L-Tyrosine was found to be a good precursor of the betacyanin amaranthin in Amaranthus sp. Molten Fire. Administration of tyrosine to seedlings increased the pigment content by almost 100% and radioactive tyrosine was found to be incorporated in the pigment. DOPA was not as effective as tyrosine. L-Phenylalanine and a number of other phenyl derivatives without phenolic hydroxyl groups inhibited amaranthin biosynthesis. The system responsible for amaranthin biosynthesis from tyrosine or DOPA requires light, older seedlings requiring more light than younger ones.

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