Effect of Light on Flavonoids Biosynthesis in Red Rice Rdh

The effect of light on flavonoids biosynthesis in red rice Rdh was studied. The panicles of red rice Rdh produced colorless caryopses after darkness treatment; and these colorless caryopses displayed bright-red after vanillin treatment, but did not display red color after light inducing for 15 days, suggesting that red rice Rdh could produce leucoanthocyanidin, but could not produce polyproanthocyanidins in darkness. Histological study revealed that the aleurone layers of Rdh colorless caryopses displayed bright-red after vanillin assay, but the pericarp and seed coat layers did not display color change, which indicated that the aleurone layers could accumulate precursors of polyproanthocyanidins in darkness, but the pericarp and seed coat could not. Additionally, color of Rdh caryopses changed from green in immaturity to red in maturity, and the green caryopses changed color from green to red gradually indoor for 7 days after harvest, suggesting that leucoanthocyanidins could synthesize polyproanthocyanidins. It was concluded that light was necessary for red pigment biosynthesis in red rice Rdh, leucoanthocyanidins biosyntheses in the aleurone layers did not need light, leucoanthocyanidins biosynthesis in pericarp and seed coat needed light inducing, the effect of leucoanthocyanidin biosynthesis in Rdh to light had tissue specificity.