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.

Plant material and horticultural practice: The experiments were conducted at the Universidade Federal de Lavras between November 2005 and January 2006. Seeds of O. selloi were sown in commercial substrate [Plantmax (Eucatex, Sao Paulo, SP, Brazil)] contained in 72-cell plastic trays and maintained in the greenhouse under intermittent nebulization for 60 days. Seedlings were transplanted to 10 L pots containing a substrate consisting of soil, matured cattle manure and sand (5:3:2), and cultivated under three different light regimes, namely, full sunlight, and sunlight with blue or red shading. Each treatment was repeated seven times and two plants were employed per repetition.

The compositions of the oils varied according to the quality of light. Although the qualitative profiles of the oils of plants grown under full sunlight or red shading were similar, that obtained from plants grown under blue shading presented a larger number of constituents. The highest level of methyl chavicol (93.2%), the major component of the oil, was observed in plants grown under full sunlight.