0.5 l pots and kept at the same conditions for seven days to recover. After recovery, the plants were transferred into one of the three experimental conditions described below. Plants were watered regularly to avoid drought stress. Considering a high level of nutrients in the substrate and a short duration of the experiments, no additional nutrition was applied to plants.The experiments were held at SAU in Nitra (48° 19′ 7″ N, 18° 4′ 55″ E, 144 m asl). To distinguish the effects of UV radiation from other environmental factors such as temperature, humidity, and light intensity, the plants were grown in three different environments: 1. direct sunlight (outdoor conditions with high UV), 2. under clear glass (outdoor conditions with low UV), and 3. greenhouse (indoor conditions with low UV).Plants grown under direct sunlight conditions were placed into a vegetation cage (a walk-in cage surrounded by the thin wire mesh from the top and side to protect the experimental plants against birds and animals) and exposed to almost unrestricted sunlight and ambient temperature and humidity. Plants were watered as needed to achieve a fully hydrated state. Temperature outdoors was monitored.Plants grown under clear glass were placed in similar environmental conditions as those cultivated under direct sunlight, but were grown in the glass shelter constructed from clear glass sheets (thickness of 8 mm). The clear glass sheets were positioned such as to eliminate UV light coming to plants from the south and above. The backside (oriented to the north) of this glass shelter was covered by the plastic-coated wire mesh not impeding the flow of air, so the temperature and other conditions were almost identical to fully open outdoor conditions. Temperature outdoors and under the glass sheets was occasionally compared using hand-held thermometers, showing only insignificant differences. The glass cover lowered the intensity of photosynthetically active radiation (PAR) by 10-15% at noon due to absorbance and reflectance of radiation by the glass. The overhang of the glass shelter, wire mesh from the north part as well as composition of buildings from the north west and east direction was very favorable to prevent excessive access of diffuse UV radiation. Thus, despite UV radiation is not fully eliminated, its level represents only a small fraction compared to the direct UV radiation incident to plants exposed to direct sunlight outdoors.Plants grown indoors were placed in a regular greenhouse constructed from clear glass that eliminated approximately 15-20% of PAR intensity at noon. Light intensity in the greenhouse reached almost 1,000 µmol photons m^-2 s^-1 during sunny days, therefore it can still be regarded as fully saturating or excessive radiation, similar to that at outdoor conditions. Temperature in the greenhouse was lowered during the day by the automated ventilation, but air vents were closed during the night. Temperature in the greenhouse was substantially higher than outdoors (environmental conditions 1 and 2). During the experiment, the night temperature in the greenhouse ranged between 15 and 20 ℃ , whereas the daily maximum temperature oscillated mostly between 20 and 32 ℃ . The maximum temperature of 35 ℃ was reached during a few of the warmest days. In each environment, plants were grown in the randomized complete block design, with weekly rotations of plant positions. Four healthy, well-developed plants from each cultivar were selected for analyses from each of the three environments. Non-destructive analyses started 30 days after sowing and continued for another 30 days. The complete above-ground parts of the plants were harvested at the end of the experiment (60 days after sewing) and were used for destructive analyses.Comparison between environments is based on the assumption that the plants grown under the glass sheets outdoors were exposed to similar light and low UV conditions as the plants in the greenhouse, but the temperature conditions were similar to those in direct sunlight outdoors. By comparing accumulation of phenolic compounds in plants grown in the three environments, we could distinguish the effects caused by UV radiation from those caused by the temperature.

Increased accumulation of total phenolics, flavonoids, anthocyanins, and phenolic acids was observed in direct sunlight conditions outdoors as compared to the greenhouse conditions with low UV radiation, but elevated day and night temperatures. The level of UV radiation played a dominant role in the accumulation of flavonoids, anthocyanins and methoxycinnamic acid; while temperature was a major factor affecting concentrations of phenolic acids, mostly rosmarinic, p-anisic and vanillic acid. The concentrations of compounds estimated with the non-invasive fluorescence excitation ratio method were highly consistent with those obtained by standard analytical approaches.

Twelve cultivars of leaf-type lettuce (Lactuca sativa var. crispa) were selected for the study. This type of lettuce forms open heads with loose leaves that do not close to cover younger leaves. Six green-colored cultivars originated from Semo, a.s., Czech Republic (Dubagold, Zlatava, and Zoltan) and Bejo Zaden B.V., Netherlands (Aleppo, Biondonna, and Kiribati); six red-colored cultivars were also from Semo (Dubared, Roden, and Rosaura) and Bejo Zaden (Carmesi, Oakly, and Spectation). The experiments were performed in the spring period (April, May). Lettuce seeds were sown in plastic pots and germinated under standard laboratory conditions (ca. 21 ℃ , 12-hour photoperiod). After germination, the lettuce plants were transplanted into a growth chamber (air-conditioned box model MC1750 (Snijders Scientific, Tilburg, Netherlands) and grown under 14/10 h (day/night) photoperiod, 21/18 ℃ temperature, 60% humidity, and 250 µmol.m ^-2.s^-1 light intensity. The commercial peat substrate (Klasmann, Germany) was used (pH 6.0, nutrient content: N: 220 mg/L, P₂O₅: 110 mg/L, K₂O: 220 mg/L, Mg: 80 mg/L). Approximately at the stage of second, fully expanded, true leaf the plants were transplanted to 0.5 l pots and kept at the same conditions for seven days to recover. After recovery, the plants were transferred into one of the three experimental conditions described below. Plants were watered regularly to avoid drought stress. Considering a high level of nutrients in the substrate and a short duration of the experiments, no additional nutrition was applied to plants.The experiments were held at SAU in Nitra (48° 19′ 7″ N, 18° 4′ 55″ E, 144 m asl). To distinguish the effects of UV radiation from other environmental factors such as temperature, humidity, and light intensity, the plants were grown in three different environments: 1. direct sunlight (outdoor conditions with high UV), 2. under clear glass (outdoor conditions with low UV), and 3. greenhouse (indoor conditions with low UV).Plants grown under direct sunlight conditions were placed into a vegetation cage (a walk-in cage surrounded by the thin wire mesh from the top and side to protect the experimental plants against birds and animals) and exposed to almost unrestricted sunlight and ambient temperature and humidity. Plants were watered as needed to achieve a fully hydrated state. Temperature outdoors was monitored.Plants grown under clear glass were placed in similar environmental conditions as those cultivated under direct sunlight, but were grown in the glass shelter constructed from clear glass sheets (thickness of 8 mm). The clear glass sheets were positioned such as to eliminate UV light coming to plants from the south and above. The backside (oriented to the north) of this glass shelter was covered by the plastic-coated wire mesh not impeding the flow of air, so the temperature and other conditions were almost identical to fully open outdoor conditions. Temperature outdoors and under the glass sheets was occasionally compared using hand-held thermometers, showing only insignificant differences. The glass cover lowered the intensity of photosynthetically active radiation (PAR) by 10-15% at noon due to absorbance and reflectance of radiation by the glass. The overhang of the glass shelter, wire mesh from the north part as well as composition of buildings from the north west and east direction was very favorable to prevent excessive access of diffuse UV radiation. Thus, despite UV radiation is not fully eliminated, its level represents only a small fraction compared to the direct UV radiation incident to plants exposed to direct sunlight outdoors.Plants grown indoors were placed in a regular greenhouse constructed from clear glass that eliminated approximately 15-20% of PAR intensity at noon. Light intensity in the greenhouse reached almost 1,000 µmol photons m^-2 s^-1 during sunny days, therefore it can still be regarded as fully saturating or excessive radiation, similar to that at outdoor conditions. Temperature in the greenhouse was lowered during the day by the automated ventilation, but air vents were closed during the night. Temperature in the greenhouse was substantially higher than outdoors (environmental conditions 1 and 2). During the experiment, the night temperature in the greenhouse ranged between 15 and 20 ℃ , whereas the daily maximum temperature oscillated mostly between 20 and 32 ℃ . The maximum temperature of 35 ℃ was reached during a few of the warmest days. In each environment, plants were grown in the randomized complete block design, with weekly rotations of plant positions. Four healthy, well-developed plants from each cultivar were selected for analyses from each of the three environments. Non-destructive analyses started 30 days after sowing and continued for another 30 days. The complete above-ground parts of the plants were harvested at the end of the experiment (60 days after sewing) and were used for destructive analyses.Comparison between environments is based on the assumption that the plants grown under the glass sheets outdoors were exposed to similar light and low UV conditions as the plants in the greenhouse, but the temperature conditions were similar to those in direct sunlight outdoors. By comparing accumulation of phenolic compounds in plants grown in the three environments, we could distinguish the effects caused by UV radiation from those caused by the temperature.

