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

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