THE EFFECTS OF LOW CONCENTRATIONS OF SULPHUR DIOXIDE ON STOMATAL BEHAVIOUR IN VICIA FABA

Abstract

The stomatal resistance of leaves of Vicia faba L., measured using a diffusion porometer, rapidly decreased when plants were exposed to air containing SO2. The stomatal resistance decreased by 20% for the SO2 concentrations used (140, 290 and 1430 μg m‐3) and the minimum concentration to which stomata responded was 72 μg m‐3. Although stomatal resistance increased with leaf age, when exposed to 290 μg‐3 SO2, the opening response was larger and more rapid in the older leaves. Exposure to 290 μg m‐3 SO2 throughout a day suppressed the normal diurnal variation in stomatal behaviour and reduced the stomatal resistance by 25%. It was estimated that the measured stomatal responses to SO2 would increase the transpiration rate by 32% for single leaves in a growth room and by 23% for a field crop. Copyright © 1973, Wiley Blackwell. All rights reserved