Photorespiration, caused by the oxygenase activity of RuBisCo/ Oxygenase and the ensuring glycolate salvage (C2) pathway, significantly diminishes the efficiency of photosynthesis is C3 plants. The altered pathway is called the C4 pathway and plants that use it are called C4 plants. The initial steps involve a temporary capture of CO2 in the form of HCO3, into a 4C, not 3C sugar. Plants that use the C4 pathway include maize, sorghum, sugarcane and many tropic plants. An overview of the pathways emphasizing the steps that precede RuBisCo is below.

Figure Carbon assimilation in C4 plant