THE IMPACT OF OZONE, ISOPRENE AND PROPENE ON ANTIOXIDANT LEVELS IN 2 LEAF CLASSES OF VELVET BEAN (MUCUNA-PRURIENS L.)

Four-week-old velvet beans (Mucuna pruriens L.) were fumigated with oz one, isoprene and propene both singly and in combination (hydrocarbon + oxidant) in controlled-environment chambers for a 4 week period. Mea surements were made of total soluble protein, ascorbate, dehydroascorb ate, lipid peroxidation, and glutathione reductase activity in mature and young velvet bean leaves, Significant increases in soluble protein concentration with respect to the controls were found in plants fumig ated with propene and isoprene+ozone for young leaves, and ozone only for mature leaves. The analysis of ascorbate concentrations in young l eaves showed a significant increase in total ascorbate for propene-fum igated plants, a significant decrease in the level of the oxidized for m (dehydroascorbate) for ozone and isoprene + ozone-treated plants, an d a significant increase in the reduced form for plants fumigated with propene, propene+ozone and isoprene+ozone, The analysis of ascorbate levels in mature leaves showed no significant effect from any fumigati on regime. When compared to control material the specific activity of the enzyme glutathione reductase was found to be significantly reduced in young leaves treated with propene, isoprene+ozone and ozone alone, However, in mature leaves this effect is lost and there are no signif icant differences with respect to the control.