Question

The correct hypothesis to explain opening of stomata during night in succulent plants is

• A. $C{O}_2$ used, pH increases and results in the accumulation of sugars.
• B. $C{O}_2$ accumulates, reduces pH and stimulates enzymes to bring about accumulation of sugars.
• C. Low $C{O}_2$ concentration, accumulation of organic acids resulting in the increased concentration of cell sap.
• D. Increases in $C{O}_2$ concentration brings conversion of organic acids into starch resulting in an increased uptake of $K^{+}$ and water.

Answer 1

The correct option is C Low $C{O}_2$ concentration, accumulation of organic acids resulting in the increased concentration of cell sap.

Scotoactive stomata are the stomata, which open in dark and close during the day time. Scotoactive stomata occur in succulents, e.g., cactus and bryophyllum. Succulents perform crassulacean acid metabolism or CAM in their photosynthesis. Nishida explained, that in succulents during night there is accumulation of organic acids, whereas, during day time the organic acids breakdown releasing carbon dioxide, which keeps stomata closed. During night, because of formation of organic acids carbon dioxide is consumed and concentration of carbon dioxide is less.