ISOFLAVONOIDS IN ROOT AND HYPOCOTYL OF SOYBEAN SEEDLINGS (GLYCINE-MAX, FABACEAE)

Isoflavonoids, some of which are highly fluorescent, are produced by s oybean [Glycine max (L.) Merr.] and serve as chemical signals for cert ain aspects of nitrogen fixation and microbial resistance. This study was conducted to determine whether soybean mutants with nonfluorescent roots contained abnormal concentrations of isoflavonoids. Isoflavonoi ds were extracted from the root and hypocotyl of 4-d-old wild-type soy bean seedlings (cv. Hark) having fluorescent roots and from four nonal lelic mutant, near isogenic lines of Hark having nonfluorescent roots. In addition, isoflavonoids were extracted from the root and hypocotyl of 4-d-old seedlings of near isogenic lines of Hark harboring two pai rs of the mutant alleles for nonfluorescent roots. Malonyl daidzin, da idzin, malonyl genistin, and genistein were the most abundant isoflavo noids extracted from either the root or hypocotyl of seedlings with ei ther fluorescent or nonfluorescent roots. Extracted malonyl daidzin, m alonyl genistin, and malonyl glycitin decomposed readily, yielding dai dzin, genistin, and glycitin, respectively. The concentrations of malo nyl genistin and genistein, two highly fluorescent compounds, were sim ilar in both fluorescent and nonfluorescent roots. Thus, root fluoresc ence was not correlated with abundance per se of fluorescent isoflavon oids in roots. In addition, the abundance of isoflavonoids extractable from the hypocotyl did not correlate with root fluorescence.