7,617
edits
Changes
From Gardenology.org - Plant Encyclopedia and Gardening Wiki
Jump to navigationJump to searchno edit summary
{{Taxobox
| color = lightgreen
| name = Poaceae (true grasses)
| image = Meadow_Foxtail.jpg
| image_width = 240px
| image_caption = Flowering head of Meadow Foxtail (''[[Alopecurus pratensis]]''), with stamens exserted at anthesis
| regnum = [[Plant]]ae
| divisio = [[Flowering plant|Magnoliophyta]]
| classis = [[Liliopsida]]
| ordo = [[Poales]]
| familia = '''Poaceae'''
| familia_authority = ([[Robert Brown (botanist)|R.Br.]]) [[John Hendley Barnhart|Barnhart]]
| subdivision_ranks = Subfamilies
| subdivision =
There are 7 subfamilies:<br>
Subfamily [[Arundinoideae]]<br>
Subfamily [[Bambusoideae]]<br>
Subfamily [[Centothecoideae]]<br>
Subfamily [[Chloridoideae]]<br>
Subfamily [[Panicoideae]]<br>
Subfamily [[Pooideae]]<br>
Subfamily [[Stipoideae]]<br>
}}
The family '''Poaceae''', in the Class [[Liliopsida]] of the [[Magnoliophyta|flowering plants]], is also known as '''Gramineae'''. Plants of this family are usually called '''[[grass]]es'''. There are about 600 [[genus|genera]] and between 9,000-10,000 [[species]] of grasses (Kew Index of World Grass Species). Plant communities dominated by Poaceae are called [[grassland]]s; it is estimated that grasslands comprise 20% of the vegetation cover of the earth. This family is the most important of all plant families to human economies: it includes the staple [[food]] grains grown around the world, lawn and forage grasses, and [[bamboo]], widely used for construction throughout [[Asia]].
The term "grass" is also applied to many [[Grass#Other plants called grass|grass-like plants not in the Poaceae]], leading to plants of the Poaceae often being called "true grasses".
== Structure and growth ==
Grasses generally have the following characteristics (it is advisable to have a look at the image gallery for reference):
;General aspects
[[Image:Grass-plant-structure.png|250px|thumb|left|Structure of a grass plant.]]
Poaceae have hollow [[Plant stem|stems]] called '''''[[culm]]s''''', plugged at intervals called '''''nodes'''''. [[Leaf|Leaves]] are alternate, ''distichous'' (in one plane) or rarely spiral, parallel-veined and arise at the nodes. Each leaf is differentiated into a lower '''''sheath''''' hugging the stem for a distance and a '''''blade''''' with margin usually entire. The leaf blades of many grasses are hardened with [[silica]] [[phytolith]]s, which helps discourage grazing animals. In some grasses (such as [[sword grass]]) this makes the grass blades sharp enough to cut human skin. A membranous appendage or fringe of hairs, called the '''''[[ligule]]''''', lies at the junction between sheath and blade, preventing water or insects to penetrate into the sheath.
Grass blades grow at the base of the blade and not from growing tips. This location of the grass growing point near the ground allows it to be [[grazing|grazed]] regularly without damage to the growing point.
;Reproduction
[[Image:En_Anatomia.png|Parts of a spikelet|thumb|300px|left]]
[[Flower]]s of Poaceae are peculiar. They are typically arranged in a terminal '''''[[Raceme|panicle or spike]]''''' made of many small '''''spikelets''''', each spikelet having one or more florets (flowers). The florets are usually hermaphroditic ([[maize]], monoecious, is an exception) and [[pollination]] is always [[anemophily|anemophilous]]. The [[perianth]] is reduced. Each spikelet is protected by two (usually) [[bract]]s called '''''glumes''''' and each single floret is surrounded by two bracts called the '''''lemma''''' (the external one) and the '''''palea''''' (the internal). This complex structure can be seen in the image on the left, portraying a [[wheat]] (''Triticum aestivum'') spike.
The [[fruit]] of Poaceae is a ''[[caryopsis]]''.
Grass plants also spread out from a parent plant. [[Plant habit|Growth habit]] describes the type of shoot growth present in particular grass plants and is directly related to their ability to spread out from the parent plant and ultimately form a [[clonal colony]]. There are three general classifications of growth habit present in grasses; bunch-type, [[stolon]]iferous, and [[
rhizome|rhizomatous]].
