Why does RuBisCO carry out preferentially carboxylation than oxygenation in C4 plants?

1. In C₄ plants, CO₂ taken from the atmosphere is accepted by a 3-carbon compound, phosphoenolpyruvic acid in the chloroplasts of mesophyll cells. 

2. This leads to the formation of 4-carbon compound oxaloacetic acid with the help of enzyme phosphoenolpyruvate carboxylase.

3. It is converted to another 4-carbon compound called malate. 

4. Malate is transported to chloroplasts of bundle sheath cells where malate is converted to pyruvate and releases CO₄ in the cytoplasm thus increasing the concentration of CO₂ in the bundle sheath cells. 

5. Chloroplasts of bundle sheath cells contains enzymes of Calvin cycle. 

6. Thus, due to high concentration of CO₂ , RuBisCO participates in carboxylation and not in oxygenation.