Increased accumulation of total phenolics, flavonoids, anthocyanins, and phenolic acids was observed in direct sunlight conditions outdoors as compared to the greenhouse conditions with low UV radiation, but elevated day and night temperatures. The level of UV radiation played a dominant role in the accumulation of flavonoids, anthocyanins and methoxycinnamic acid; while temperature was a major factor affecting concentrations of phenolic acids, mostly rosmarinic, p-anisic and vanillic acid. The concentrations of compounds estimated with the non-invasive fluorescence excitation ratio method were highly consistent with those obtained by standard analytical approaches.

Twelve cultivars of leaf-type lettuce (Lactuca sativa var. crispa) were selected for the study. This type of lettuce forms open heads with loose leaves that do not close to cover younger leaves. Six green-colored cultivars originated from Semo, a.s., Czech Republic (Dubagold, Zlatava, and Zoltan) and Bejo Zaden B.V., Netherlands (Aleppo, Biondonna, and Kiribati); six red-colored cultivars were also from Semo (Dubared, Roden, and Rosaura) and Bejo Zaden (Carmesi, Oakly, and Spectation). The experiments were performed in the spring period (April, May). Lettuce seeds were sown in plastic pots and germinated under standard laboratory conditions (ca. 21 ℃ , 12-hour photoperiod). After germination, the lettuce plants were transplanted into a growth chamber (air-conditioned box model MC1750 (Snijders Scientific, Tilburg, Netherlands) and grown under 14/10 h (day/night) photoperiod, 21/18 ℃ temperature, 60% humidity, and 250 µmol.m ^-2.s^-1 light intensity. The commercial peat substrate (Klasmann, Germany) was used (pH 6.0, nutrient content: N: 220 mg/L, P₂O₅: 110 mg/L, K₂O: 220 mg/L, Mg: 80 mg/L). Approximately at the stage of second, fully expanded, true leaf the plants were transplanted to 0.5 l pots and kept at the same conditions for seven days to recover. After recovery, the plants were transferred into one of the three experimental conditions described below. Plants were watered regularly to avoid drought stress. Considering a high level of nutrients in the substrate and a short duration of the experiments, no additional nutrition was applied to plants.The experiments were held at SAU in Nitra (48° 19′ 7″ N, 18° 4′ 55″ E, 144 m asl). To distinguish the effects of UV radiation from other environmental factors such as temperature, humidity, and light intensity, the plants were grown in three different environments: 1. direct sunlight (outdoor conditions with high UV), 2. under clear glass (outdoor conditions with low UV), and 3. greenhouse (indoor conditions with low UV).Plants grown under direct sunlight conditions were placed into a vegetation cage (a walk-in cage surrounded by the thin wire mesh from the top and side to protect the experimental plants against birds and animals) and exposed to almost unrestricted sunlight and ambient temperature and humidity. Plants were watered as needed to achieve a fully hydrated state. Temperature outdoors was monitored.Plants grown under clear glass were placed in similar environmental conditions as those cultivated under direct sunlight, but were grown in the glass shelter constructed from clear glass sheets (thickness of 8 mm). The clear glass sheets were positioned such as to eliminate UV light coming to plants from the south and above. The backside (oriented to the north) of this glass shelter was covered by the plastic-coated wire mesh not impeding the flow of air, so the temperature and other conditions were almost identical to fully open outdoor conditions. Temperature outdoors and under the glass sheets was occasionally compared using hand-held thermometers, showing only insignificant differences. The glass cover lowered the intensity of photosynthetically active radiation (PAR) by 10-15% at noon due to absorbance and reflectance of radiation by the glass. The overhang of the glass shelter, wire mesh from the north part as well as composition of buildings from the north west and east direction was very favorable to prevent excessive access of diffuse UV radiation. Thus, despite UV radiation is not fully eliminated, its level represents only a small fraction compared to the direct UV radiation incident to plants exposed to direct sunlight outdoors.Plants grown indoors were placed in a regular greenhouse constructed from clear glass that eliminated approximately 15-20% of PAR intensity at noon. Light intensity in the greenhouse reached almost 1,000 µmol photons m^-2 s^-1 during sunny days, therefore it can still be regarded as fully saturating or excessive radiation, similar to that at outdoor conditions. Temperature in the greenhouse was lowered during the day by the automated ventilation, but air vents were closed during the night. Temperature in the greenhouse was substantially higher than outdoors (environmental conditions 1 and 2). During the experiment, the night temperature in the greenhouse ranged between 15 and 20 ℃ , whereas the daily maximum temperature oscillated mostly between 20 and 32 ℃ . The maximum temperature of 35 ℃ was reached during a few of the warmest days. In each environment, plants were grown in the randomized complete block design, with weekly rotations of plant positions. Four healthy, well-developed plants from each cultivar were selected for analyses from each of the three environments. Non-destructive analyses started 30 days after sowing and continued for another 30 days. The complete above-ground parts of the plants were harvested at the end of the experiment (60 days after sewing) and were used for destructive analyses.Comparison between environments is based on the assumption that the plants grown under the glass sheets outdoors were exposed to similar light and low UV conditions as the plants in the greenhouse, but the temperature conditions were similar to those in direct sunlight outdoors. By comparing accumulation of phenolic compounds in plants grown in the three environments, we could distinguish the effects caused by UV radiation from those caused by the temperature.

Increased accumulation of total phenolics, flavonoids, anthocyanins, and phenolic acids was observed in direct sunlight conditions outdoors as compared to the greenhouse conditions with low UV radiation, but elevated day and night temperatures. The level of UV radiation played a dominant role in the accumulation of flavonoids, anthocyanins and methoxycinnamic acid; while temperature was a major factor affecting concentrations of phenolic acids, mostly rosmarinic, p-anisic and vanillic acid. The concentrations of compounds estimated with the non-invasive fluorescence excitation ratio method were highly consistent with those obtained by standard analytical approaches.

