Resistance to injury by sulfur dioxide : correlation with its reduction to, and emission of, hydrogen sulfide in Cucurbitaceae

In Cucurbitaceae young leaves are resistant to injury from acute exposure to SO(2), whereas mature leaves are sensitive. After exposure of cucumber (Cucumis sativus L.) plants to SO(2) at injurious concentrations, illuminated leaves emit volatile sulfur, which is solely H(2)S. Young leaves emit H(2)S many times more rapidly than do mature leaves. Young leaves convert approximately 10% of absorbed [(35)S]SO(2) to emitted [(35)S]H(2)S, but mature leaves convert less than 2%. These results suggest that a high capability for the reduction of SO(2) to H(2)S and emission of the H(2)S is a part of the biochemical basis of the resistance of young leaves to SO(2).