| Abstract
| - The objective of the present study was to determine whether concentrations of different isoflavones(puerarin, genistein, genistin, daidzein, and daidzin) in shoots and roots of five selected soybeangenotypes would respond the same or differently to red (650 nm peak transmittance) and far-red(750 nm peak transmittance) light treatments given under controlled environments. Levels ofisoflavones (mg g-1 dry weight biomass) present in seeds, control roots, and shoots and 10 daylight-treated seedlings (light, dark, red, and far-red wavelengths) of soybean (Glycine max) weredetermined by high-performance liquid chromatography analysis in comparison with known isoflavonestandards. Seeds of the five soybean genotypes studied consistently stored most of their isoflavonesas glucosyl conjugates (e.g., daidzin, genistin, and puerarin). For the five soybean genotypes,isoflavone levels were lower in the seeds as compared with roots plus shoots of control, time zero(first true leaf stage) seedlings. Following 10 days of the respective light treatments, we found that(i) isoflavone levels were enhanced in dark-grown plants over light-grown plants for three of the fivegenotypes (a new finding) and the reverse occurred for a single genotype (a typical response oflegumes) and (ii) generally, far-red end of day (EOD) light treatment enhanced total isoflavone levelsin roots plus shoots over red EOD light treatment. Results from the present study show thatphytochrome does appear to play a role in regulating isoflavone levels in developing soybean seedlingsand that this influence by red/far-red-mediated phytochrome reactions is strongly dependent on thegenotypes selected for study. Keywords: Glycine max; soybean; isoflavones; red/far-red-mediated phytochrome reactions
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