Evidence for the Repair of Ozone‐induced Membrane Injury

Abstract

The increase in [14C]‐2‐deoxy‐D‐glucose uptake by leaf discs 24 hr after fumigation was used as a measure of ozone injury to pinto bean leaves (Phaseolus vulgaris). This method showed that the primary leaves were most affected by ozone when plants were 10 to 12 days old, which coincided with the time of maximum leaf necrosis. However, 8‐day‐old plants, which had no visible leaf injury, still showed a higher uptake rate than controls, indicating that injury occurred at the cellular level. In these younger plants, uptake was shown to return to normal over a 5 day period. Moreover, the rate of this “repair” was retarded by cold or continuous darkness, enhanced by continuous light, and very markedly increased by glucose applied to the leaves. The timing of the glucose application was not critical, nor did H2O or mannitol have an effect. The results suggest that ozone injury at the cellular level can be repaired by energy‐dependent processes so that necrosis of the leaf tissue does not occur. These experiments also show that conditions and treatments after ozone exposure can alter the degree of ozone injury.