Effects of wind and vapor pressure deficit on transpiration of tomato scions

Abstract

The effect of wind on the transpiration rate of tomato scions was studied. 1. Under high relative humidity, winds decreased the transpiration rates with increasing light intensity. Under low relative humidity, winds increased the transpiration rates. 2. Under light and high relative humidity, leaf temperature was always higher than air temperature. The difference between leaf and air temperatures decreased with air movement. 3. Irradiation with thermal rays raised leaf temperature and reversed the wind effect, thus, suppressing the transpiration rate. 4. Under light conditions, at low-VPD of air, VPD of the boundary layer was higher than VPD of air; conversely, at high-VPD of air, VPD in the boundary layer was lower. The difference of VPD between air and the boundary layer tended to be large with increasing light intensity. 5. We conclude that under high relative humidity and calm condition, the rise of leaf temperature with light increases the VPD in the boundary layer of the leaf, followed by an increase in transpiration rate. Wind, however, lowers the leaf temperature and decreases VPD in the boundary layer of the leaf, causing a decrease in the transpiration rate. 6. This result is applicable to the healing process of grafted vegetable seedlings. Under high light intensity and relative humidity, air movement hastened the healing of the grafted union, allowing the plants to grow without wilting.