AIIMS2008BotanyTransport in Plants
In succulent plants the stomata open in night and close in day. Which among the following would be best hypothesis to explain the mechanism of stomatal action in night only?
Options
- A( CO ₂ ) accumulates, reduces ( pH ), stimulate enzymes resulting in accumulation of sugars.
- BIncrease in ( CO ₂ ) concentration, conversion of organic acids into starch resulting in the increased convers
- CLow ( CO ₂ ) concentration accumulates organic acids resulting in the increased concentration of cell sap.
- D( CO ₂ ) used up, increase ( pH ) results in accumulation of sugars.
Correct answer
B. Increase in ( CO ₂ ) concentration, conversion of organic acids into starch resulting in the increased convers
Step-by-step solution
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 ₁₂ 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 anDguard cells become