Twelve cultivars of leaf-type lettuce (Lactuca sativa var. crispa) were selected for the study. This type of lettuce forms open heads with loose leaves that do not close to cover younger leaves. Six green-colored cultivars originated from Semo, a.s., Czech Republic (Dubagold, Zlatava, and Zoltan) and Bejo Zaden B.V., Netherlands (Aleppo, Biondonna, and Kiribati); six red-colored cultivars were also from Semo (Dubared, Roden, and Rosaura) and Bejo Zaden (Carmesi, Oakly, and Spectation). The experiments were performed in the spring period (April, May). Lettuce seeds were sown in plastic pots and germinated under standard laboratory conditions (ca. 21 ℃ , 12-hour photoperiod). After germination, the lettuce plants were transplanted into a growth chamber (air-conditioned box model MC1750 (Snijders Scientific, Tilburg, Netherlands) and grown under 14/10 h (day/night) photoperiod, 21/18 ℃ temperature, 60% humidity, and 250 µmol.m ^-2.s^-1 light intensity. The commercial peat substrate (Klasmann, Germany) was used (pH 6.0, nutrient content: N: 220 mg/L, P₂O₅: 110 mg/L, K₂O: 220 mg/L, Mg: 80 mg/L). Approximately at the stage of second, fully expanded, true leaf the plants were transplanted to 0.5 l pots and kept at the same conditions for seven days to recover. After recovery, the plants were transferred into one of the three experimental conditions described below. Plants were watered regularly to avoid drought stress. Considering a high level of nutrients in the substrate and a short duration of the experiments, no additional nutrition was applied to plants.The experiments were held at SAU in Nitra (48° 19′ 7″ N, 18° 4′ 55″ E, 144 m asl). To distinguish the effects of UV radiation from other environmental factors such as temperature, humidity, and light intensity, the plants were grown in three different environments: 1. direct sunlight (outdoor conditions with high UV), 2. under clear glass (outdoor conditions with low UV), and 3. greenhouse (indoor conditions with low UV).Plants grown under direct sunlight conditions were placed into a vegetation cage (a walk-in cage surrounded by the thin wire mesh from the top and side to protect the experimental plants against birds and animals) and exposed to almost unrestricted sunlight and ambient temperature and humidity. Plants were watered as needed to achieve a fully hydrated state. Temperature outdoors was monitored.Plants grown under clear glass were placed in similar environmental conditions as those cultivated under direct sunlight, but were grown in the glass shelter constructed from clear glass sheets (thickness of 8 mm). The clear glass sheets were positioned such as to eliminate UV light coming to plants from the south and above. The backside (oriented to the north) of this glass shelter was covered by the plastic-coated wire mesh not impeding the flow of air, so the temperature and other conditions were almost identical to fully open outdoor conditions. Temperature outdoors and under the glass sheets was occasionally compared using hand-held thermometers, showing only insignificant differences. The glass cover lowered the intensity of photosynthetically active radiation (PAR) by 10-15% at noon due to absorbance and reflectance of radiation by the glass. The overhang of the glass shelter, wire mesh from the north part as well as composition of buildings from the north west and east direction was very favorable to prevent excessive access of diffuse UV radiation. Thus, despite UV radiation is not fully eliminated, its level represents only a small fraction compared to the direct UV radiation incident to plants exposed to direct sunlight outdoors.Plants grown indoors were placed in a regular greenhouse constructed from clear glass that eliminated approximately 15-20% of PAR intensity at noon. Light intensity in the greenhouse reached almost 1,000 µmol photons m^-2 s^-1 during sunny days, therefore it can still be regarded as fully saturating or excessive radiation, similar to that at outdoor conditions. Temperature in the greenhouse was lowered during the day by the automated ventilation, but air vents were closed during the night. Temperature in the greenhouse was substantially higher than outdoors (environmental conditions 1 and 2). During the experiment, the night temperature in the greenhouse ranged between 15 and 20 ℃ , whereas the daily maximum temperature oscillated mostly between 20 and 32 ℃ . The maximum temperature of 35 ℃ was reached during a few of the warmest days. In each environment, plants were grown in the randomized complete block design, with weekly rotations of plant positions. Four healthy, well-developed plants from each cultivar were selected for analyses from each of the three environments. Non-destructive analyses started 30 days after sowing and continued for another 30 days. The complete above-ground parts of the plants were harvested at the end of the experiment (60 days after sewing) and were used for destructive analyses.Comparison between environments is based on the assumption that the plants grown under the glass sheets outdoors were exposed to similar light and low UV conditions as the plants in the greenhouse, but the temperature conditions were similar to those in direct sunlight outdoors. By comparing accumulation of phenolic compounds in plants grown in the three environments, we could distinguish the effects caused by UV radiation from those caused by the temperature.

Increased accumulation of total phenolics, flavonoids, anthocyanins, and phenolic acids was observed in direct sunlight conditions outdoors as compared to the greenhouse conditions with low UV radiation, but elevated day and night temperatures. The level of UV radiation played a dominant role in the accumulation of flavonoids, anthocyanins and methoxycinnamic acid; while temperature was a major factor affecting concentrations of phenolic acids, mostly rosmarinic, p-anisic and vanillic acid. The concentrations of compounds estimated with the non-invasive fluorescence excitation ratio method were highly consistent with those obtained by standard analytical approaches.

Twelve cultivars of leaf-type lettuce (Lactuca sativa var. crispa) were selected for the study. This type of lettuce forms open heads with loose leaves that do not close to cover younger leaves. Six green-colored cultivars originated from Semo, a.s., Czech Republic (Dubagold, Zlatava, and Zoltan) and Bejo Zaden B.V., Netherlands (Aleppo, Biondonna, and Kiribati); six red-colored cultivars were also from Semo (Dubared, Roden, and Rosaura) and Bejo Zaden (Carmesi, Oakly, and Spectation). The experiments were performed in the spring period (April, May). Lettuce seeds were sown in plastic pots and germinated under standard laboratory conditions (ca. 21 ℃ , 12-hour photoperiod). After germination, the lettuce plants were transplanted into a growth chamber (air-conditioned box model MC1750 (Snijders Scientific, Tilburg, Netherlands) and grown under 14/10 h (day/night) photoperiod, 21/18 ℃ temperature, 60% humidity, and 250 µmol.m ^-2.s^-1 light intensity. The commercial peat substrate (Klasmann, Germany) was used (pH 6.0, nutrient content: N: 220 mg/L, P₂O₅: 110 mg/L, K₂O: 220 mg/L, Mg: 80 mg/L). Approximately at the stage of second, fully expanded, true leaf the plants were transplanted to 0.5 l pots and kept at the same conditions for seven days to recover. After recovery, the plants were transferred into one of the three experimental conditions described below. Plants were watered regularly to avoid drought stress. Considering a high level of nutrients in the substrate and a short duration of the experiments, no additional nutrition was applied to plants.The experiments were held at SAU in Nitra (48° 19′ 7″ N, 18° 4′ 55″ E, 144 m asl). To distinguish the effects of UV radiation from other environmental factors such as temperature, humidity, and light intensity, the plants were grown in three different environments: 1. direct sunlight (outdoor conditions with high UV), 2. under clear glass (outdoor conditions with low UV), and 3. greenhouse (indoor conditions with low UV).Plants grown under direct sunlight conditions were placed into a vegetation cage (a walk-in cage surrounded by the thin wire mesh from the top and side to protect the experimental plants against birds and animals) and exposed to almost unrestricted sunlight and ambient temperature and humidity. Plants were watered as needed to achieve a fully hydrated state. Temperature outdoors was monitored.Plants grown under clear glass were placed in similar environmental conditions as those cultivated under direct sunlight, but were grown in the glass shelter constructed from clear glass sheets (thickness of 8 mm). The clear glass sheets were positioned such as to eliminate UV light coming to plants from the south and above. The backside (oriented to the north) of this glass shelter was covered by the plastic-coated wire mesh not impeding the flow of air, so the temperature and other conditions were almost identical to fully open outdoor conditions. Temperature outdoors and under the glass sheets was occasionally compared using hand-held thermometers, showing only insignificant differences. The glass cover lowered the intensity of photosynthetically active radiation (PAR) by 10-15% at noon due to absorbance and reflectance of radiation by the glass. The overhang of the glass shelter, wire mesh from the north part as well as composition of buildings from the north west and east direction was very favorable to prevent excessive access of diffuse UV radiation. Thus, despite UV radiation is not fully eliminated, its level represents only a small fraction compared to the direct UV radiation incident to plants exposed to direct sunlight outdoors.Plants grown indoors were placed in a regular greenhouse constructed from clear glass that eliminated approximately 15-20% of PAR intensity at noon. Light intensity in the greenhouse reached almost 1,000 µmol photons m^-2 s^-1 during sunny days, therefore it can still be regarded as fully saturating or excessive radiation, similar to that at outdoor conditions. Temperature in the greenhouse was lowered during the day by the automated ventilation, but air vents were closed during the night. Temperature in the greenhouse was substantially higher than outdoors (environmental conditions 1 and 2). During the experiment, the night temperature in the greenhouse ranged between 15 and 20 ℃ , whereas the daily maximum temperature oscillated mostly between 20 and 32 ℃ . The maximum temperature of 35 ℃ was reached during a few of the warmest days. In each environment, plants were grown in the randomized complete block design, with weekly rotations of plant positions. Four healthy, well-developed plants from each cultivar were selected for analyses from each of the three environments. Non-destructive analyses started 30 days after sowing and continued for another 30 days. The complete above-ground parts of the plants were harvested at the end of the experiment (60 days after sewing) and were used for destructive analyses.Comparison between environments is based on the assumption that the plants grown under the glass sheets outdoors were exposed to similar light and low UV conditions as the plants in the greenhouse, but the temperature conditions were similar to those in direct sunlight outdoors. By comparing accumulation of phenolic compounds in plants grown in the three environments, we could distinguish the effects caused by UV radiation from those caused by the temperature.

