Question

During the opening and closing of stomata, when there is an influx of $K^{+}$ then there is efflux of

• A. $H^{+}$
• B. $C{l}^{-}$
• C. $K^{+}$
• D. $N{a}^{+}$

Answer 1

The correct option is A

$H^{+}$

The $K^{+}$ pump hypothesis for stomatal opening and closing was given by Levitt (1974). When stomata open, the pH of guard cells rises due to $H^{+}$ uptake by chloroplast or mitochondria. Raised $p^H$ causes hydrolysis of starch to form phosphoenolpyruvate which combines with $C{O}_2$ to form oxaloacetate. The oxaloacetate dissociates to malate and $H^{+}$.

With the help of ATP and cAMP, guard cells send out $H^{+}$ ions and absorb $K^{+}$ from adjacent epidermal cells. To counterbalance $K^{+}$, a lot of $C{I}^{-}$ are also absorbed.