The success of the grasses lies in part in their morphology and growth processes, and in part in their physiological diversity. The grasses divide into two physiological groups, using the [[C3 carbon fixation|C3]] and [[C4 carbon fixation|C4]] photosynthetic pathways for carbon fixation. The C4 grasses have a photosynthetic pathway linked to specialised [[C4 carbon fixation#C4 Leaf Anatomy|Kranz]] leaf anatomy that particularly adapts them to hot climates and an atmosphere low in [[carbon dioxide]].
==Grass evolution==
Until recently grasses were thought to have evolved around 55 million years ago, based on fossil records. However, recent findings of 65-million-year-old [[phytolith]]s resembling grass phytoliths (including ancestors of [[rice]] and [[bamboo]]) in [[Cretaceous]] [[dinosaur]] [[coprolite]]s<ref>{{cite web |url=http://www.sciencemag.org/cgi/content/summary/310/5751/1126 |title=Dinosaurs Dined on Grass |publisher=Science Magazine |author=Dolores R. Piperno and Hans-Dieter Sues |date=18 November 2005 |accessdate=2007-03-23}}</ref>, may place the diversification of grasses to an earlier date.
The [[flower]]s of grass are reduced from the general [[monocotyledon]] type. The immediate ancestor of the first grass may have been a small Liliaceous plant with rhizomes and many small flowers, growing in dense patches, which adopted [[wind]] pollination to escape limitations caused by shortage of [[insect]]s to [[pollinate]] the flowers.
==Cultivation and uses==
Agricultural grasses grown for their edible seeds are called ''[[cereal]]s''. Cereals constitute the major source of [[carbohydrate]] for humans and perhaps the major source of protein, and include [[rice]] in southern and eastern Asia, [[maize]] in [[Central America|Central]] and [[South America]], and [[wheat]] and [[barley]] in [[Europe]], northern Asia and the [[Americas]]. Some other grasses are of major importance for foliage production. [[Sugarcane]] is the major source of [[sugar]] production. Many other grasses are grown for [[forage]] and [[fodder]] for [[animal]] food, particularly for [[sheep]] and [[cattle]].
Grasses are used for construction; larger [[bamboo]]s and ''[[Arundo donax]]'' have stout culms that can be used in a manner similar to timber, and grass roots stabilize the sod of [[sod house]]s. ''Arundo'' is used to make reeds for [[woodwind instrument]]s, and bamboo is used for innumerable implements.
Grass [[fiber|fibre]] can be used for making [[paper]], and for [[biofuel]] production. Grasses are the primary plant used in [[lawn]]s, which themselves derive from grazed [[grassland]]s in Europe. ''[[Phragmites|''Phragmites australis'']]'' (common reed) is important in water treatment, wetland habitat preservation and land reclamation in the [[Old World]].
Grasses are used as food plants by many species of [[butterflies]] and [[moths]]. see [[List of Lepidoptera which feed on grasses]].
===Economically important grasses===
{|
|- valign=top
|
;[[Grain|Grain crops]]
*[[Barley]]
*[[Maize]] (Corn)
*[[Oats]]
*[[Rice]]
*[[Rye]]
*[[Sorghum]]
*[[Wheat]]
*[[Millet]]
|
;Leaf and stem crops
*[[Bamboo]]
*[[Marram grass]]
*[[Poa|Meadow-grass]]
*[[Phragmites|Reed]]
*[[Ryegrass]]
*[[Sugarcane]]
|
;[[Lawn|Lawn grasses]]
*[[Bahia grass]]
*[[Agrostis|Bent grass]]
*[[Cynodon|Bermuda grass]]
*[[Festuca|Fescue]]
*[[Poa|Meadow-grass]]
*[[Ryegrass]]
*[[Zoysia]]
|
;[[Model organism]]s
*''[[Brachypodium distachyon]]''
*[[Maize]] (Corn)
*[[Rice]]
*[[Sorghum]]
*[[Wheat]]
|}
==Grass and society==
[[Image:Grass covered house in Iceland 1972.jpg|thumb|Grass covered house in Iceland]]
Grass has long had significance in human society. It has been cultivated as a food source for [[domesticated animals]] for up to 10,000 years, and has been used to make [[paper]] since at least as early as [[2400 B.C.]]
Some [[idiom]]s evoke images of grass. For example:
*"The grass is always greener on the oth
er side" suggests that the greenness of grass is a positive quality.
*"Don't let the grass grow under your feet" references the speed with which grass grows.
*"A [[snake]] in the grass" cautions about the dangers that may be hidden in the grass.
*"When [[elephants]] fight, it is the grass who suffers" personifies the grass.
