Question

Transpiration in plants will be lowest when:
A. There is high humidity in the atmosphere
B. High wind velocity
C. There is an excess of water in the soil
D. Environmental conditions are very dry

Answer 1

Hint: When there is a condition in which air is dry, it can accommodate more vapors of water. High wind velocity paves the way for newly transpired vapors.

Complete answer: Transpiration is defined as the loss of water in the form of water vapors from the aerial parts of a plant including leaves and stem. A very high amount of water is lost by transpiration.
Factors affecting transpiration are as stated below –
a. Temperature: Increase in temperature also increases transpiration. If transpiration increases in turn water absorption are also increased to overcome the water loss.
b. Humidity: Increase in humidity decreases the transpiration rate.
c. Light: Stomata are light-sensitive and open in the presence of light and transpiration rate increases in light. During night stomata close and decrease transpiration.
d. Leaf index: Greater the transpiring surface area, the rate of transpiration is also high.
e. Leaf orientation: More heating is caused by solar radiation. Therefore, if the light is directly incident on the leaf surface, transpiration or loss of water is also high.
f. Diseases: Transpiration rate is high in diseased plants as compared to healthy plants.
Transpiration rate falls with an increase in the relative humidity of the surrounding atmosphere because it is easier to transpire into dry air than humid air.
Hence, the correct answer is Option A.
Additional information:
The types of transpiration in plants are as mentioned below –
i. Cuticular transpiration
ii. Stomatal transpiration
iii. Lenticular transpiration

Note: Importance of transpiration:
1. Regulates the temperature of the plant.
2. Maintains turgor pressure inside the plant.
3. Helps create transpiration pull.
4. Regulates mineral distribution.