Stomata open when potassium ions accumulate in the guard cells and water enters by osmosis. This causes the guard cells to swell, bending apart and opening the stomatal pore. Protons being actively transported into the guard cells and carbon dioxide concentrations building up in the leaves are not directly involved in the mechanism of stomatal opening.

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Stomata Open When

Question 65

Multiple Choice

Stomata open when

A) potassium ions exit the guard cells and water enters by osmosis.
B) potassium ions accumulate in the guard cells and water enters by osmosis.
C) protons are actively transported into the guard cells.
D) carbon dioxide concentrations build up in the leaves.
E) Two of the above statements are correct.

Correct Answer: