Question

how does temperature light intensity and wind effect transpiration

Answer 1

Atmospheric Temperature:

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A high temperature opens stomata even in darkness. Besides producing a heating effect, it lowers the relative humidity of the air and increases vapour pressure inside transpiring organ. For 10°C rise in atmospheric temperature vapour pressure inside leaves doubles while relative humidity decreases by 50%. Consequently, rate of transpiration increases.

However, leaf temperature does not rise corresponding to rise in atmospheric temperature due to cooling effect of transpiration. Very high temperature may cause desiccation and closure of stomata. Very low temperature also closes the stomata and hence decreases the rate of transpiration.

Factor # 3. Light:

In the majority of plants stomata open in the presence of light and close in darkness. A strong light further increases transpiration probably due to its heating effect. Because most of the transpiration occurs through stomata, the rate of transpiration is quite high in light. It falls down appreciably in the darkness.

Factor # 4. Air Movements (Wind):

Transpiration is lower in the still air because water vapours accumulate around the transpiring organs and reduce the DPD of the air.

The movement of the air increases the rate of transpiration by removing the saturated air around the leaves. Up to 20-30 km/hr the rate of transpiration increases with the wind velocity. A wind velocity of 40-50 km/hr decreases transpiration by closing the stomata due to mechanical effect, drying and cooling of the transpiring organs.

Answer 2

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