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Q.
The stomata in CAM plants open during
AMUAMU 2006
Solution:
Certain plants, especially succulents, which grow under semi-arid conditions, fix atmospheric $CO_{2}$ in dark. The process was first observed in plants belonging to family Crassulaceae and termed as crassulacean acid metabolism. In CAM plants, stomata are open at night and remain closed during most of the day. The diurnal fluctuation in acidity in CAM plants is due to change in amount of vascular malic acid in mesophyll cells. During night, malic acid is synthesized utilising, $CO_{2}$ which then accumulates in the vacuole and may account for about $85\%$ of the total titrable acid content. During day this malic acid is consumed resulting in the decrease of acidity.