Study on Flavonoids in the Caryopsis of Indica Rice Rdh

To detect if there are phenolic flavonoids such as proanthocyanidins in Rdh, histochemistry assay toluidine blue O (TBO) staining and vanillin tests were performed. Rdh caryopsis transverse sections were stained by metachromatic stain TBO. It showed that there were a great deal of polyphenols in the pericarp and seed-coat tissues, and a little of them was in the cell wall of aleurone layers. The ovaries of Rdh and colorless rice were dealt with vanillin. It showed that all fertilized ovaries of Rdh were bright red regardless what degree the caryopsis maturity was, and all the ovaries of it before fertilization were not red after vanillin treatment. It suggested that every Rdh caryopsis had proanthocyanidins or its precursors, and fertilization was the premise of proanthocyanidins or its precursor synthesis. But colorless rice could not accumulate proanthocyanidins or its precursors. The pericarp, seed-coat and aleurone layer tissues of Rdh and colorless rice were anatomized and were dealt with vanillin. It was showed that three layers of Rdh were all bright red after treatment, revealing that they all had proanthocyanidins or its precursors, but colorless rice could not. It was suggested that polymerized proanthocyanindins were synthesized and accumulated in the pericarp of Rdh, and monomer-proanthocyanidins or leucoanthocyanidins were synthesized and accumulated in the seed-coat and the aleurone layer tissues.