Question

Primary $CO_2$ acceptor of CAM plant

• A. OAA
• B. PGA
• C. PEP and RuBP
• D. citric acid

Answer 1

Answer: (C)

PEP and RuBP

Answer 2

Primary acceptor of CAM plant is PEP and RuBP. In CAM plants stomata are open at night. $CO_2$ is absorbed from outside. With the help of PEP carboxylase it is immediately fixed. The acceptor is phosphoenol pyruvate or PEP. Malic add is end product of dark fixation of $CO_2$. It is stored inside cell vacuoles. During daytime stomata are closed. However light is available for photosynthesis. Malic acid moves out of the cell vacuoles. It is decarboxylated with the help of malic enzyme. Pyruvate is produced. It is metabolised. The released $CO_2$ is again fixed through Calvin cyde with the help of RuBP and Rubisco. CAM plants perform acidification or dark fixation of $CO_2$ during night and deacidification during day to release $CO_2$ for adual photosynthesis.