A C4 plant uses C4 carbon fixation, named for the 4-carbon molecule (oxaloacetate) as the first product of carbon fixation. C3 plants, on the other hand, first produce a 3-carbon molecule. C4 plants require more energy (ATP) for carbon fixation, making it more efficient in only certain environmental conditions. C4 plants can exist under conditions of drought, high temperature, and limited nitrogen/CO2. C4 plants include maize, sugar cane, millet, and sorghum. Carbon fixation is part of the light-independent reactions of photosynthesis.