<P> C plants preface the Calvin cycle with reactions that incorporate CO into one of the 4 - carbon compounds, malic acid or aspartic acid . C plants have a distinctive internal leaf anatomy . Tropical grasses, such as sugar cane and maize are C plants, but there are many broadleaf plants that are C. Overall, 7600 species of terrestrial plants use C carbon fixation, representing around 3% of all species . These plants have a carbon isotope signature of − 16 to − 10 ‰ . </P> <P> The large majority of plants are C plants . They are so - called to distinguish them from the CAM and C plants, and because the carboxylation products of the Calvin cycle are 3 - carbon compounds . They lack C dicarboxylic acid cycles, and therefore have higher carbon dioxide compensation points than CAM or C plants . C plants have a carbon isotope signature of − 24 to − 33 ‰ . </P> <P> Some bacteria use carboxysomes as carbon concentrating mechanism . </P> <P> Of the five other autotrophic pathways, two are known only in bacteria, two only in archaea, and one in both bacteria and archaea . </P>

The enzyme responsible for carbon fixation during the calvin cycle is called