Botany - Photosynthesis in Higher Plants Question with Solution | TestHub

Crassulacean Acid Metabolism (CAM pathway) occurs in succulent plants. CO2 is fixed during the night (dark) to malic acid via PEP carboxylase. This CO2 comes from respiration (the breakdown of starch) as also from the atmosphere. Malic acid gets stored in vacuoles during the night which is decarboxylated to release during the day. Formation of malic acid during dark is called acidification or phase-I. Release of for actual photosynthesis during day is called deacidification or phase-II.

The CAM plants also contain the enzyme of Calvin cycle. Thus during day time, malic acid breaks into pyruvate and CO2. While CO2, enters the calvin cycle, pyruvate is used up to regenerate PEP. The succulents, therefore synthesize plenty of organic acids from CO2 during night (when stomata are open) and plenty of carbohydrates during the day (when stomata are closed).