Talk about the mechanism of C4 plants.

Stomatal closure in a warm and dry atmosphere causes a lack of CO2 in the chlorenchyma. This problem is solved by the so-called C4 as corn or sugar cane plants. These plants having this mechanism have another enzyme fixing CO2, phosphoenolpyruvate carboxylase (PEP carboxylase) located in the leaf mesophyll. Atmospheric CO2 binds first to phosphoenolpyruvate (PEP) to produce oxaloacetate, a 4-carbon molecule in the mesophyll cells. The oxaloacetate is converted to malate (or aspartate, depending on the species), which passes from the mesophyll cells to the bundle sheath cells. Malate is then decarboxylated and CO2 enters into the Calvin cycle reacts with RUBP, where the Rubisco is present, to form the PGA. The C4 pathway occurs in the mesophyll, but the Calvin cycle occurs in the bundle sheath.