C₃ pathways

C₄ pathways

1.

The primary acceptor of CO₂ is RUBP – a six-carbon compound.

1.

The primary acceptor of CO₂ is phosphoenol pyruvate – a three-carbon compound.

2.

The first stable product is 3-phosphoglycerate.

2.

The first stable product is oxaloacetic acid.

3.

It occurs only in the mesophyll cells of the leaves.

3.

It occurs in the mesophyll and bundle-sheath cells of the leaves.

4.

It is a slower process of carbon fixation and photo-respiratory losses are high.

4.

It is a faster process of carbon fixation and photo-respiratory losses are low.

5.

Occurs in all the plants

5. 

Occurs only in C_{4 plants}