Increased accumulation of total phenolics, flavonoids, anthocyanins, and phenolic acids was observed in direct sunlight conditions outdoors as compared to the greenhouse conditions with low UV radiation, but elevated day and night temperatures. The level of UV radiation played a dominant role in the accumulation of flavonoids, anthocyanins and methoxycinnamic acid; while temperature was a major factor affecting concentrations of phenolic acids, mostly rosmarinic, p-anisic and vanillic acid. The concentrations of compounds estimated with the non-invasive fluorescence excitation ratio method were highly consistent with those obtained by standard analytical approaches.

Twelve cultivars of leaf-type lettuce (Lactuca sativa var. crispa) were selected for the study. This type of lettuce forms open heads with loose leaves that do not close to cover younger leaves. Six green-colored cultivars originated from Semo, a.s., Czech Republic (Dubagold, Zlatava, and Zoltan) and Bejo Zaden B.V., Netherlands (Aleppo, Biondonna, and Kiribati); six red-colored cultivars were also from Semo (Dubared, Roden, and Rosaura) and Bejo Zaden (Carmesi, Oakly, and Spectation). The experiments were performed in the spring period (April, May). Lettuce seeds were sown in plastic pots and germinated under standard laboratory conditions (ca. 21 ℃ , 12-hour photoperiod). After germination, the lettuce plants were transplanted into a growth chamber (air-conditioned box model MC1750 (Snijders Scientific, Tilburg, Netherlands) and grown under 14/10 h (day/night) photoperiod, 21/18 ℃ temperature, 60% humidity, and 250 µmol.m ^-2.s^-1 light intensity. The commercial peat substrate (Klasmann, Germany) was used (pH 6.0, nutrient content: N: 220 mg/L, P₂O₅: 110 mg/L, K₂O: 220 mg/L, Mg: 80 mg/L). Approximately at the stage of second, fully expanded, true leaf the plants were transplanted to 0.5 l pots and kept at the same conditions for seven days to recover. After recovery, the plants were transferred into one of the three experimental conditions described below. Plants were watered regularly to avoid drought stress. Considering a high level of nutrients in the substrate and a short duration of the experiments, no additional nutrition was applied to plants.The experiments were held at SAU in Nitra (48° 19′ 7″ N, 18° 4′ 55″ E, 144 m asl). To distinguish the effects of UV radiation from other environmental factors such as temperature, humidity, and light intensity, the plants were grown in three different environments: 1. direct sunlight (outdoor conditions with high UV), 2. under clear glass (outdoor conditions with low UV), and 3. greenhouse (indoor conditions with low UV).Plants grown under direct sunlight conditions were placed into a vegetation cage (a walk-in cage surrounded by the thin wire mesh from the top and side to protect the experimental plants against birds and animals) and exposed to almost unrestricted sunlight and ambient temperature and humidity. Plants were watered as needed to achieve a fully hydrated state. Temperature outdoors was monitored.Plants grown under clear glass were placed in similar environmental conditions as those cultivated under direct sunlight, but were grown in the glass shelter constructed from clear glass sheets (thickness of 8 mm). The clear glass sheets were positioned such as to eliminate UV light coming to plants from the south and above. The backside (oriented to the north) of this glass shelter was covered by the plastic-coated wire mesh not impeding the flow of air, so the temperature and other conditions were almost identical to fully open outdoor conditions. Temperature outdoors and under the glass sheets was occasionally compared using hand-held thermometers, showing only insignificant differences. The glass cover lowered the intensity of photosynthetically active radiation (PAR) by 10-15% at noon due to absorbance and reflectance of radiation by the glass. The overhang of the glass shelter, wire mesh from the north part as well as composition of buildings from the north west and east direction was very favorable to prevent excessive access of diffuse UV radiation. Thus, despite UV radiation is not fully eliminated, its level represents only a small fraction compared to the direct UV radiation incident to plants exposed to direct sunlight outdoors.Plants grown indoors were placed in a regular greenhouse constructed from clear glass that eliminated approximately 15-20% of PAR intensity at noon. Light intensity in the greenhouse reached almost 1,000 µmol photons m^-2 s^-1 during sunny days, therefore it can still be regarded as fully saturating or excessive radiation, similar to that at outdoor conditions. Temperature in the greenhouse was lowered during the day by the automated ventilation, but air vents were closed during the night. Temperature in the greenhouse was substantially higher than outdoors (environmental conditions 1 and 2). During the experiment, the night temperature in the greenhouse ranged between 15 and 20 ℃ , whereas the daily maximum temperature oscillated mostly between 20 and 32 ℃ . The maximum temperature of 35 ℃ was reached during a few of the warmest days. In each environment, plants were grown in the randomized complete block design, with weekly rotations of plant positions. Four healthy, well-developed plants from each cultivar were selected for analyses from each of the three environments. Non-destructive analyses started 30 days after sowing and continued for another 30 days. The complete above-ground parts of the plants were harvested at the end of the experiment (60 days after sewing) and were used for destructive analyses.Comparison between environments is based on the assumption that the plants grown under the glass sheets outdoors were exposed to similar light and low UV conditions as the plants in the greenhouse, but the temperature conditions were similar to those in direct sunlight outdoors. By comparing accumulation of phenolic compounds in plants grown in the three environments, we could distinguish the effects caused by UV radiation from those caused by the temperature.

