Leaf conductance response of phaseolus vulgaris to ozone flux density

The effect of ozone flux density on leaf conductance to ozone in Phaseolus vulgaris was examined. The change in conductance was measured within the first two hours of fumigation for mature, fruiting 6-week-old plants of an ozone sensitive cultivar (Seafarer); for young, 14-day-old plants of the same cultivar; and for an ozone resistant cultivar (Gold Crop). Young Seafarer plants showed no change in conductance to ozone over a wide range of ozone flux densities. Gold Crop showed a decrease in conductance of −3.1 % /(mgO₃ m⁻² h⁻¹) whereas mature Seafarer plants exhibited a stronger decrease of −7.7% /(mgO₃ m⁻² h⁻¹). Diffusion porometer measurements taken on fruiting Seafarer plants in the field illustrated that a decrease in leaf diffusive conductance to water is related to visual ozone injury.