Question

Which of the following would tend to increase transpiration?

(A) spiny leaves

(B) sunken stomata

(C) a thicker cuticle

(D) higherstomatal density.

Short answer

(A) The option “spiny leaves” is false.

(B) The option “sunken stomata” is false.

(C) The option “a thicker cuticle” is false.

(D) The option “higher stomatal density” is true.

Step-by-step solution

Transpiration

Transpiration is the process through which water moves through the plants, and excess water is eliminated via the aerial parts. This is because excess water is taken up by the roots that have no role to play. Only minimal water is necessary for metabolic processes.

Explanation of option ‘(A)’

Spiny leaves do not increase the rate of transpiration in plants. Instead, these spiny leaves lower the transpiration rate. These spines possess thick cuticles and reduced surface area, and hence the rate of transpiration reduces significantly.

Thus, spiny leaves do not increase transpiration.

Therefore, the given option is false.

Explanation of option ‘(B)’

Sunken stomata do not increase the rate of transpiration in plants. Instead, sunken stomata reduce the boundary of leaves;hence, they significantly reduce transpiration rate.

Thus, sunken stomata do not increase transpiration.

Therefore, the given option is false.

Explanation of option ‘(C)’

When leaves have a thick cuticle, the transpiration rate does not increase. The transpiration rate significantly reduces in such plants. Thick leaves are hydrophobic, and hence they lower water loss from the aerial parts of the plant.

Thus, a thick cuticle does not increase transpiration.

Therefore, the given option is false.

Explanation of option ‘(D)’

The transpiration rate of a plant greatly depends on the stomatal density. When the stomatal levels rise in the leaves, the transpiration rate gradually increases. The increase in the stomatal cells occurs when the cells of the epidermis divide and produce stomatal cells.

Thus, higher stomatal density increases the rate of transpiration.

Therefore, the given option is true.