In vitro cultivation of Arabidopsis wildtype and mutant plants: Seeds were sterilized according to standard lab routines (EtOH, NaOCl/NaOH) prior to aseptical (in vitro) cultivation in 500 ml screw cap jars on MS medium (4.3 g/l; 50 ml/jar) containing Bacto- and Phytoagar (1:2; 6 g/l) and 30 g/l sucrose. Ten seeds were pipetted into each jar and plants grown for 6 weeks until flowering at a temperature of 20 ℃ under a 16/8 h day/ night regime using fluorescent tubes (Osram Lumilux Plus Eco 36 W). Both Arabidopsis thaliana wildtype plants of ecotype Columbia-0 (Col) and 4 Col-derived T-DNA knock-out mutants (homozygous lines) showing deficiencies in the GLS biosynthesis pathway were used in this study (five parallels for wildtype and mutants): TGG1 (Atg526000; Salk_130469), TGG2 (At5g25980; Salk_038730), Cyp83A1 (At4g13770) and Cyp83B1 (At4g31500; Salk_028573). Greenhouse-cultivation of Arabidopsis ecotypes: The following Arabidopsis ecotypes were used in the study: Columbia (Col), Cape Verde Islands (Cvi), Landsberg erecta (Ler) and Wassilewskija (Ws). Single plants were greenhouse-cultivated on fertilized soil (P-Jord; Emmaljunga Torvmull AB) in plug trays (9 × 6 cells) at a temperature of 20 ℃ (three parallels for each ecotype). Due to the 6-weeks growth period (November/December 2003), the plants were cultivated under a 16/8 h day/night regime using metal halide lamps (Osram HQI-T 400 W) placed 130 cm above the trays. Depending on the ecotypical plant development, whole plants were sampled after 3-4 weeks right before bolting for in vivo studies, while investigations of single plant organs (leaf, stem, inflorescence) were carried out after 5-6 weeks of cultivation.

Metabolites from methionine, leucine and phenylalanine-derived glucosinolates were most abundant (4-methylthiobutyl, 4-methylpentyl, 2-phenylethyl). In addition, 24 monoterpenes, 26 sesquiterpenes and 12 aromatic structures, predominantly observed in inflorescenses, are described. Excluding the vast group of straight chain aliphatic structures, a total of 102 volatile compounds were detected, of which 59 are reported in Arabidopsis thaliana for the first time, thus emphasizing the sensitivity and applicability of solid-phase microextraction for volatile profiling of plant secondary metabolites.

3-year old single shoot V. vinifera plants (cultivar Pinot noir 18 Gm grafted on Kober 5BB, 51 plants) potted in 3L pots in a sandy loam soil were used. All plants were well watered (200 mL per day) at the beginning of the experiment (04.06.2010; DAY 0; 5 plants) and water was supplied to all control plants once every day (250 mL per day), whereas water supply of stressed plants was stopped. Physiological measurements and sampling of leaves took place on 07.06.2010 (DAY 3; 5 control, 5 stressed plants), 10.06.2010 (DAY 6; 5 control, 5 stressed plants) and 12.06.2010 (DAY 8; 5 control, 10 stressed plants). Due to very hot weather conditions in June 2010 the experiment was stopped after 8 days and 12 available control plants were used to restart the drought treatment with 6 control and 6 stressed plants on 11.06.2010 and all plants were measured on 15.06.2010 (DAY 5). The mean leaf temperatures at midday were: 25 ℃ (04.06.2010; DAY 0), 31.9 ℃ (07.06.2010; DAY 3), 30.8 ℃ (15.06.2010; DAY 5), 35.8 ℃ (10.06.2010; DAY 6) and 35.7 ℃ (12.06.2010; DAY 8). The mean PAR radiation per day (measured from 6:00 am till 7:00 pm) was 144.1 µmol m^-2 s^-1. Each plant was used only once for physiological measurements and sampling of leaves.On every day of the experiment (day 0, 3, 5, 6, 8) the pot weight and the volumetric soil moisture content (ThetaProbe ML2x and handheld data logger Moisture Meter HH2, Delta-T Devices, Cambridge, United Kingdom) was recorded. The water potential (PWSC Model 3000, Soilmoisture Equipment Corporation, Santa Barbara, USA) was determined for the 6th leaf (representing the insertion level of the shoot from the basis) of every plant and measurement day. Chlorophyll fluorescence and gas exchange parameters of light adapted leaves were determined with the 4th and 5th leaf, whereas dark adaptation was performed only with the 5th leaf. Immediately after these non-invasive measurements, the 5th leaf was harvested, frozen in liquid nitrogen and further used for the measurement of polyphenols, selected primary metabolites and volatiles (VOCs).

The content of different groups of primary and secondary metabolites is significantly influenced by severe drought stress in grapevine leaves. The content of the majority of the metabolites (around 60% of primary metabolites, around 85% of polyphenols and about 40% of the detected and identified VOCs) increased upon drought stress treatment. Among these especially the primary metabolites citric acid and glyceric acid were strongly influenced by the short as well as the prolonged drought stress treatment, whereas all polyphenols were only induced upon the prolonged drought stress treatment.