Developmental Changes in the Potential for H2S Emission in Cucurbit Plants

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Abstract
Based on results obtained with leaf discs exposed to sulfate, leaves on cucurbit plants (Cucurbita pepo L. cv Small Sugar Pumpkin and Cucumis sativus cv Chipper) 1 to 2.5 weeks old have a low potential for H2S emission (less than 10 picomoles per min per cm2 leaf area) in response to sulfate, whereas discs from most of the leaves on plants 3 to 4 weeks old emit H2S at a higher rate (50 to 150 picomoles per min per cm2 leaf area). This difference is determined by the age of the plant, and is independent of the leaves' age or developmental stage. In response to l-cysteine, however, discs from leaves on cucurbit plants 1 to 2.5 weeks old emit H2S at higher rates (15 to 50 picomoles per min per cm2 leaf area) than in response to sulfate. Furthermore, the potential for H2S emission in response to l-cysteine decreases with increasing age of the individual leaf. Thus, most of the potential for H2S emission in response to l-cysteine is developed during germination and the early growth of cucurbit plants, but most of the potential for H2S emission in response to sulfate arises later in the development of the plants.