Utilization of atmospheric H 2 S by plant foliar tissue: Its interaction with sulfate assimilation

Exposure of spinach cotyledons to H 2 S or sulfate resulted in a concentration and time dependent accumulation of water‐soluble non‐protein thiols. The increase in thiol content upon a combined exposure to H 2 S and sulfate was comparable to that of the sum of the increases obtained by the individual exposures. However, it never exceeded the maximal level attained upon exposure to H 2 S alone. Evidently, plants are able to utilize atmospheric H 2 S as a sulfur source, which competes with the assimilatory sulfate reduction for thiol synthesis.