EFFECTS OF REACTIVE HYDROCARBONS AND HYDROGEN-PEROXIDE ON ANTIOXIDANTACTIVITY IN CHERRY LEAVES

One-year-old cherry trees were fumigated with propene and gas-phase hy drogen peroxide, singly and in combination, in controlled-environment chambers for an 8-week period during the summer season. A UV light sou rce was included with the combined propene and hydrogen peroxide regim e to provide a source of hydroxyl radicals and ozone, and thus all the constituents of a photochemical smog. Measurements were made of solub le protein concentration and of glutathione reductase activity in leaf extracts from two or three leaf classes in plants from each treatment regime at the end of each fumigation period. Significant increases in soluble protein concentration with respect to the controls were found in plants fumigated with propene and hydrogen peroxide. The occurrenc e and extent of these differences depended on the leaf class and on th e timing of the fumigation period over the summer with respect to bud break. The activity of glutathione reductase was found to be significa ntly increased in mature lower leaves of plants which had been fumigat ed with hydrogen peroxide. This effect was independent of the timing o f fumigation with respect to bud break. Enzyme activity was also incre ased in propene and in propene plus hydrogen peroxide treatments, but only when plants were fumigated early in the growth season.