The evolution of C 4 photosynthesis

Summary C 4 photosynthesis is a series of anatomical and biochemical modifications that concentrate CO 2 around the carboxylating enzyme Rubisco, thereby increasing photosynthetic efficiency in conditions promoting high rates of photorespiration. The C 4 pathway independently evolved over 45 times in 19 families of angiosperms, and thus represents one of the most convergent of evolutionary phenomena. Most origins of C 4 photosynthesis occurred in the dicots, with at least 30 lineages. C 4 photosynthesis first arose in grasses, probably during the Oligocene epoch (24–35 million yr ago). The earliest C 4 dicots are likely members of the Chenopodiaceae dating back 15–21 million yr; however, most C 4 dicot…