Why photorespiratisn does not occur in C4 plant ?
In C4 plants photorespiration does not occur. This is because they have a mechanism that increases the concentration of CO2 at the enzyme site and due to the kranz anatomy. The  mesophyll cells lacks RuBisCo enzyme. The malic acid from the mesophyll is broken down in the bundle sheath cells to release CO2.This results in increasing the intracellular concentration of CO2. This ensures that the RuBis O function as a carboxylase minimising the oxygenase activity.