==Image gallery==
<gallery>
Image:Ruwbeemdgras_Poa_trivialis_ligula.jpg|Leaves of ''Poa trivialis'' showing the ligules
Image:Bamboo_DSCN2465.jpg|Bamboo stem and leaves, nodes are evident
Image:En_Spica_spiculae.png|Wheat spike and spikelet
Image:En_Aperta.png|Spikelet opened to show caryopsis
Image:Harestail grass.jpg|Harestail Grass
Image:Gras.jpg|Grass
Image:Saccharum-officinarum2.JPG|Sugarcane (''Saccharum officinarum'')
Image:Bromus_hordeaceus_unten.jpeg|Roots of ''Bromus hordeaceus''
Image:Ohra.jpg|Barley mature spikes (''Hordeum vulgare'')
Image:Koeh-283.jpg|Illustration depicting both staminate and pistillate flowers of maize (''Zea mays'')
</gallery>
== See also ==
* [[agrostology]]
* [[grass]]
* [[Cyperaceae|sedges]]
==References==
{{reflist}}
== External links and references ==
* [http://www.turffiles.ncsu.edu TurfFiles] by [[North Carolina State University]]
* [http://www.rbgkew.org.uk/data/grasses-db/sppindex.htm Kew Index of World Grass Species]
* [http://forages.oregonstate.edu/projects/regrowth/main.cfm?PageID=11 Definitions of Grass structures]
* [http://delta-intkey.com/angio/www/graminea.htm Poaceae] in L. Watson and M. J. Dallwitz] (1992 onwards), [http://delta-intkey.com/angio/ The families of flowering plants.]
Chapman, G.P. and W.E. Peat. 1992. An Introduction to the Grasses. CAB International, Wallingford.
Cheplick, G.P. 1998. Population Biology of Grasses. Cambridge Univ. Press, Cambridge.
* L. Watson and M. J. Dallwitz (1992 onwards). [http://delta-intkey.com/grass/ The grass genera of the world.]
*Piperno, D. R. & Sues, H.-D. (2005). Paleontology: Dinosaurs Dined on Grass. ''Science'' 310 (5751): 1126-1128 (18 November 2005) [http://www.sciencemag.org/cgi/content/summary/310/5751/1126 summary].
* [http://utc.usu.edu/keys/default.htm Interactive Keys to North American Grasses at Utah State University]
[[Category:Poales| Poaceae]]
[[Category:Plant families]]
[[Category:Grasses]]
[[Category: gardening]]
| color = lightgreen
| name = Poaceae (true grasses)
| image = Meadow_Foxtail.jpg
| image_width = 240px
| image_caption = Flowering head of Meadow Foxtail (''[[Alopecurus pratensis]]''), with stamens exserted at anthesis
| regnum = [[Plant]]ae
| divisio = [[Flowering plant|Magnoliophyta]]
| classis = [[Liliopsida]]
| ordo = [[Poales]]
| familia = '''Poaceae'''
| familia_authority = ([[Robert Brown (botanist)|R.Br.]]) [[John Hendley Barnhart|Barnhart]]
| subdivision_ranks = Subfamilies
| subdivision =
There are 7 subfamilies:<br>
Subfamily [[Arundinoideae]]<br>
Subfamily [[Bambusoideae]]<br>
Subfamily [[Centothecoideae]]<br>
Subfamily [[Chloridoideae]]<br>
Subfamily [[Panicoideae]]<br>
Subfamily [[Pooideae]]<br>
Subfamily [[Stipoideae]]<br>
}}
The family '''Poaceae''', in the Class [[Liliopsida]] of the [[Magnoliophyta|flowering plants]], is also known as '''Gramineae'''. Plants of this family are usually called '''[[grass]]es'''. There are about 600 [[genus|genera]] and between 9,000-10,000 [[species]] of grasses (Kew Index of World Grass Species). Plant communities dominated by Poaceae are called [[grassland]]s; it is estimated that grasslands comprise 20% of the vegetation cover of the earth. This family is the most important of all plant families to human economies: it includes the staple [[food]] grains grown around the world, lawn and forage grasses, and [[bamboo]], widely used for construction throughout [[Asia]].
The term "grass" is also applied to many [[Grass#Other plants called grass|grass-like plants not in the Poaceae]], leading to plants of the Poaceae often being called "true grasses".
== Structure and growth ==
Grasses generally have the following characteristics (it is advisable to have a look at the image gallery for reference):
;General aspects
[[Image:Grass-plant-structure.png|250px|thumb|left|Structure of a grass plant.]]
