Table 1.

The distribution of CCMs among extant organisms.

mechanism	location within organism	phylogenetic distribution	references
a. Passive CO2 entry, energized conversion to ${\text{HCO}}_3^{-}$	plasmalemma, thylakoid; ${\text{HCO}}_3^{-}$→CO2 and assimilation by rubisco in carboxysomes	cyanobacteria	Badger et al. (1998, 2002), Price & Badger (2003), Giordano et al. (2005) and Price et al. (2007)
b. Energized entry of ${\text{HCO}}_3^{-}$	plasmalemma, carboxysomes	cyanobacteria	Badger et al. (1998, 2002), Price & Badger (2003), Giordano et al. (2005) and Price et al. (2007)
c. Energized entry of CO2	plasmalemma? plastid envelope? rubisco in stroma/pyrenoid	many algae, and either CO2 or ${\text{HCO}}_3^{-}$ in hornworts with CCMs and some of the aquatic vascular plants with CCMs (see e and f)	Smith & Griffiths (1996), Colman et al. (2002), Maberly & Madsen (2002), Giordano et al. (2005), Raven et al. (2005b), Kevekordes et al. (2006), Burey et al. (2007), Moroney & Ynalvez (2007), Roberts et al. (2007a) and Spalding (2007)
d. Energized entry of ${\text{HCO}}_3^{-}$	plasmalemma? plastid envelope? rubisco in stroma/pyrenoid	many algae, and either CO2 or ${\text{HCO}}_3^{-}$ in hornworts with CCMs and some of the aquatic vascular plants with CCMs (see d and f)	Smith & Griffiths (1996), Colman et al. (2002), Maberly & Madsen (2002), Giordano et al. (2005), Raven et al. (2005b), Kevekordes et al. (2006), Burey et al. (2007), Moroney & Ynalvez (2007), Roberts et al. (2007a) and Spalding (2007)
e. Energized flux of H+ to cell wall, conversion of ${\text{HCO}}_3^{-}$ to CO2	plasmalemma, CO2 flux to rubisco in stroma	some algae, including characean green algae, and either CO2 or ${\text{HCO}}_3^{-}$ in hornworts with CCMs and some of the aquatic vascular plants with CCMs (see d and e)	Walker et al. (1980), Beer et al. (2002), Maberly & Madsen (2002), Helblom & Axelsson (2003), Uku et al. (2005)
f. Energized flux of H+ to thylakoid lumen, conversion of ${\text{HCO}}_3^{-}$ to CO2	thylakoids, CO2 flux to rubisco in pyrenoid	freshwater green microalga Chlamydomonas	Pronina & Semenenko (1992), Raven (1997a), Giordano et al. (2005) and Moroney & Ynalvez (2007)
g. C4 metabolism in single-cell type	inorganic C+C3 acid→C4 acid in cytosol, C4 acid→C3 acid + CO2 in chloroplast stroma (or nearby), rubisco in stroma	marine green acellular macroalga Udotea, possibly a marine diatom, a few terrestrial and submerged flowering plants	Beardall et al. (1976), Reiskind et al. (1988), Raven (1997a), Sage & Monson (1998), Reinfelder et al. (2000), Keeley & Rundel (2003), Edwards et al. (2004), Giordano et al. (2005), Osborne & Beerling (2006), Roberts et al. (2007a,b)
h. C4 metabolism in two-cell types	inorganic C+C3 acid from bundle sheath (bs) cell→C4 acid in cytosol of mesophyll (mes) cell, C4 acid→bs cell, decarboxylated to C3 acid (→mes) and CO2 fixed by rubisco in stroma of bs chloroplasts.	most C4 terrestrial flowering plants, a few amphibious/aquatic flowering plants	Sage & Monson (1998), Keeley & Rundel (2003) and Osborne & Beerling (2006)
i. C3–C4 intermediate	combinations of improved internal recycling of photorespiratory CO2 and partial two-cell C4 photosynthesis in flowering plants; in one cell in a diatom?	a few terrestrial flowering plants, and a diatom	Sage & Monson (1998) and Roberts et al. (2007a,b)
j. Crassulacean acid metabolism	inorganic C+C3 organic acid in dark in cytosol of mes→C4 acid stored for approximately 12 hours in vacuole; in light C4 acid→cytosol→C3 acid (→carbohydrate) and CO2 fixed by rubisco in stroma	some aquatic/amphibious lycophytes, a few terrestrial ferns and gymnosperms, some terrestrial and aquatic vascular plants	Winter & Smith (1995), Keeley (1998) and Keeley & Rundel (2003)