Question

In CAM plants, $C{O}_2$ acceptor is

• A. RuBP
• B. PEP
• C. OAA
• D. PGA

Answer 1

The correct option is B PEP

Crassulacean Acid Metabolism (CAM) is a specialised photosynthetic process which is characterized by the following criteria given by Osmond (1978) and Cluge and Tuge (1978). These are:

1. CO${}_2$ uptake takes place mainly at night
2. stomata are open during the night and closed during the day when CO${}_2$ uptake is mostly negligible.
3. Malate accumulates at night by carboxylation of PEP.
4. Decarboxylation of malate during the day yields CO${}_2$ which is fixed up by RuBP carboxylase.

During the night time when the stomata are open, the CO${}_2$ is absorbed and fixed by phosphoenol pyruvic acid (PEP, 3C) in presence of enzyme PEP carboxylase. As a result of this PEP gets converted into oxaloacetic acid (OAA, 4C).

So the correct option is 'PEP'