Emission of ethylene and ethane by leaf tissue exposed to injurious concentrations of sulfur dioxide or bisulfite ion.

Leaf tissues injured with SO(2) gas or bisulfite ion in solution emit ethylene and ethane. The amounts of these gases produced by the tissues depend on the degree of exposure to SO(2) or bisulfite. The amount of ethylene produced in response to SO(2) fumigation correlates positively with SO(2) exposure (0 to 5.5 microliters per liter for 16 hours), SO(2) absorbed, and the amount of visible injury sustained by the leaf tissues. Ethane production is correlated positively with the injury resulting from treatment with bisulfite ion. The rate of emission of ethane from leaf discs of cucurbit cultivars as a result of exposure to bisulfite solutions is in agreement with the order and the degree of their resistance to injury by SO(2). Thus, exposure to bisulfite and the subsequent release of ethane can be used to determine the relative resistance of different species and cultivars to SO(2) gas.A rapid, simple, objective assay for SO(2) resistance based on ethane emission is described. This assay should preferentially detect SO(2) resistance which does not depend on stomatal behavior. The screening of several other cucurbits with this assay showed a 24-fold difference between the most and the least sensitive plants tested.