Photocontrol of Spirodela intermedia flavonoids

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Abstract
Clone 115 of SpirodelaUitermedia W. Koch grown in Hutner''s medium with sucrose produces the glyco-f lav ones vitexin and orientin in darkness or in light of various wave lengths. The anthocyanin cyanidin-3-monoglucoside was present only after prolonged illumination of the plants with white or blue light. No cyanidin-glucoside was formed under constant red light. The substitution of red, blue, or far-red light for the last 24 hr. of culture under constant white light reduced each f lavonoid over those maintained in white light or given 24 hours of darkness. Reducing the light intensity from 900 to 400 ft-c of constant cool-white fluorescent light had no appreciable influence on vitexin (4[image]-hydroxyl) but markedly reduced orientin and cyanidin-glucoside (both 3[image]4[image]-hydroxyl). Substituting alternate 12-hr. periods of light and darkness for continuous light reduced the glycoflavones approximately 50% while cyanidin-glucoside was reduced about 85%. Most responses to red, blue, or far-red light are consistent with a phytochrome-controlled promotion of vitexin synthesis. The evidence suggests that in S. intermedia: environmental conditions which elicit cyanidin-glucoside and glycoflavone synthesis are different since a prolonged illumination with white light is required for the former but not the latter; the availability of a 3[image]4[image]-hydroxyl precursor for orientin and anthocyanin probably limits their synthesis in low intensity light. Since vitexin is essentially unaltered under these conditions this also suggests that acetate or malonate units for the A-ring and the deamination products of aromatic amino acids for the firing and carbons of the C-ring are not limiting factors; light controls the biosynthesis of flavonols in the same manner as glycoflavones; under all experimental conditions the synthesis of kaempferol paralleled vitexin while quercetin responded in the same manner as crientin.