Comparison of C-3, C-4, CAM plants

	C-3	C-4	CAM
Initial CO2 fixing enzyme	ribulose 1,5 bisphosphate carboxylase/oxygenase	phosphoenolpyruvate carboxylase	phosphoenolpyruvate carboxylase
Form of C in intermediates	2 PGA (phosphoglycerate) molecules (3C)	4C molecules	4C molecules
C stored in	Starch after C-3	4-C molecules before C-3 Starch after C-3	4-C molecules in vacuoles before C-3 Starch after C-3
Plant type	all plants	grasses in warm climates	plants in hot, arid regions – succulents, cacti, agaves, some orchids, and bromeliads (im)
Location of process	Chloroplasts of all phototrophs starch-rich chloroplasts lacking grana in bundle sheath cells of C4 plants	mesophyll of Kranz-Crown/Halo plants (im, diag, im)	Chloroplasts nocturnal
Evolution	earliest, conserved	later, convergent	later, convergent
Separation from C-3	none	spatial	temporal
CO2 levels		high in bundle sheath cells
Advantages	more efficient in cool, moist environments with moderate light intensity	more efficient in warm, dry environments with high light intensity	more efficient in hot, dry environments with high light intensity