A) ABA theory
B) Munch theory
C) Starch glucose theory
D) Active\[{{K}^{+}}\]transport theory
Correct Answer: A
Solution :
Formation of abscisic acid (during drought or mid-day) promote reversal of\[{{H}^{+}}{{K}^{+}}\]pump and increases availability of\[{{H}^{+}}\]inside the guard cell cytoplasm and stomata close. Active\[{{K}^{+}}\]transport theory proposed by Levitt is the latest and most accepted theory for opening and closing of a stomata, according to this theory pH of guard cell increase due to active\[{{H}^{+}}\]uptake by cell and \[C{{O}_{2}}\]assimilation by guard cell. Rise in pH of guard cells causes hydrolysis of starch to form phosphoenol pyruvate. Phosphoenol pyruvate combine with \[C{{O}_{2}}\]with the help of PEPase and forms oxalic acid which gets changed into malic acid.\[{{H}^{+}}\]ions pass out of the guard cells while\[{{K}^{+}}\]ions of epidermal cells pass into the guard cells.\[{{K}^{+}}\]combine with malate. It results in absorbtion of water from adjacent cells, development of turgor and hence, opening of stomata. Starch glucose theory was proposed by Sayre. This theory is not accepted at present. Munch theory or mass flow theory proposed by Munch, is related with translocation of organic food.
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