C4 plants fix carbon dioxide into compounds containing 4 carbon atoms before entering the Calvin Cycle. These plants use the C4 carbon fixation pathway to form the 4 carbon compound, oxaloacetate, which is then converted again into aspartic acid (another 4 carbon compound), and then transferred to the bundle sheath cell; light and dark reactions of photorespiration may occur here. Aspartic acid is then broken down into carbon dioxide, which enters the Calvin Cycle, and pyruvic acid, a 3 carbon compound. C4 plants are considered highly evolved, more so than C3 plants. They are also found in very hot and dry climates. Some examples of C4 plants are grass, corn, and sugarcane. I don’ t know why all of my pictures so far are posting sideways, but hey, at least they’re posting.