Question

Why At High Atmospheric Humidity, The Rate Of Transpiration Is Low?

Answer 1

Hint:The difference between the saturation vapour pressure and the actual vapour pressure of a volume of air is used to calculate the saturation deficit. Rather than using the word vapour pressure, it is sometimes expressed in terms of absolute or relative humidity. If the relative humidity of the atmosphere is less than 100 percent, the air has a humidity deficit.

Complete step-by-step solution:
Water is transported from the roots to the leaves largely due to a variation in water potential. Water evaporates from the stomata to the atmosphere when the water potential outside the leaf is lower than near the stomatal air gap. The rate of transpiration is increased by drier surroundings and lower relative humidity outside the leaf. The rate of transpiration is influenced by humidity, temperature, wind, incident sunlight, and the size of the stomatal opening.
Relative humidity (RH) is the difference between the amount of water vapour in the air and the amount that air can contain at a given temperature. A hydrated leaf, like the environment on a wet day, would have a RH approaching 100 percent. Any decrease in atmospheric water generates a gradient that allows water to flow from the leaf to the atmosphere. The lower the relative humidity, the less wet the air is, and the stronger the pushing force for transpiration. When the relative humidity (RH) is high, the air contains more moisture, which reduces the driving force for transpiration.

Note:The rate of transpiration is inversely related to the relative humidity in the air. When the atmosphere is highly humid, the rate of transpiration is substantially decreased because the outward dispersion of water vapours through stomata follows the rule of simple diffusion. The rate of transpiration rises proportionally as the air becomes dryer.