[The influence of light on the turnover of the isoflavones formononetin and biochanin A in Cicer arietinum L].

The effect of different light conditions (white, red, far-red) and darkness on the accumulation of the isoflavones biochanin A and formononetin in Cicer arietinum L. were determined. The phytochrome system was shown not to stimulate the biosynthesis of these products. To differentiate between simultaneous synthesis and turnover of isoflavones, experiments using DL-phenylalanine-(I-(14)C) as precursor were performed with dark and far-red grown seedlings. The results indicate that the active phytochrome (P fr ) inhibits isoflavone synthesis, presumably at a late stage, and also prevents further turnover. In dark grown plants both synthesis and turnover were found to take place. The results are discussed on the basis of the assumption that more than one isoflavone pool may have been involved. The percent distribution of biochanin A and formononetin in different plant organs was determined and the results are discussed in relation to isoflavone metabolism.