About 8,100 plant species use C4 carbon fixation, which represents about 3% of all terrestrial species of plants.[17][18] All these 8,100 species are angiosperms. C4 carbon fixation is more common in monocots compared with dicots, with 40% of monocots using the C4 pathway, compared with only 4.5% of dicots. Despite this, only three families of monocots use C4 carbon fixation compared to 15 dicot families. Of the monocot clades containing C4 plants, the grass (Poaceae) species use the C4 photosynthetic pathway most. 46% of grasses are C4 and together account for 61% of C4 species. These include the food crops maize, sugar cane, millet, and sorghum.[19][20] Of the dicot clades containing C4 species, the order Caryophyllales contains the most species. Of the families in the Caryophyllales, the Chenopodiaceae use C4 carbon fixation the most, with 550 out of 1,400 species using it. About 250 of the 1,000 species of the related Amaranthaceae also use C4.[10][21]
Members of the sedge family Cyperaceae, and members of numerous families of eudicots – including Asteraceae (the daisy family), Brassicaceae (the cabbage family), and Euphorbiaceae (the spurge family) – also use C4.