Question

Active $K^{+}-H^{+}$ exchange theory explains

• A. Ascent of sap
• B. Phloem conduction
• C. Ion absorption
• D. Stomatal movement

Answer 1

Answer: (D)

Stomatal movement

Transpiration occurs through stomata. The opening and closing of stomatal pore depends on the turgidity of guard cells. When guard cells become turgid the stomata open and when guard cells become flaccid the stomata close.

According to the most widely accepted theory of 'Active $K^{+}$−$H^{+}$ exchange' the guard cells become turgid or flaccid in response to entry and exit of potassium ions. The entry and exit of potassium ions is balanced by the entry and exit of protons to maintain electrical neutrality.