AIIMS 2008
- Exam
- AIIMS
- Year
- 2008
- Subject
- Botany
- Chapter
- Transport in Plants
AIIMS 2008 · Botany · Transport in Plants
In succulent plants the stomata open in night and close in day....
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(\mathrm{CO}_2) accumulates, reduces (\mathrm{pH}), stimulate enzymes resulting in accumulation of sugars.
- BIncrease in (\mathrm{CO}_2) concentration, conversion of organic acids into starch resulting in the increased conversion into sugars resulting in (\mathrm{K}^{+})transport.
- CLow (\mathrm{CO}_2) concentration accumulates organic acids resulting in the increased concentration of cell sap.
- D(\mathrm{CO}_2) used up, increase (\mathrm{pH}) results in accumulation of sugars.
Correct answer
B. Increase in (\mathrm{CO}_2) concentration, conversion of organic acids into starch resulting in the increased conversion into sugars resulting in (\mathrm{K}^{+})transport.
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, (malic acid)
leads to opening of stomata At night malic acid formed in guard cells dissociates into and malate ions. ion exchange from subsidiary cells with ions. Thus due to accumulation of ions osmotic pressure of guard cells increases, endosmosis occurs anDguard cells become turgid due to which stomata opens. The malic acid at day time breaks into and pyruvic acid thus increasing the concentration of in mesophyll cells. This is utilised in Calvin cycle to form sugar which is finally converted into starch.