Explain the factors influencing the rate of transpiration?

Explanation

The important external factors that influence the rate of transpiration are:
1. Light: Light directly increases the rate of transpiration by inducing the opening of stomata. Starch is formed in the guard cells in the presence of light. Starch gets converted into sugars which absorb water into the guard cells. Guard cells become turgid, and stoma opens, and the rate of transpiration increases. When there is no light the stomata gets closed, and the rate of transpiration decreases.
2. Temperature: When temerature increases, the atmospheric humidity decreases and rate of transpiration increases and when temperature decreases, transpiration decreases.
3. Atmospheric humidity: It is the amount of water vapour present in the atmospheric air. When the atmospheric humidity is more, the rate of transpiration is less, and when atmospheric humidity is less the rate of transpiration is more.
4. Wind velocity: Plants produce a cloud of water vapour just above the leaves which reduces the rate of transpiration. When wind velocity removes the water vapour around the plant, then the rate of transpiration increases. But a very high wind velocity tends to close the stomata, and the rate of transpiration decreases.
5. Availability of soil water: When there is less soil water, the rate of water absorption is less, and rate of transpiration is also less.