Photosynthesis in Higher Plants

Which is the first CO2 acceptor enzyme in C4 plants?

1. RuDP carboxylase
2. Phosphoric acid
3. RuBisCO
4. PEP- carboxylase

Answer

(4) PEP- carboxylase

Solution

As per NCERT, in C4 plants the primary CO2 acceptor is phosphoenol pyruvate (PEP), a 3-carbon molecule present in the mesophyll cells.

∵ The enzyme responsible for this fixation is PEP carboxylase (PEPcase), which forms the 4-carbon oxaloacetic acid (OAA).

∴ Mesophyll cells lack RuBisCO; RuBisCO (RuDP carboxylase) acts later, in the bundle sheath cells, in the Calvin cycle.

Answer: (4)