Question

Give scientific facts both supporting and disputing this statement: In deserts with periodic monsoon rains, CAM plants are better at accumulating biomass than C4 plants. Please give specific facts and reasoning of why you support and refute this statement.

Answer 1

All plants use C3 photosynthesis, which has been supplemented in some species with Crassulcean acid metabolism (CAM) and C4 photosynthesis. These two pathways are adaptations to dry environments. CAM photosynthesis, which occurs in about 10% of plant species, fixes CO​​​2​​​​ in the dark and the resulting organic acids are deacidified during the day. Plants with CAM close their stomata during the day, which is an effective response to drought conditions and is preferentially found in desert-dwelling succulents, for example cactuses and agaves, or in arboreal plants, for example, bromeliads and orchids, that is, in dry microenvironments. CAM has low levels of primary production.

C4 photosynthesis occurs in only 5% of plant species, principally in monocotyledon sedges and grasses and in some xeric-tolerant dicotyledon families, including chenopods and euphorbs. This form of photosynthesis occurs most commonly in arid environments, especially in regions with warm-season rainfall.