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

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

1997

A:PS

The effect of wind on tomato shoots was measured under controlled environment conditions. Transpiration rate increased with increasing light intensity (dark, 77 and 154 æmol m-2 s-1). Under high RH (97ñ3%), air movement (1 m/s) decreased the transpiration rates, whereas under low RH (70ñ4%), air movement increased the transpiration rates. Under light and high RH, leaf temperature was always higher than air temperature. The difference between leaf and air temperatures decreased with air movement. Irradiation with thermal rays raised the leaf temperature and reversed the wind effect, suppressing the transpiration rate. Under light conditions, at a low VPD of air, the VPD of the leaf boundary layer was higher than VPD of air; conversely, at a high VPD of air, VPD in the boundary layer was lower. The difference of VPD between air and the boundary layer tended to increase with increasing light intensity (77, 154 and 246 æmol m-2 s-1). It is concluded that under high RH and calm conditions, the rise of leaf temperature with light increases the VPD in the boundary layer of the leaf, followed by an increase in the transpiration rate. Wind, however, lowers the leaf temperature and decreases the VPD in the boundary layer of the leaf, causing a decrease in the transpiration rate. This result is applicable to the healing process of grafted vegetable seedlings, since under high light intensity and RH, air movement hastened the healing of the graft union, allowing the plants to grow without wilting.

v.66(1):105-112, JAPANESE SOCIETY FOR HORTICULTURAL SCIENCE, JOURNAL OF THE

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