Question

in CAM plants why acid concentration increase at night and decrease at day time

Answer 1

It is because in CAM plants, stomata remain open at night and close during daytime to conserve water. When stomata are open during night, CO₂ is fixed by the action of PEP carboxylase to malic acid. This is called acidification. During daytime, when the stomata are closed, malic acid is converted to pyruvic acid and CO₂. This is called deacidification.