List of C4 plants



In botany, carbon fixation is one of three known methods of photosynthesis used by plants. plants increase their photosynthetic efficiency by reducing or suppressing photorespiration, which mainly occurs under low atmospheric concentration, high light, high temperature, drought, and salinity. There are roughly 8,100 known species, which belong to at least 61 distinct evolutionary lineages in 19 families (as per APG IV classification ) of flowering plants. Among these are important crops such as maize, sorghum and sugarcane, but also weeds and invasive plants. Although only 3% of flowering plant species use carbon fixation, they account for 23% of global primary production. The repeated, convergent evolution from C3 carbon fixation ancestors has spurred hopes to bio-engineer the  pathway into  crops such as rice.

photosynthesis probably first evolved 30–35 million years ago in the Oligocene, and further origins occurred since, most of them in the last 15 million years. plants are mainly found in tropical and warm-temperate regions, predominantly in open grasslands where they are often dominant. While most are graminoids, other growth forms such as forbs, vines, shrubs, and even some trees and aquatic plants are also known among plants.

plants are usually identified by their higher 13C/12C isotopic ratio compared to plants or their typical leaf anatomy. The distribution of lineages among plants has been determined through phylogenetics and was considered well known. Monocots – mainly grasses (Poaceae) and sedges (Cyperaceae) – account for around 80% of species, but they are also found in the eudicots. Moreover, almost all plants are herbaceus, with the notable exception of some woody species from the Euphorbia genus, such as the tree Euphorbia olowaluana. The reason behind metabolism extreme rarity in trees is debated: hypotheses vary from a possible reduction in photosynthetic quantum yield under dense canopy conditions, coupled with an increased metabolic energy consumption (inherent to  metabolism itself), to less efficient sunflecks utilization.

The following list presents known lineages by family, based on the overview by Sage (2016). They correspond to single species or clades thought to have acquired the pathway independently. In some lineages that also include and – intermediate species, the  pathway may have evolved more than once.



Acanthaceae
The large acanthus family Acanthaceae includes one genus with species, found in dry habitats from Africa to Asia.


 * Blepharis – 15 species, 1–4 origins

Aizoaceae
While many species in the ice plant family Aizoaceae use crassulacean acid metabolism (CAM), one subfamily with drought-tolerant and halophytic plants includes species:


 * Sesuvioideae – 30 species, 1–6 origins

Amaranthaceae
The amaranth family Amaranthaceae (including the former goosefoot family Chenopodiaceae) contains around 800 known species, which belong to 14 distinct lineages in seven subfamilies. This makes Amaranthaceae the family with most species and lineages among the eudicots. Suaeda aralocaspica and species of the genus Bienertia use a particular, single-cell type of carbon fixation.


 * Aerva (Amaranthoideae) – 4 species
 * Alternanthera (Gomphrenoideae) – 17 species (also includes – intermediates)
 * Amaranthus (Amaranthoideae) – 90 species
 * Atriplex (Chenopodioideae) – around 180 species
 * Bassia–Camphorosma clade (Camphorosmoideae) – 24 species (also includes one – intermediate), 1–2 origins
 * Bienertia (Suaedoideae) – 3 species
 * Caroxyleae (syn. Caroxyloneae, Salsoloideae) – 157 species
 * Gomphrenoids (Gomphrenoideae) – 138 species
 * Salsoleae (Salsoloideae) – 158 species, 2–4 origins
 * Suaeda aralocaspica (Suaedoideae)
 * Suaeda sect. Salsina – 30 species
 * Suaeda sect. Schoberia – 9 species
 * Tecticornia – (Salicornioideae) 2 species
 * Tidestromia (Gomphrenoideae) – 8 species

Asteraceae
The composite family Asteraceae contains three lineages, in two different tribes of subfamily Asteroideae. They include the model genus Flaveria with closely related, , and intermediate species.


