Plants that carry out crassulacean acid metabolism (cam) differ from c4 plants in that they do not contain rubisco. they do not need atp for photosynthesis. their stomata are open at night. they do not carry out the calvin cycle. they do not contain pep carboxylase.

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.