Plants that produce a four-carbon compound during photosynthesis, mainly of tropical origin, including grasses and the agriculturally important crops maize, sugar cane, millet and sorghum.

Plants (e.g., maize and sorghum) whose carbon fixation products have four carbon atoms per molecule. Compared with C3 plants, C4 plants show little photosynthetic response to increased CO2 concentrations above 340 ppm but show a decrease in stomatal conductance, which results in an increase in photosynthetic water-use efficiency.

A C4 plant is one that produces oxaloacetic acid (a molecule that has four carbon atoms) as a stable intermediary in the first step in photosynthesis. Photosynthesis in C4 plants is more efficient in [..]