Physiological and ecological studies on the oestrogenic isoflavones in subterranean clover (T. subterraneum L.). II. Effects of phosphate supply

Abstract

Two experiments with the Mt. Barker strain of subterranean clover and one with the Dwalganup strain were conducted. In each experiment, increase in phosphate supply led to increases in total dry weight production.

As phosphate deficiency became more acute in the Dwalganup strain, the leaf concentrations of two isoflavones, formononetin and genistein, increased as much as twofold; a third isoflavone, biochanin A, showed little change. In the Mt. Barker strain the concentrations of genistein and biochanin A increased about twofold with increasing severity of phosphate deficiency, while those of formononetin increased at least fourfold.

It is suggested that isoflavone formation in clover leaves increases under phosphate deficiency, and that this is associated with increased carbon substrates in the leaf cells.

The relations between isoflavone levels and oestrogenic potency are discussed. Phosphate deficiency may be indirectly related to oestrogenic potency through its influence on isoflavone levels.