Question

Opening of stomata is not affected by
(A) Calcium
(B) ${K^ + }$
(C) Starch
(D) None of the above

Answer 1

Hint: Stomata is the minute pores that is present in the leaves and stems of the plants which undergo transpiration in which the water is lost through it. This is also called the stomata apparatus which helps in the water and gaseous exchange.

Complete answer:
Guard cells are the surrounding cells of the stomata that are bean shaped and have the potassium ions in it. But in the case of grasses it is dumb- bell shaped. The pore space formed within these cells is called stomata. Transpiration is the process by which the water is lost through the stomatal openings. The process of stomata opening and the closing is controlled by the guard cells which surrounds stomata pores.

(1) Opening of stomata:
This potassium (${K^ + }$) ions maintains the reduction of the water potential and makes the cell undergo endosmosis. This process helps in the bulging of the guard cells and hence the stomata gets open. Guard cells are full of potassium ions and in order to balance it, water from the nearby guard cells enters into these guard cells. As the water enters, the guard cell becomes bulge and swollen. This process is called endosmosis. Hence, the turgor pressure gets increased causing the stoma open.

(2) Closing of stomata:
After the opening process, the potassium ions get decreased by the formation of the anions by the starch, this helps in balancing the potassium cations. Hence, the water potential increases all the water moves out of the guard cell, this makes the stomata close. This process at a time when the water from the guard cell goes out and so that the turgor pressure reduces. Hence, the pores of the stomata close. But the calcium does not have any role in the opening and the closing of the stomatal apparatus.

Hence, the correct answer is Option (A)

Note: Opening process is done at the daytime with enough sunlight and when the photosynthesis happens. And the closing of the stomata is the opposite of the opening phenomenon. And the closing occurs at the time of night where there is absence of sunlight.