Transport In Plants Ques 25
25. Which is produced during water stress that brings stomatal closure
[1993]
(a) ethylene
(b) abscisic acid
(c) ferulic acid
(d) coumarin
Show Answer
Answer : b
Hints & Solutions
(b) During scarcity of water in the soil, stress hormone abscisic acid is produced which brings about stomatal closure. ABA inhibits the uptake of $K^{+}$by the guard cells and promotes leakage of malic acid from guard cell. This results in loss of water from guard cell due to its lower osmotic potential. Guard cell becomes flaccid leading to closure of stomatal aperture. ABA also causes stomatal closure under high concentration of $CO_2$ in the guard cells.
BETA
