Flavonoids and related phenolic compounds produced in the first internode of Sorghum vulgare Pers. in darkness and in light.

Abstract

Four-day-old first inter-nodes of S. vulgare var. Wheatland milo, grown in complete darkness, contained little or not detectable flavonoids, although Cg phenolic compounds and dhurrin were relatively abundant. After subsequent dark or light treatment, 4 flavonoids could be identified in the non-growing portions of either intact or excised internodes. Evidence was based on solubility characteristics, color reactions, RF values, and spectrophotometric data. Three were forms of anthocyanidins, the acylated cyanidin-3-glucoside studied by previous workers, and apigeninidin and luteolinidin which existed as the aglycone, the 5-glucoside, and an unidentified acid stable form. The 4th was probably the flavone, luteolin. All pigments became labelled when tissues were incubated with DL-phenylalanine-3-C14. White light of high intensity was obligatory for the production after 12-24 hours of the red cyanidin glycoside in 4-day-old intact or excised internodes from dark grown seedlings. But only an incubation in the dark for 48 hours in addition to the initial 4 days of growth in the dark was necessary for the synthesis of all 3 forms of apigenindin and luteolinidin. Light, therefore, was not required for the synthesis of C15 compounds or for the flavylium cation, although it may have accelerated their formation. There was an indication that light favored the synthesis of the B-ring substituted with hydroxyl groups in both the 3[image] and 4[image] positions, because the production of luteolinidin in light was greater than that of apigeninidin, and luteolin has been detected only after treatment with light of at least a low intensity.