Plants that use crassulacean acid metabolism (CAM) photosynthesis repair CO2 at night, when their stomata are open. CAM plants stock the CO2 typically in the method of malic acid via carboxylation of phosphoenolpyruvate to oxaloacetate, which is then concentrated to malate. Decarboxylation of malate during the day discharges CO2 inside the leaves, therefore permitting carbon fixation to 3-phosphoglycerate by RuBisCO.
