Night-time leaf wetting process was analyzed in relation to micrometeorological conditions in a semi-arid cornfield and its effect was examined in the following morning with reference to the leaf-to-air humidity gradient which is a driving force in transpiration. Leaf wetness occurred due to dew formation under clear and calm night conditions which decreased canopy surface temperature to the air dew-point temperature. The amount of dew on leaves collected around sunrise (06:00) was 26.4-104.3 g m-2 · leaf area, which corresponded to 0.07-0.27 mm water. Leaf wetness remained until around 10:00 and significantly decreased leaf temperature. As a result, the leaf-to-air humidity gradient also decreased in the wetted leaf compared to the non-wetted leaf. These results suggest that night-time leaf wetting induces lower transpiration rate and may play a role in diminishing plant water stress due to excess transpirational water loss in the morning in semi-arid environments. Further studies are needed in order to demonstrate this possible effect.
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