STOMATAL RESPONSES OF WHITE BEAN TO O-3 AND SO-2 SINGLY OR IN COMBINATION

The gas mixture of 0.15 ppm O3 and 0.15 ppm SO2 increased stomatal resistance of both the upper and lower primary leaf surfaces of Phaseolus vulgaris L. (cv. Sanilac) much more than did O3 or SO2 alone. The change in resistance occurred from the first day of exposure and was unrelated to the visible injury of the leaves. It is important when measuring effects on stomatal resistance that both upper and lower leaf surfaces be considered since stomatal responses vary. The difference in stomatal response does not seem to explain the differences in injury development between O3 alone and O3 and SO2 combined. © 1979.