On the Non-protein Cysteine in Plants

Abstract

P. sativum contains non-protein cysteine in the ovules, young and ripe seed, and in the green shells of the unripe fruit; cystine is present in the leaves. From histo-chemical studies it is very probable that cysteine is widespread in the higher plants, not only in the meri-stem but also in the "reserve" tissues and in latex. By the microchemical color reaction of plant tissue with ammoniacal sodium nitroprusside, it is not only possible to detect cysteine but also to follow histochemically its oxidation in the living tissues. It is very probable that in the pea the cysteine is bound with glutaminic acid as a dipeptide such as glutathione. The presence of free cysteine and of proteins corresponding to philothion in the pea is not excluded.