Increased accumulation of total phenolics, flavonoids, anthocyanins, and phenolic acids was observed in direct sunlight conditions outdoors as compared to the greenhouse conditions with low UV radiation, but elevated day and night temperatures. The level of UV radiation played a dominant role in the accumulation of flavonoids, anthocyanins and methoxycinnamic acid; while temperature was a major factor affecting concentrations of phenolic acids, mostly rosmarinic, p-anisic and vanillic acid. The concentrations of compounds estimated with the non-invasive fluorescence excitation ratio method were highly consistent with those obtained by standard analytical approaches.

Twelve cultivars of leaf-type lettuce (Lactuca sativa var. crispa) were selected for the study. This type of lettuce forms open heads with loose leaves that do not close to cover younger leaves. Six green-colored cultivars originated from Semo, a.s., Czech Republic (Dubagold, Zlatava, and Zoltan) and Bejo Zaden B.V., Netherlands (Aleppo, Biondonna, and Kiribati); six red-colored cultivars were also from Semo (Dubared, Roden, and Rosaura) and Bejo Zaden (Carmesi, Oakly, and Spectation). The experiments were performed in the spring period (April, May). Lettuce seeds were sown in plastic pots and germinated under standard laboratory conditions (ca. 21 ℃ , 12-hour photoperiod). After germination, the lettuce plants were transplanted into a growth chamber (air-conditioned box model MC1750 (Snijders Scientific, Tilburg, Netherlands) and grown under 14/10 h (day/night) photoperiod, 21/18 ℃ temperature, 60% humidity, and 250 µmol.m ^-2.s^-1 light intensity. The commercial peat substrate (Klasmann, Germany) was used (pH 6.0, nutrient content: N: 220 mg/L, P₂O₅: 110 mg/L, K₂O: 220 mg/L, Mg: 80 mg/L). Approximately at the stage of second, fully expanded, true leaf the plants were transplanted to 0.5 l pots and kept at the same conditions for seven days to recover. After recovery, the plants were transferred into one of the three experimental conditions described below. Plants were watered regularly to avoid drought stress. Considering a high level of nutrients in the substrate and a short duration of the experiments, no additional nutrition was applied to plants.The experiments were held at SAU in Nitra (48° 19′ 7″ N, 18° 4′ 55″ E, 144 m asl). To distinguish the effects of UV radiation from other environmental factors such as temperature, humidity, and light intensity, the plants were grown in three different environments: 1. direct sunlight (outdoor conditions with high UV), 2. under clear glass (outdoor conditions with low UV), and 3. greenhouse (indoor conditions with low UV).Plants grown under direct sunlight conditions were placed into a vegetation cage (a walk-in cage surrounded by the thin wire mesh from the top and side to protect the experimental plants against birds and animals) and exposed to almost unrestricted sunlight and ambient temperature and humidity. Plants were watered as needed to achieve a fully hydrated state. Temperature outdoors was monitored.Plants grown under clear glass were placed in similar environmental conditions as those cultivated under direct sunlight, but were grown in the glass shelter constructed from clear glass sheets (thickness of 8 mm). The clear glass sheets were positioned such as to eliminate UV light coming to plants from the south and above. The backside (oriented to the north) of this glass shelter was covered by the plastic-coated wire mesh not impeding the flow of air, so the temperature and other conditions were almost identical to fully open outdoor conditions. Temperature outdoors and under the glass sheets was occasionally compared using hand-held thermometers, showing only insignificant differences. The glass cover lowered the intensity of photosynthetically active radiation (PAR) by 10-15% at noon due to absorbance and reflectance of radiation by the glass. The overhang of the glass shelter, wire mesh from the north part as well as composition of buildings from the north west and east direction was very favorable to prevent excessive access of diffuse UV radiation. Thus, despite UV radiation is not fully eliminated, its level represents only a small fraction compared to the direct UV radiation incident to plants exposed to direct sunlight outdoors.Plants grown indoors were placed in a regular greenhouse constructed from clear glass that eliminated approximately 15-20% of PAR intensity at noon. Light intensity in the greenhouse reached almost 1,000 µmol photons m^-2 s^-1 during sunny days, therefore it can still be regarded as fully saturating or excessive radiation, similar to that at outdoor conditions. Temperature in the greenhouse was lowered during the day by the automated ventilation, but air vents were closed during the night. Temperature in the greenhouse was substantially higher than outdoors (environmental conditions 1 and 2). During the experiment, the night temperature in the greenhouse ranged between 15 and 20 ℃ , whereas the daily maximum temperature oscillated mostly between 20 and 32 ℃ . The maximum temperature of 35 ℃ was reached during a few of the warmest days. In each environment, plants were grown in the randomized complete block design, with weekly rotations of plant positions. Four healthy, well-developed plants from each cultivar were selected for analyses from each of the three environments. Non-destructive analyses started 30 days after sowing and continued for another 30 days. The complete above-ground parts of the plants were harvested at the end of the experiment (60 days after sewing) and were used for destructive analyses.Comparison between environments is based on the assumption that the plants grown under the glass sheets outdoors were exposed to similar light and low UV conditions as the plants in the greenhouse, but the temperature conditions were similar to those in direct sunlight outdoors. By comparing accumulation of phenolic compounds in plants grown in the three environments, we could distinguish the effects caused by UV radiation from those caused by the temperature.

Increased accumulation of total phenolics, flavonoids, anthocyanins, and phenolic acids was observed in direct sunlight conditions outdoors as compared to the greenhouse conditions with low UV radiation, but elevated day and night temperatures. The level of UV radiation played a dominant role in the accumulation of flavonoids, anthocyanins and methoxycinnamic acid; while temperature was a major factor affecting concentrations of phenolic acids, mostly rosmarinic, p-anisic and vanillic acid. The concentrations of compounds estimated with the non-invasive fluorescence excitation ratio method were highly consistent with those obtained by standard analytical approaches.

