Describe the factors which affect the rate of transpiration.
Answers
Environmental factors that affect the rate of transpiration
Light. Plants transpire more rapidly in the light than in the dark. ...
Temperature. Plants transpire more rapidly at higher temperatures because water evaporates more rapidly as the temperature rises. ...
Humidity. ...
Wind. ...
Soil water.
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Answer:
Factors Affecting the Rate of Transpiration
Environmental factors such as intensity of light, temperature, atmospheric humidity, wind velocity, availability of soil water, etc., affect the rate of transpiration.
Explanation:
External Factors Affecting The Rate of Transpiration
Light
Light affects the rate of transpiration as it is directly involved in the opening and closing of stomata. Stomata open in light and close in darkness. Therefore, the rate of transpiration is high during the daytime and at night, only some amount of water is lost by cuticular and lenticular transpiration.
Light also affects the rate of transpiration indirectly by affecting the temperature and membrane permeability of the cell. Long duration of light and high intensity of light increases the temperature, thereby increasing the rate of transpiration. High intensity of light also increases the permeability of cell membrane, resulting into diffusion of water vapours into the atmosphere.
Temperature
The rate of transpiration increases with the increase in atmospheric temperature. This is because at higher temperature, there is more evaporation of water from the mesophyll cells and therefore, there is greater saturation of the leaf atmosphere with water vapour.
Rise in temperature increases the rate of water evaporation from the cell surface which opens the stomata and decreases the relative humidity of the atmosphere. As a result, there is rapid diffusion of water vapour from humid atmosphere inside the leaf to outer dry atmosphere.
Atmospheric humidity
The rate of transpiration depends upon the difference in vapour pressure between the internal atmosphere of the leaf and air outside the leaf. If outer air is more humid, it will reduce the diffusion of water vapour from leaf to the outer atmosphere. In other words, rate of transpiration decreases with the increase in relative humidity of atmosphere and the rate of transpiration increases by lowering atmospheric humidity.
Atmospheric pressure
Lowering of atmospheric pressure reduces the density of the environment which allows rapid diffusion of water vapour .In other words the rate of transpiration increases with the decrease in atmospheric pressure.
Wind velocity
Transpiring leaf continuously adds water vapour to the atmosphere. Air around the leaf becomes saturated and the rate of transpiration decreases. The wind removes the air of that area and is replaced by fresh air and results in the increase in the rate of transpiration.
Hence, the increase in wind velocity increases the rate of transpiration but very high wind velocity decreases the rate of transpiration because it leads to stomatal closure by lowering the temperature of transpiring surface.
Availability of soil water
The rate of transpiration depends upon the rate of absorption of soil water by roots. This is further influenced by a number of soil factors like soil water, soil particles, soil temperature, soil air etc. The rate of transpiration increases with the increase in the availability of water in the soil.