Due to low atmospheric pressure, the rate of transpiration willa)rema...
Transpiration is the loss of water from the aerial parts of the plant in the form of vapour. This process is an absolute necessity when we consider the continuous absorption of water by the roots. The additional water, which is not utilized is lost due to transpiration.
On average, nearly 98 to 99% absorbed water is lost during day time, when the stomata are open, due to transpiration. Scientists have found out that a maize plant may lose as much as 3 to 4 L of water daily in this process.
Transpiration may take place in the following ways:
A. Stomatal transpiration accounts for nearly 90 to 95% of the total transpiration, which occurs via stomata of leaves, young stem, or even fruits.
B. Lenticular transpiration (0.1%), through the lenticels of old stems.
C. Cuticular transpiration (3 to 10%), through the cuticle layer on the epidermis of some leaves.
The transpiration process is affected by the following factors:
1. Atmospheric pressure affects the rate of transpiration inversely. If the pressure increases, the rate decreases.
2. Relative humidity affects the rate of transpiration. With a decrease in RH, below 50%, the stomata close. Stomata remain open when the RH goes above 70%.
3. Temperature affects the process. An increase in temperature causes an increase in the rate of transpiration.
4. Wind affects the rate of transpiration. When a plant is suddenly exposed to a higher wind zone, the rate of transpiration increases sharply.
5. Light plays a vital role in transpiration, as it directly determines the stomatal movement.
6. Reducing soil water availability causes wilting and slowing of the rate of transpiration.