Twelve cultivars of leaf-type lettuce (Lactuca sativa var. crispa) were selected for the study. This type of lettuce forms open heads with loose leaves that do not close to cover younger leaves. Six green-colored cultivars originated from Semo, a.s., Czech Republic (Dubagold, Zlatava, and Zoltan) and Bejo Zaden B.V., Netherlands (Aleppo, Biondonna, and Kiribati); six red-colored cultivars were also from Semo (Dubared, Roden, and Rosaura) and Bejo Zaden (Carmesi, Oakly, and Spectation). The experiments were performed in the spring period (April, May). Lettuce seeds were sown in plastic pots and germinated under standard laboratory conditions (ca. 21 ℃ , 12-hour photoperiod). After germination, the lettuce plants were transplanted into a growth chamber (air-conditioned box model MC1750 (Snijders Scientific, Tilburg, Netherlands) and grown under 14/10 h (day/night) photoperiod, 21/18 ℃ temperature, 60% humidity, and 250 µmol.m ^-2.s^-1 light intensity. The commercial peat substrate (Klasmann, Germany) was used (pH 6.0, nutrient content: N: 220 mg/L, P₂O₅: 110 mg/L, K₂O: 220 mg/L, Mg: 80 mg/L). Approximately at the stage of second, fully expanded, true leaf the plants were transplanted to 0.5 l pots and kept at the same conditions for seven days to recover. After recovery, the plants were transferred into one of the three experimental conditions described below. Plants were watered regularly to avoid drought stress. Considering a high level of nutrients in the substrate and a short duration of the experiments, no additional nutrition was applied to plants.The experiments were held at SAU in Nitra (48° 19′ 7″ N, 18° 4′ 55″ E, 144 m asl). To distinguish the effects of UV radiation from other environmental factors such as temperature, humidity, and light intensity, the plants were grown in three different environments: 1. direct sunlight (outdoor conditions with high UV), 2. under clear glass (outdoor conditions with low UV), and 3. greenhouse (indoor conditions with low UV).Plants grown under direct sunlight conditions were placed into a vegetation cage (a walk-in cage surrounded by the thin wire mesh from the top and side to protect the experimental plants against birds and animals) and exposed to almost unrestricted sunlight and ambient temperature and humidity. Plants were watered as needed to achieve a fully hydrated state. Temperature outdoors was monitored.Plants grown under clear glass were placed in similar environmental conditions as those cultivated under direct sunlight, but were grown in the glass shelter constructed from clear glass sheets (thickness of 8 mm). The clear glass sheets were positioned such as to eliminate UV light coming to plants from the south and above. The backside (oriented to the north) of this glass shelter was covered by the plastic-coated wire mesh not impeding the flow of air, so the temperature and other conditions were almost identical to fully open outdoor conditions. Temperature outdoors and under the glass sheets was occasionally compared using hand-held thermometers, showing only insignificant differences. The glass cover lowered the intensity of photosynthetically active radiation (PAR) by 10-15% at noon due to absorbance and reflectance of radiation by the glass. The overhang of the glass shelter, wire mesh from the north part as well as composition of buildings from the north west and east direction was very favorable to prevent excessive access of diffuse UV radiation. Thus, despite UV radiation is not fully eliminated, its level represents only a small fraction compared to the direct UV radiation incident to plants exposed to direct sunlight outdoors.Plants grown indoors were placed in a regular greenhouse constructed from clear glass that eliminated approximately 15-20% of PAR intensity at noon. Light intensity in the greenhouse reached almost 1,000 µmol photons m^-2 s^-1 during sunny days, therefore it can still be regarded as fully saturating or excessive radiation, similar to that at outdoor conditions. Temperature in the greenhouse was lowered during the day by the automated ventilation, but air vents were closed during the night. Temperature in the greenhouse was substantially higher than outdoors (environmental conditions 1 and 2). During the experiment, the night temperature in the greenhouse ranged between 15 and 20 ℃ , whereas the daily maximum temperature oscillated mostly between 20 and 32 ℃ . The maximum temperature of 35 ℃ was reached during a few of the warmest days. In each environment, plants were grown in the randomized complete block design, with weekly rotations of plant positions. Four healthy, well-developed plants from each cultivar were selected for analyses from each of the three environments. Non-destructive analyses started 30 days after sowing and continued for another 30 days. The complete above-ground parts of the plants were harvested at the end of the experiment (60 days after sewing) and were used for destructive analyses.Comparison between environments is based on the assumption that the plants grown under the glass sheets outdoors were exposed to similar light and low UV conditions as the plants in the greenhouse, but the temperature conditions were similar to those in direct sunlight outdoors. By comparing accumulation of phenolic compounds in plants grown in the three environments, we could distinguish the effects caused by UV radiation from those caused by the temperature.

Increased accumulation of total phenolics, flavonoids, anthocyanins, and phenolic acids was observed in direct sunlight conditions outdoors as compared to the greenhouse conditions with low UV radiation, but elevated day and night temperatures. The level of UV radiation played a dominant role in the accumulation of flavonoids, anthocyanins and methoxycinnamic acid; while temperature was a major factor affecting concentrations of phenolic acids, mostly rosmarinic, p-anisic and vanillic acid. The concentrations of compounds estimated with the non-invasive fluorescence excitation ratio method were highly consistent with those obtained by standard analytical approaches.

Twelve cultivars of leaf-type lettuce (Lactuca sativa var. crispa) were selected for the study. This type of lettuce forms open heads with loose leaves that do not close to cover younger leaves. Six green-colored cultivars originated from Semo, a.s., Czech Republic (Dubagold, Zlatava, and Zoltan) and Bejo Zaden B.V., Netherlands (Aleppo, Biondonna, and Kiribati); six red-colored cultivars were also from Semo (Dubared, Roden, and Rosaura) and Bejo Zaden (Carmesi, Oakly, and Spectation). The experiments were performed in the spring period (April, May). Lettuce seeds were sown in plastic pots and germinated under standard laboratory conditions (ca. 21 ℃ , 12-hour photoperiod). After germination, the lettuce plants were transplanted into a growth chamber (air-conditioned box model MC1750 (Snijders Scientific, Tilburg, Netherlands) and grown under 14/10 h (day/night) photoperiod, 21/18 ℃ temperature, 60% humidity, and 250 µmol.m ^-2.s^-1 light intensity. The commercial peat substrate (Klasmann, Germany) was used (pH 6.0, nutrient content: N: 220 mg/L, P₂O₅: 110 mg/L, K₂O: 220 mg/L, Mg: 80 mg/L). Approximately at the stage of second, fully expanded, true leaf the plants were transplanted to 0.5 l pots and kept at the same conditions for seven days to recover. After recovery, the plants were transferred into one of the three experimental conditions described below. Plants were watered regularly to avoid drought stress. Considering a high level of nutrients in the substrate and a short duration of the experiments, no additional nutrition was applied to plants.The experiments were held at SAU in Nitra (48° 19′ 7″ N, 18° 4′ 55″ E, 144 m asl). To distinguish the effects of UV radiation from other environmental factors such as temperature, humidity, and light intensity, the plants were grown in three different environments: 1. direct sunlight (outdoor conditions with high UV), 2. under clear glass (outdoor conditions with low UV), and 3. greenhouse (indoor conditions with low UV).Plants grown under direct sunlight conditions were placed into a vegetation cage (a walk-in cage surrounded by the thin wire mesh from the top and side to protect the experimental plants against birds and animals) and exposed to almost unrestricted sunlight and ambient temperature and humidity. Plants were watered as needed to achieve a fully hydrated state. Temperature outdoors was monitored.Plants grown under clear glass were placed in similar environmental conditions as those cultivated under direct sunlight, but were grown in the glass shelter constructed from clear glass sheets (thickness of 8 mm). The clear glass sheets were positioned such as to eliminate UV light coming to plants from the south and above. The backside (oriented to the north) of this glass shelter was covered by the plastic-coated wire mesh not impeding the flow of air, so the temperature and other conditions were almost identical to fully open outdoor conditions. Temperature outdoors and under the glass sheets was occasionally compared using hand-held thermometers, showing only insignificant differences. The glass cover lowered the intensity of photosynthetically active radiation (PAR) by 10-15% at noon due to absorbance and reflectance of radiation by the glass. The overhang of the glass shelter, wire mesh from the north part as well as composition of buildings from the north west and east direction was very favorable to prevent excessive access of diffuse UV radiation. Thus, despite UV radiation is not fully eliminated, its level represents only a small fraction compared to the direct UV radiation incident to plants exposed to direct sunlight outdoors.Plants grown indoors were placed in a regular greenhouse constructed from clear glass that eliminated approximately 15-20% of PAR intensity at noon. Light intensity in the greenhouse reached almost 1,000 µmol photons m^-2 s^-1 during sunny days, therefore it can still be regarded as fully saturating or excessive radiation, similar to that at outdoor conditions. Temperature in the greenhouse was lowered during the day by the automated ventilation, but air vents were closed during the night. Temperature in the greenhouse was substantially higher than outdoors (environmental conditions 1 and 2). During the experiment, the night temperature in the greenhouse ranged between 15 and 20 ℃ , whereas the daily maximum temperature oscillated mostly between 20 and 32 ℃ . The maximum temperature of 35 ℃ was reached during a few of the warmest days. In each environment, plants were grown in the randomized complete block design, with weekly rotations of plant positions. Four healthy, well-developed plants from each cultivar were selected for analyses from each of the three environments. Non-destructive analyses started 30 days after sowing and continued for another 30 days. The complete above-ground parts of the plants were harvested at the end of the experiment (60 days after sewing) and were used for destructive analyses.Comparison between environments is based on the assumption that the plants grown under the glass sheets outdoors were exposed to similar light and low UV conditions as the plants in the greenhouse, but the temperature conditions were similar to those in direct sunlight outdoors. By comparing accumulation of phenolic compounds in plants grown in the three environments, we could distinguish the effects caused by UV radiation from those caused by the temperature.

