“…Different types of CAM have been described (Messerschmid et al ., 2021; Winter and Smith, 2022), for instance, in obligate CAM plants, like most cacti, carbon is fixed constitutively at night in contrast to facultative CAM plants, where nocturnal fixation is induced by drought, salt stress or ontogeny (Winter K., 2019; Schiller and Bräutigam, 2021). In CAM cycling plants, carbon is fixed nocturnally from recycled respiratory CO 2 , and during the day with C3 photosynthesis (Schiller and Bräutigam, 2021). CAM idling plants also perform CAM cycling, but stomata are always closed (Sipes and Ting, 1985).…”