Q18 / 180 · AIIMS 2015 · Botany

The first carbon dioxide fixation product of $C_4$ plants is

  • Correct answer
    A
    oxaloacetic acid
  • B
    ribulose biphosphate
  • C
    phosphoenol pyruvate
  • D
    phosphoglyceric acid.

Solution

In $\mathrm{C}_4$ plants, initial fixation of carbon dioxide occurs in mesophyll cells. The primary acceptor of $\mathrm{CO}_2$ i.e., phosphoenol pyruvate (PEP) combines with $\mathrm{CO}_2$ in the presence of PEP carboxylase or PEPcase to form oxaloacetic acid, which is the first stable carbon dioxide fixation product in $\mathrm{C}_4$ pathway.

Hence, the correct answer is option: 'A'.

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