Sensitivity of satsuma mandarin to ozone as related to stomatal function indicated by transpiration rate, change of stem diameter, and leaf temperature

Abstract

Transpiration rate, stem diameter, and leaf temperature of satsuma mandarin (Citrus unshiu Marc.) were found to be sensitive indicators of stomatal response to ozone exposure. Time of reaction of each to 1.2 ppm ozone was 3 min. Stem diameter showed marked oscillation and leaf temperature slight oscillation, when ozone was applied. Correlation coefficient between ozone concentration and transpiration rate at the equilibrium status after the beginning of exposure was r = 0.718, and increasing the concentration of ozone decreased stomata size. Thus, it was determined that low sensitivity of satsuma mandarin to ozone is due to rapid stomatal closure by ozone.