Effects of O3 on the stomatal behaviour of Egyptian varieties of radish (Raphanus sativus L. cv. Baladey) and turnip (Brassica rapa L. cv. Sultani)

Abstract

The effects of O2 (80 nl 1−1) on the photosynthetic rate (A) and stormatal conductance (g) of Egyptian varieties of radish (Raphanus sativus L. ev. Baladey) and turnip (Brassica rapa L. ev. Sultani) were examined. Exposure to O3decreased A in both species, while gs was increased in radish and decreased in turnip. The effect of different concentrations of O3, (50, 100, 150 nl l−1 on radish was examined and it was found that A decreased, while g, increased, with increasing concentrations of O3. Scanning electron microscopy (SEM) of fumigated leaves showed that the increase in gs in radish resulted from the collapse of epidermal cells. Counts of the percentage of stomata which were fully open demonstrated that 80 nl 1−1 O3 caused an increase of 18% in radish and a decrease of 14% in turnip. The proportion of opened stomata was found to increase with increasing O3 concentration in radish. Copyright © 1994, Wiley Blackwell. All rights reserved