Which photosynthetic pathway do corn and sugarcane use?

Corn and sugarcane use C4 photosynthesis, a carbon-fixation pathway adapted to strong light, heat, and conditions that encourage photorespiration. The pathway is also called the Hatch–Slack pathway.

In C4 plants, carbon dioxide is first fixed in mesophyll cells by PEP carboxylase, which forms a four-carbon compound such as oxaloacetate. That compound is converted into acids including malate or aspartate and transported to bundle-sheath cells. There, carbon dioxide is released and refixed by RuBisCO through the Calvin cycle.

This two-cell arrangement concentrates carbon dioxide near RuBisCO and suppresses its oxygenase reaction. C4 plants therefore perform especially well in hot, sunny environments, although the pathway requires extra energy. Corn, sugarcane, sorghum, and many tropical grasses belong to the grass lineage in which C4 photosynthesis evolved repeatedly.

C4 is commonly confused with CAM photosynthesis. CAM plants also concentrate carbon dioxide, but they generally separate the steps by time—often opening stomata at night—rather than by location in two specialized cell types.