Editing Poaceae (section)

=== Growth and development ===
[[File:Grassflowers.jpg|upright=1.15|thumb|Grass flowers]]
Grass blades grow at the base of the blade and not from elongated stem tips. This low growth point evolved in response to grazing animals and allows grasses to be [[grazing|grazed]] or [[lawnmower|mown]] regularly without severe damage to the plant.<ref name="Attenborough-1984">{{cite book|title=The Living Planet|first=David |last=Attenborough|publisher=[[British Broadcasting Corporation]]|isbn=978-0-563-20207-3|year=1984|author-link=David Attenborough|title-link=The Living Planet }}</ref>{{rp|113–114}}

Three general classifications of growth habit present in grasses: bunch-type (also called caespitose), [[stolon]]iferous, and [[rhizome|rhizomatous]].<ref>{{Cite book|last=Staller|first=John|url=https://books.google.com/books?id=jHL1dry3W_oC&pg=PA131|title=Maize Cobs and Cultures: History of Zea mays L.|date=2009-12-02|publisher=Springer Science & Business Media|isbn=978-3-642-04506-6|language=en}}</ref>
The success of the grasses lies in part in their morphology and growth processes and in part in their physiological diversity. There are both [[C3 carbon fixation|C3]] and [[C4 carbon fixation|C4]] grasses, referring to the photosynthetic pathway for carbon fixation. The C4 grasses have a photosynthetic pathway, linked to specialized [[Kranz anatomy|Kranz leaf anatomy]], which allows for increased [[water use efficiency]], rendering them better adapted to hot, arid environments.<ref>{{Cite book|last=Gibson|first=David J.|url=https://books.google.com/books?id=QZIUDAAAQBAJ|title=Grasses and Grassland Ecology|date=2009|publisher=Oxford University Press|isbn=978-0-19-852918-7|language=en|page=63}}</ref>

The C3 grasses are referred to as "cool-season" grasses, while the C4 plants are considered "warm-season" grasses.<ref name="Cope-2009"/>{{rp|18–19}}
* Annual cool-season – [[wheat]], [[rye]], annual bluegrass (annual meadowgrass, ''[[Poa annua]]''), and [[oat]]
* Perennial cool-season – orchardgrass (cocksfoot, ''[[Dactylis glomerata]]''), fescue (''[[Festuca]]'' spp.), [[Kentucky bluegrass]] and perennial ryegrass (''[[Lolium perenne]]'')
* Annual warm-season – [[maize]], [[sudangrass]], and [[pearl millet]]
* Perennial warm-season – [[big bluestem]], [[Indiangrass]], [[Bermudagrass]] and [[switchgrass]].

Although the C4 species are all in the [[PACMAD clade]] (see diagram below), it seems that various forms of C4 have arisen some twenty or more times, in various subfamilies or genera. In the ''[[Aristida]]'' genus for example, one species (''A. longifolia'') is C3 but the approximately 300 other species are C4. As another example, the whole tribe of [[Andropogoneae]], which includes [[maize]], [[sorghum]], [[sugar cane]], "[[Job's tears]]", and [[bluestem grass]]es, is C4.<ref name="GPWGII-2012"/> Around 46 percent of grass species are C4 plants.<ref>{{Cite book|last=Harris|first=Stephen A.|url=https://books.google.com/books?id=QkedAwAAQBAJ&pg=PT28|title=Grasses|date=2014-04-15|publisher=Reaktion Books|isbn=978-1-78023-313-0|language=en}}</ref>