Question

In $C_4$ plants, synthesis of sugars/final $C{O}_2$ fixation occurs in

• A. Palisade cells
• B. Spongy cells
• C. Undifferentiated mesophyll cells
• D. Bundle sheath cells

Answer 1

The correct option is D Bundle sheath cells

In C${}_4$ plants

1. CO${}_2$ is taken from the atmosphere is accepted by PEP present in the chloroplasts of mesophyll cells of the leaves.
   
2. It forms a first stable 4-carbon compound oxaloacetic acid.
3. This again converts into malic acid which enters into the chloroplasts of bundle sheath cells where oxidative decarboxylation occurs to form pyruvic acid.
4. CO${}_2$ released in bundle sheath cells react with Ribulose-1,5-biphosphate (RuBP) and Calvin cycle starts which fix CO${}_2$ and gives sugar.
5. Pyruvic acid again enters mesophyll cells to regenerates phosphoenol pyruvic acid.

So the correct option is 'Bundle sheath cells'.