Question

Which of the following process defines the amount of turgidity of a guard cell
A) Photosynthesis
B) Excretion
C) Secretion
D) Absorption

Answer 1

Hint:- Guard cells are two cells surrounding the stoma on the leaves. The stoma opens and closes. The function of the guard cells is to regulate the opening and closing of the stoma. When a guard cell is turgid the stomata are open and when the guard cell is flaccid the stomata close.

Complete answer:-
The exchange of gases in a leaf depends on the turgidity of the guard cells. When light is available the guard cells absorb water by osmosis. This makes them swell up and turgid when the guard cells are turgid this keeps the stoma open. This enables the gaseous exchange in the leaf. When the gas exchange continues, photosynthesis continues.
When light is not available, the guard cells lose water and become flaccid thus closing the stoma and stopping the gases exchange. With no carbon dioxide, the cells cannot perform photosynthesis.
Thus, if photosynthesis is occurring normally it implies that the guard cells are turgid and if the photosynthesis is not occurring it means that the guard cells are flaccid and have lost the water. Photosynthesis in the guard cells is necessary to maintain the turgidity of the guard cells.
At daytime the guard cells remain turgid, receiving sunlight and photosynthesis occurs while at night the guard cells become flaccid, thus closing the stomata and photosynthesis stops.
Thus, the right option is A.

Note:- Stomata are openings on the surface of the leaves for gaseous exchange. Guard cells have abundant chloroplasts. There is about 10 to 15 chloroplast in a single guard cell. The guard cells are kidney or bean-shaped.