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 in the night only?

Options

A. `CO_2` accumulates, reduces pH, stimulate enzymes resulting in accumulation of sugars.
B. increse in `CO_2` concentration, conversion of orgainc acids into starch resulting in the increased conversion into sugars resulting in K* transport
C. low `CO_2`, concentration accumulates organic acids resulting in the increased concentration of cell sap.
D. `CO_2` used up, increase pH. Results in accumalation of sugars.

Answer

B

Explanation

In CAM plants stomata open at night. In these plants night acidification occurs. i.e., malic acid is synthesised during night due to incemplete oxidation of carbohydrates
`{:(2C_6H_12O_6+3O_2rarr3O_2rarr3C_4H_6O_5+3H_2O),(" ""( malic acid )"),(" "darr),(" "" 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 open. The malic acid at day time breaks into `CO_2`, and pyruvic acid thus increasing the concentration of `CO_2` in mesoplıyll cells. This is utilised in the Calvin cycle to form sugar which is finally converted into starch.