||Arrivault S et al., Metabolite profiles reveal interspecific variation in operation of the Calvin-Benson cycle in both C4 and C3 plants. J Exp Bot. 2019 Mar 27 70(6):1843-1858. doi: 10.1093/jxb/erz051 abstract & p.1844 left column bottom paragraphPubMed ID30773587
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||Primary source Sage et al. 2011, abstract: "Using isotopic screens, phylogenetic assessments, and 45 years of physiological data, it is now possible to identify most of the evolutionary lineages expressing the C(4) photosynthetic pathway."
||Abstract: "Low atmospheric CO2 in recent geological time led to the evolution of carbon-concentrating mechanisms (CCMs) such as C4 photosynthesis in >65 terrestrial plant lineages." P.1844 left column bottom paragraph: "C4 photosynthesis evolved independently >65 times in separate lineages among the angiosperms, and C4 species currently represent ~3% of terrestrial plant species and account for 23% of total terrestrial C gain (primary sources)."