Evidence for an intracellular sulfur cycle in cucumber leaves.

H2S emission from cucumber (Cucumis sativus L.) leaf discs supplied with L-cysteine in the dark is inhibited 80-90% by aminooxyacetic acid (AOA), an inhibitor of pyridoxal-phosphate dependent enzymes. Exposure to L-cysteine in the light enhanced the emission of H2S in response to this sulfur source.