Question

Which of the following statements are true or false? Give reason in support of your answer. [5 MARKS]
(a) Potometer is an instrument used for demonstration of transpiration occurring from the lower surface of leaf.
(b) Forests contribute in bringing rains.
(c) Hydathodes are similar to stomata in plant physiology.
(d) Atmospheric humidity promotes transpiration from a green plant.
(e) Some desert plants have sunken stomata on their leaves.

Answer 1

Each Part: 1 Mark

(a) True. More transpiration occurs from the lower surface of the leaf because of the presence of more somata and potometer is attached by a leafy shoot.
(b) True. Transpiration increases the moisture in the atmosphere and brings rain.
(c) True. In addition to the stomata, many kinds of leaves have large specialised water pores in their epidermis. These pores are called hydathodes and permit guttation, the process by which a plant loses liquid water. As far as morphology and anatomy are concerned, both stomata and hydathodes are similar. But unlike the stomata, the hydathodes remain open all the time.
(d) False. High atmospheric humidity reduces the rate of outward diffusion of the internal water vapour across stomata, thereby reducing the rate of transpiration.
(e) True. Many plants and specially those which grow in a dry climate evolve a variety of permanent adaptations to curtail transpiration.