Increased accumulation of total phenolics, flavonoids, anthocyanins, and phenolic acids was observed in direct sunlight conditions outdoors as compared to the greenhouse conditions with low UV radiation, but elevated day and night temperatures. The level of UV radiation played a dominant role in the accumulation of flavonoids, anthocyanins and methoxycinnamic acid; while temperature was a major factor affecting concentrations of phenolic acids, mostly rosmarinic, p-anisic and vanillic acid. The concentrations of compounds estimated with the non-invasive fluorescence excitation ratio method were highly consistent with those obtained by standard analytical approaches.

Twelve cultivars of leaf-type lettuce (Lactuca sativa var. crispa) were selected for the study. This type of lettuce forms open heads with loose leaves that do not close to cover younger leaves. Six green-colored cultivars originated from Semo, a.s., Czech Republic (Dubagold, Zlatava, and Zoltan) and Bejo Zaden B.V., Netherlands (Aleppo, Biondonna, and Kiribati); six red-colored cultivars were also from Semo (Dubared, Roden, and Rosaura) and Bejo Zaden (Carmesi, Oakly, and Spectation). The experiments were performed in the spring period (April, May). Lettuce seeds were sown in plastic pots and germinated under standard laboratory conditions (ca. 21 ℃ , 12-hour photoperiod). After germination, the lettuce plants were transplanted into a growth chamber (air-conditioned box model MC1750 (Snijders Scientific, Tilburg, Netherlands) and grown under 14/10 h (day/night) photoperiod, 21/18 ℃ temperature, 60% humidity, and 250 µmol.m ^-2.s^-1 light intensity. The commercial peat substrate (Klasmann, Germany) was used (pH 6.0, nutrient content: N: 220 mg/L, P₂O₅: 110 mg/L, K₂O: 220 mg/L, Mg: 80 mg/L). Approximately at the stage of second, fully expanded, true leaf the plants were transplanted to 0.5 l pots and kept at the same conditions for seven days to recover. After recovery, the plants were transferred into one of the three experimental conditions described below. Plants were watered regularly to avoid drought stress. Considering a high level of nutrients in the substrate and a short duration of the experiments, no additional nutrition was applied to plants.The experiments were held at SAU in Nitra (48° 19′ 7″ N, 18° 4′ 55″ E, 144 m asl). To distinguish the effects of UV radiation from other environmental factors such as temperature, humidity, and light intensity, the plants were grown in three different environments: 1. direct sunlight (outdoor conditions with high UV), 2. under clear glass (outdoor conditions with low UV), and 3. greenhouse (indoor conditions with low UV).Plants grown under direct sunlight conditions were placed into a vegetation cage (a walk-in cage surrounded by the thin wire mesh from the top and side to protect the experimental plants against birds and animals) and exposed to almost unrestricted sunlight and ambient temperature and humidity. Plants were watered as needed to achieve a fully hydrated state. Temperature outdoors was monitored.Plants grown under clear glass were placed in similar environmental conditions as those cultivated under direct sunlight, but were grown in the glass shelter constructed from clear glass sheets (thickness of 8 mm). The clear glass sheets were positioned such as to eliminate UV light coming to plants from the south and above. The backside (oriented to the north) of this glass shelter was covered by the plastic-coated wire mesh not impeding the flow of air, so the temperature and other conditions were almost identical to fully open outdoor conditions. Temperature outdoors and under the glass sheets was occasionally compared using hand-held thermometers, showing only insignificant differences. The glass cover lowered the intensity of photosynthetically active radiation (PAR) by 10-15% at noon due to absorbance and reflectance of radiation by the glass. The overhang of the glass shelter, wire mesh from the north part as well as composition of buildings from the north west and east direction was very favorable to prevent excessive access of diffuse UV radiation. Thus, despite UV radiation is not fully eliminated, its level represents only a small fraction compared to the direct UV radiation incident to plants exposed to direct sunlight outdoors.Plants grown indoors were placed in a regular greenhouse constructed from clear glass that eliminated approximately 15-20% of PAR intensity at noon. Light intensity in the greenhouse reached almost 1,000 µmol photons m^-2 s^-1 during sunny days, therefore it can still be regarded as fully saturating or excessive radiation, similar to that at outdoor conditions. Temperature in the greenhouse was lowered during the day by the automated ventilation, but air vents were closed during the night. Temperature in the greenhouse was substantially higher than outdoors (environmental conditions 1 and 2). During the experiment, the night temperature in the greenhouse ranged between 15 and 20 ℃ , whereas the daily maximum temperature oscillated mostly between 20 and 32 ℃ . The maximum temperature of 35 ℃ was reached during a few of the warmest days. In each environment, plants were grown in the randomized complete block design, with weekly rotations of plant positions. Four healthy, well-developed plants from each cultivar were selected for analyses from each of the three environments. Non-destructive analyses started 30 days after sowing and continued for another 30 days. The complete above-ground parts of the plants were harvested at the end of the experiment (60 days after sewing) and were used for destructive analyses.Comparison between environments is based on the assumption that the plants grown under the glass sheets outdoors were exposed to similar light and low UV conditions as the plants in the greenhouse, but the temperature conditions were similar to those in direct sunlight outdoors. By comparing accumulation of phenolic compounds in plants grown in the three environments, we could distinguish the effects caused by UV radiation from those caused by the temperature.

Increased accumulation of total phenolics, flavonoids, anthocyanins, and phenolic acids was observed in direct sunlight conditions outdoors as compared to the greenhouse conditions with low UV radiation, but elevated day and night temperatures. The level of UV radiation played a dominant role in the accumulation of flavonoids, anthocyanins and methoxycinnamic acid; while temperature was a major factor affecting concentrations of phenolic acids, mostly rosmarinic, p-anisic and vanillic acid. The concentrations of compounds estimated with the non-invasive fluorescence excitation ratio method were highly consistent with those obtained by standard analytical approaches.

Seeds were sterilized in 1% (v/v) sodium hypochloride (Sigma-Aldrich, USA) for 10 min, then drained and washed with distilled water until they reached neutral pH. They were placed in distilled water and soaked for 6 h at 25 ℃ . Seeds were dark germinated for 8 days in a growth chamber (SANYO MLR-350H) on Petri dishes (125 mm) lined with absorbent paper. Seedlings were watered with 5 ml of Milli-Q water daily. Sprout (8-day-old) samples were gently collected, weighed (fresh mass), rapidly frozen and kept in polyethylene bags at -20 ℃ . For each treatment, three replicates were performed.Elicitation conditions were selected in previous screening studies. For the experiments, temperature (4 ℃ and 40 ℃ - TC and TH, respectively), H₂O2 (20 mM and 200 mM - Ox1 and Ox2, respectively), mannitol (200 mM and 600 mM - Os1 and Os2, respectively) and NaCl (100 mM and 300 mM - S-Os1 and S-Os2, respectively) were selected as abiotic elicitors. All solutions were freshly prepared before each application. Mannitol (Os1, Os2), NaCl (S-O1, S-O2) and H₂O2 (Ox1) treatments were applied by watering daily (not soaking) 2-day-old sprouts with 5 ml of test solution. For Ox2 (200 mM H₂O2) treatment 2-day-old seedlings were only once watered with 5 ml of 200 mM H₂O2 and then cultivated under standard conditions. For temperature conditioning treatment, 2-day-old sprouts were incubated at 4 ℃ and 40 ℃ (TC and TH, respectively) for 1 h and then cultivated under standard conditions. Sprout (8-day-old) samples were gently collected, weighed (fresh mass), rapidly frozen and kept in polyethylene bags at -20 ℃ .

