Question

Which one is NOT correct with respect to transpiration in plants ?

• A. Transpiration is the process by which water is lost from the leaves of a plant in the form of water vapor.
• B. Transpiration is an important process for regulating the temperature of a plant by cooling the leaves through the loss of water vapor.
• C. Transpiration rates are influenced by environmental factors such as humidity, temperature, and wind speed.
• D. Transpiration plays an important and direct role in the uptake of nutrients by plants from the soil.

Hint:

Remember the distinction:
- Nutrient uptake is an active, biological process powered by root respiration and ATP.
- Transpiration is a passive, physical process driven by solar energy and water potential gradients.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
Transpiration is the physiological process of water loss from plant tissues (primarily leaves) in the form of water vapor.
It is driven by solar radiation and the vapor pressure gradient between the leaf interior and the atmosphere.

Step 2: Detailed Explanation:
Let us analyze each statement to evaluate its scientific accuracy:
Statement (A):
This is the correct definition of transpiration.
Over $95\%$ of the water absorbed by plant roots is lost to the atmosphere as water vapor, primarily through stomatal pores.
Thus, Statement (A) is correct.
Statement (B):
Transpiration provides evaporative cooling to the leaf surface.
As liquid water evaporates inside the leaf and escapes through the stomata, it absorbs latent heat, lowering leaf temperatures by up to $2 - 5\text{ }^\circ\text{C}$ below ambient air temperatures.
Thus, Statement (B) is correct.
Statement (C):
Transpiration rates are highly sensitive to environmental factors:
- High temperature increases the vapor pressure deficit, accelerating transpiration.
- High humidity decreases the deficit, slowing down transpiration.
- Wind speed removes the humid boundary layer around the leaf, accelerating transpiration.
Thus, Statement (C) is correct.
Statement (D):
This statement is incorrect.
While transpiration pull drives the mass flow of water containing dissolved minerals from the roots to the shoots, it does not play a direct role in nutrient uptake by the roots.
Nutrient uptake across root cell membranes is an active, selective biological process mediated by specific transport proteins (ion channels and carriers) that require metabolic energy (ATP).
This active uptake occurs even when transpiration rates are extremely low (such as at night or under high humidity conditions).

Step 3: Final Answer:
The statement that is not correct is: "Transpiration plays an important and direct role in the uptake of nutrients by plants from the soil."
This corresponds to Option (D).