In succulent plants, the stomata open in the night and close in the day. Which among the following would be the best hypothesis to explain the mechanism of stomatal action in the night only?

Question

In succulent plants, the stomata open in the night and close in the day. Which among the following would be the best hypothesis to explain the mechanism of stomatal action in the night only?, CO 2 accumulates, reduces pH, stimulate enzymes resulting in accumulation of sugars., Increases in CO 2 concentration, conversion of organic acids into starch resulting in the increased conversion into sugars resulting in K + transport., Low CO 2 concentration accumulates organic acids resulting in the increased concentration of cell sap., CO 2 used up, increase pH results in accumulation of sugars.

MARKS App · Accepted Answer

In CAM plants stomata open at night. In these plants night acidification occurs. i.e., malic acid is synthesised during night due to incomplete oxidation of carbohydrates. In night, 2 C 6 H 1 2 O 6 + 3 O 2 → 3 C 4 H 6 O 5 + 3 H 2 O malic acid ↓ leads to opening of stomata At night malic acid formed in guard cells dissociates into H + and malate ions. K + ion exchange from subsidiary cells with H + ions. Thus due to accumulation of K + ions osmotic pressure of guard cells increases, endosmosis occurs and guard cells become turgid due to which stomata opens. The malic acid at day time breaks into CO 2 and pyruvic acid thus increasing the concentration of CO 2 in mesophyll cells. This is utilised in Calvin cycle to form sugar which is finally converted into starch.

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