Question

The change in turgor pressure which cause the opening and closing of stomata is caused by

• A. Reversible starch-sugar conversions.
• B. Reversible absorption and loss of potassium ions.
• C. Loss of chloride ions.
• D. None of the above.

Answer 1

Answer: (B)

Reversible absorption and loss of potassium ions.

According to the most widely held view, the intake of potassium ions by the guard cells, reduces water potential in them, which leads to gain of water by the guard cells. The intake of water makes the guard cells turgid and they swell leading to opening of guard cells. When potassium ions move out of the guard cells, these changes are reversed.