EFFECTS OF ATMOSPHERIC H2S ON THIOL COMPOSITION OF CROP PLANTS

Exposure of crop plants to H2S resulted in an increase in thiol level and a change in the composition of the thiol pool. Non-leguminous spec ies accumulated cysteine and glutathione in the light, whereas in the dark, substantial amounts of gamma-glutamyl-cysteine were also detecte d. In leguminous species, which contain homoglutathione instead of glu tathione, the level of cysteine, gamma-glutamyl-cysteine and homogluta thione increased, both in the light and in the dark. In clover, a spec ies that contains glutathione and homoglutathione, both thiols increas ed to a high level. Feeding beta-alanine to detached shoots of soybean strongly reduced the accumulation of gamma-glutamyl-cysteine. This su ggests that in legumes, the accumulation of gamma-glutamyl-cysteine up on exposure to H2S may result from a limited availability of substrate for homoglutathione synthesis.