Application of abiotic elicitors (environmental shocks) was an effective method for improvement of sprout pro-health potential via an increase of phenolic contents and subsequent elevation of antioxidant potential. Innovative application of elicitors on 2-day-old sprouts (not seed) allowed the elimination of the unfavorable influence of the factors employed on germination yield and biomass production. Assuming that the optimal germination conditions are those which most effectively increase the antioxidant potential without any negative influence on biomass accumulation and nutritional quality the elicitation with 20 mM H₂O₂ for the future applications is recommended.

Peach fruit (Prunus persica Batsch cv. 'Yuhua No. 2') was hand-harvested at commercial maturity (about 9-12N firmness, 10-12% total soluble solids) from a local orchard in Nanjing, China. The fresh weight of 'Yuhua No. 2' peach is about 215g and the dry weight is about 30g. The fruit shape is round and the diameter size is about 72 mm. The peaches were selected in uniform size and color and absence of any damage. The selected peaches were randomly divided into two groups, each with 360 fruits for 3 replicates. According to our previous study, 10 mmol/LGB was selected as the treatment concentration. Peach fruits were immersed in 10 mmol/LGB solution for 10 min to ensure that GB could be equally distributed on the fruits. The control fruits were soaked in sterile deionized water for 10 min. After treatment, all fruits were air dried about 30 min and stored at 0℃ with a relative humidity of 85-90% for 35 days. Mesocarp samples were collected from 18 fruits on the 7th, 14th, 21th, 28th, 35th day and frozen in liquid nitrogen, then stored at -80℃ until biochemical analysis. Another 18 fruits were removed from 0℃ after 7th, 14th, 21th, 28th, 35th day, and held at 20℃ for three days to simulate shelf condition, and then evaluated CI index, firmness and extractable juice. Each treatment was replicated three times and the experiment was conducted twice with similar results.

Glycine betaine (GB) treatment enhanced chilling tolerance throughout regulating phenolic and sugar metabolisms in peach fruit during cold storage. The alleviation of chilling injury (CI) by GB treatment may be attributed to enhancement of individual of phenolic compounds and sucrose content, and induce the activities of enzymes related to phenolic and sugar metabolisms.

The experiment was carried out in 2013. Leaves of five raspberry cultivars ('Polana', 'Polka', 'Tulameen', 'Laszka' and 'Glen Ample') were collected at the time of cultivation. Three organic and neighborhood conventional farms were used for experimental purposes. From one cultivar (one field plot), 3-4 plants were chosen, which were analyzed separately. One sample consisted of 10 leaves. The farm was treated as a replication. [organic farm no. 1 Localization: akroczym(52° 26″ N 20° 36″ E), Type of Soil: sandy middle soil IVa and IVb category (15% floatable particles) pH 5.5, Kind of Fertilizer: cow manure, Dose of Fertilizers and Time of Given: 35 t/ha one year before raspberry planting, Plant Protection System: Grevit 200 SL; organic farm no. 2 Localization: Zaluski (52° 37″ N 20° 22″ E), Type of Soil: sandy middle soil, sandy-clay IV category (20% floatable particles), pH 5.5, Kind of Fertilizer:cow manure, Dose of Fertilizers and Time of Given: 30 t/ha one year before raspberry planting, Plant Protection System: no protection; organic farm no. 3 Localization: Radzanow(51° 33″ N 20° 51″ E), Type of Soil: sandy middle soil IVa and III category (10% floatable particles), pH 6.0, Kind of Fertilizer:sheep manure, green manure, Dose of Fertilizers and Time of Given: 10 t/ha and 15 t/ha one year before raspberry planting, Plant Protection System: Bioczos 33 SL, Grevit 200 SL; conventional farm no. 1 Localization: Czerwinsk nad Wisla (52° 23″ N 20° 20″ E), Type of Soil: sandy-loamy middle soil IV and III category (20% floatable particles), pH 5.5, Kind of Fertilizer: Hydrocomplex 12-11-18; Superba 8-11-36, Dose of Fertilizers and Time of Given: (200 kg/ha, 150 kg/ha) in autumn a year before raspberry planting; 3 doses in time of cultivation, Plant Protection System: Signum 33 WG, Miros 20 SP; conventional farm no. 2 Localization: Czerwinsk nad Wisla (52° 23″ N 20° 20″ E), Type of Soil: sandy-loamy middle soil IV and III category (25% floatable particles), pH 5.5, Kind of Fertilizer: amonium nitrate, polyphosphate, magnesium sulphate, Dose of Fertilizers and Time of Given: in autumn a year before raspberry planting; 3 doses in time of cultivation, Plant Protection System: Calypso 480 SC, Miros 20 SP, Zato 50 WG; conventional farm no. 3 Localization: Czerwinsk nad Wisla(52° 25″ N 20° 23″ E), Type of Soil: sandy-clay middle soil II and III category (20% floatable particles) pH 6.0, Kind of Fertilizer:Rosafert 5-12-24-3, Dose of Fertilizers and Time of Given: 250 kg/ha in autumn a year before raspberry planting; 4 doses in time of cultivation, Plant Protection System: Calypso 480 SC, Miros 20 SP, Zato 50 WG].

Compared with conventional raspberry leaves, organic raspberry leaves were characterized by a significantly higher content of dry matter, total polyphenols, total phenolic acids, chlorogenic acid, caffeic acid, salicylic acid and quercetin-3-O-rutinoside; moreover, the organic leaves were characterized by higher antioxidant activity. Among examined cultivars, 'Polka' c. was characterized by the highest antioxidant status. However, raspberry leaves from conventional farms contained more total carotenoids, violaxanthin, alpha-carotene, beta-carotene, total chlorophyll and individual forms of chlorophylls: a and b.

Different concentrations of TiO₂ NPs (0, 10, 20, 30, and 50) were prepared for hairy root treatments. 0.5 g of .S. officinalis hairy roots were transferred to 250 mL Erlenmeyer flasks containing 15 mL of liquid MS culture medium with three replicates. Then, they were placed in an incubator shaker at 110 rpm and 25 &#8451 in dark conditions. On the 22nd day, the liquid MS culture media containing different concentrations of nano titanium dioxide was added to Erlenmeyer flasks. 24 and 48 h after treatment, the hairy roots were taken out and transferred to the MS culture medium lacking elicitor.

The highest rate of total phenol (9.79 mg GLA/g FW) and total flavonoid contents (1.06 mg QE/g FW) were obtained in the treated hairy roots with 50 and 30 mg/L of nano elicitor in 24 and 48 h of treatments, respectively. The maximum level of most polyphenols, such as rosmarinic acid, cinnamic acid, and rutin, was produced in 24 h of treatment. The use of TiO₂ NP for 48 h with 50 mg/L concentration showed the highest production level of SO6 protein.