Question

Stomata generally open when guard cells are

• A. dried.
• B. turgid
• C. flaccid.
• D. none of these.

Answer 1

The correct option is B

turgid

The correct option is B.

An explanation for the Correct Option:

• Stomata are cellular structures found in the epidermal layer of leaves and needles that assist plants in exchanging carbon dioxide and water with the environment.
• When water enters the guard cells, the guard cells become turgid, and the thin outer wall is pushed outside, pulling the thicker inner wall outside, which causes the stomata to open.

The explanation for the incorrect options:

Option A:

• When the stoma loses too much water, as it does during a drought, chemical processes occur, signaling water and ions to exit the guard cells. The pair "deflates" as solutes depart the guard cells, sealing the stoma like two flat balloons.

Option C:

• When water is abundant, and the guard cells are turgid, the stomatal pores are the largest; when water is scarce, and the guard cells become flaccid, the stomatal apertures close.

Option D:

• The thick outside walls of the guard cells stretch out as the turgidity inside the guard cells rises. It exerts a strain on the inner walls of the guard cells, causing them to become crescent-shaped and stomata to open.

Therefore, the stomata open when the guard cells are turgid.