 * Flaveria (Tageteae) – 7 species, 2–3 origins  (also includes  and intermediate)
 * Coreopsideae – 41 species
 * Pectis (Tageteae) – 90 species

Boraginaceae
The borage family Boraginaceae contains one widespread genus, Euploca, which has also been treated as part of a distinct family Heliotropiaceae.


 * Euploca (also includes – intermediates ) – 130 species, 1–3 origins

Cleomaceae
The Cleomaceae, formerly included in the caper family Capparaceae, contains three species in genus Cleome. These three species independently acquired the pathway; the genus also contains numerous  as well as – intermediate species.


 * Cleome angustifolia
 * C. gynandra
 * C. oxalidea

Caryophyllaceae
In the carnation family Caryophyllaceae, the pathway evolved once, in a clade within the polyphyletic genus Polycarpaea.


 * Polycarpaea – 20 species

Cyperaceae
The sedge family Cyperaceae is second only to the grasses in number of species. Prominent sedges include culturally important species such as papyrus (Cyperus papyrus) and chufa (C. esculentus) but also purple nutsedge (C. rotundus), one of the world's major weeds. Eleocharis vivipara uses carbon fixation in underwater leaves and  carbon fixation in aerial leaves.


 * Bulbostylis – 211 species
 * Cyperus – 757 species
 * Eleocharis ser. Tenuissimae – 10 species
 * Eleocharis vivipara
 * Fimbristylis – 303 species
 * Rhynchospora – 40 species

Euphorbiaceae
The spurge family Euphorbiaceae contains the largest single lineage among eudicots. The spurges are diverse and widespread; they range from weedy herbs to the only known  trees – four species from Hawaii, including Euphorbia olowaluana (up to 10 m) and E. herbstii (up to 8 m).


 * Euphorbia subgenus Chamaesyce section Anisophyllum (also treated as genus Chamaesyce) – 350 species (also including  and – intermediate species)

Gisekiaceae
Contains a genus with a single species.


 * Gisekia pharnaceoides

Hydrocharitaceae
Includes the only known aquatic plants.


 * Egeria densa
 * Hydrilla verticillata

Molluginaceae
The two species within the same genus have acquired the pathway independently.


 * Mollugo – 2 species, 2 origins

Nyctaginaceae

 * Allionia – 2 species
 * Boerhavia – 42 species

Polygonaceae

 * Calligonum – 80 species

Portulacaceae
The single genus of this family forms one lineage. CAM photosynthesis is also known. Common purslane (Portulaca oleracea) is a major weed but also a vegetable.
 * Portulaca – 100 species, 1–2 origins

Poaceae
The grass family includes most of the known species – around 5000. They are only found in subfamilies of the PACMAD clade. Major crops such as maize, sugarcane, sorghum and pearl millet belong in this family. The only known species with, and intermediate variants, Alloteropsis semialata, is a grass.


 * Aristida – 288 species
 * Stipagrostis – 56 species
 * Chloridoideae (without Centropodieae) – 1596 species
 * Centropodia – 4 species
 * Eriachne – 50 species
 * Tristachyideae – 87 species
 * Andropogoneae – 1228 species (incl. maize, sugarcane, sorghum)
 * Reynaudia filiformis
 * Axonopus – 90 species
 * Paspalum – 379 species
 * Anthaenantia – 4 species
 * Arthropoginae/Mesosetum clade – 35 species, 1–2 origins
 * Arthropoginae/Onchorachis clade – 2 species
 * Arthropoginae/Colaeteania clade – 7 species, 1–2 origins
 * Anthephorinae – 286 species
 * Echinochloa – 35 species
 * Neurachne–Paraneurachne – 2 species, 2 origins
 * Melinidinae–Panicinae–Cenchrinae – 889 species
 * Alloteropsis – 5 species, 1–2 origins (incl.  and intermediate)

Scrophulariaceae

 * Anticharis – 4 species

Zygophyllaceae

 * Tribuloideae – 37 species, 1–2 origins
 * Tetraena simplex