Question

Internal source of CO2 in CAM plants is

• A. Oxaloacetic acid
• B. Malic acid
• C. RUBP
• D. PEPA

Answer 1

Answer: (A)

Oxaloacetic acid

In CAM plant, the stomata in the leaves remain shut during the day to reduce evapotranspiration, but open at night to collect CO${}_2$. This CO${}_2$ is fixed into oxaloacetate by PEP carboxylase, which is then converted to malate. The CO${}_2$ is stored as malate in vacuoles at night, and then in the daytime, it is transported to chloroplasts where it is converted back to CO${}_2$, which is then used during photosynthesis.

So, the correct option is 'Oxalo acetic acid'.