Question

The opening of stomata is due to the accumulation of

• A. $M{g}^{2+}$
• B. $N{a}^{+}$
• C. $K^{+}$
• D. $P$

Answer 1

Answer: (C)

Active $K^{+}$ transport mechanism was given by Fujino. According to this theory when leaf is exposed to light, malic acid appears in guard cells by hydrolysis of starch. This malic acid get dissociated into malate and $H^{+}$ ions. $H^{+}$ ions leave the guard cell and $K^{+}$ ions accumulate in guard cell. $K^{+}$ ions react with malate to form potassium malate which is osmotically active, as a result water from the adjoining cell enters the guard cells, increases its turgor pressure and the stomata opens. The extent of K+ in the guard cells determines the size of stomatal opening.