Poaceae have hollow [[Plant stem|stems]] called '''''[[culm]]s''''', plugged at intervals called '''''nodes'''''. [[Leaf|Leaves]] are alternate, ''distichous'' (in one plane) or rarely spiral, parallel-veined and arise at the nodes. Each leaf is differentiated into a lower '''''sheath''''' hugging the stem for a distance and a '''''blade''''' with margin usually entire. The leaf blades of many grasses are hardened with [[silica]] [[phytolith]]s, which helps discourage grazing animals. In some grasses (such as [[sword grass]]) this makes the grass blades sharp enough to cut human skin. A membranous appendage or fringe of hairs, called the '''''[[ligule]]''''', lies at the junction between sheath and blade, preventing water or insects to penetrate into the sheath.
Grass blades grow at the base of the blade and not from growing tips. This location of the grass growing point near the ground allows it to be [[grazing|grazed]] regularly without damage to the growing point.
;Reproduction
[[Image:En_Anatomia.png|Parts of a spikelet|thumb|300px|left]]
[[Flower]]s of Poaceae are peculiar. They are typically arranged in a terminal '''''[[Raceme|panicle or spike]]''''' made of many small '''''spikelets''''', each spikelet having one or more florets (flowers). The florets are usually hermaphroditic ([[maize]], monoecious, is an exception) and [[pollination]] is always [[anemophily|anemophilous]]. The [[perianth]] is reduced. Each spikelet is protected by two (usually) [[bract]]s called '''''glumes''''' and each single floret is surrounded by two bracts called the '''''lemma''''' (the external one) and the '''''palea''''' (the internal). This complex structure can be seen in the image on the left, portraying a [[wheat]] (''Triticum aestivum'') spike.
The [[fruit]] of Poaceae is a ''[[caryopsis]]''.
Grass plants also spread out from a parent plant. [[Plant habit|Growth habit]] describes the type of shoot growth present in particular grass plants and is directly related to their ability to spread out from the parent plant and ultimately form a [[clonal colony]]. There are three general classifications of growth habit present in grasses; bunch-type, [[stolon]]iferous, and [[
rhizome|rhizomatous]].
The success of the grasses lies in part in their morphology and growth processes, and in part in their physiological diversity. The grasses divide into two physiological groups, using the [[C3 carbon fixation|C3]] and [[C4 carbon fixation|C4]] photosynthetic pathways for carbon fixation. The C4 grasses have a photosynthetic pathway linked to specialised [[C4 carbon fixation#C4 Leaf Anatomy|Kranz]] leaf anatomy that particularly adapts them to hot climates and an atmosphere low in [[carbon dioxide]].
==Grass evolution==
Until recently grasses were thought to have evolved around 55 million years ago, based on fossil records. However, recent findings of 65-million-year-old [[phytolith]]s resembling grass phytoliths (including ancestors of [[rice]] and [[bamboo]]) in [[Cretaceous]] [[dinosaur]] [[coprolite]]s<ref>{{cite web |url=http://www.sciencemag.org/cgi/content/summary/310/5751/1126 |title=Dinosaurs Dined on Grass |publisher=Science Magazine |author=Dolores R. Piperno and Hans-Dieter Sues |date=18 November 2005 |accessdate=2007-03-23}}</ref>, may place the diversification of grasses to an earlier date.
The [[flower]]s of grass are reduced from the general [[monocotyledon]] type. The immediate ancestor of the first grass may have been a small Liliaceous plant with rhizomes and many small flowers, growing in dense patches, which adopted [[wind]] pollination to escape limitations caused by shortage of [[insect]]s to [[pollinate]] the flowers.
==Cultivation and uses==
Agricultural grasses grown for their edible seeds are called ''[[cereal]]s''. Cereals constitute the major source of [[carbohydrate]] for humans and perhaps the major source of protein, and include [[rice]] in southern and eastern Asia, [[maize]] in [[Central America|Central]] and [[South America]], and [[wheat]] and [[barley]] in [[Europe]], northern Asia and the [[Americas]]. Some other grasses are of major importance for foliage production. [[Sugarcane]] is the major source of [[sugar]] production. Many other grasses are grown for [[forage]] and [[fodder]] for [[animal]] food, particularly for [[sheep]] and [[cattle]].
Grasses are used for construction; larger [[bamboo]]s and ''[[Arundo donax]]'' have stout culms that can be used in a manner similar to timber, and grass roots stabilize the sod of [[sod house]]s. ''Arundo'' is used to make reeds for [[woodwind instrument]]s, and bamboo is used for innumerable implements.
Grass [[fiber|fibre]] can be used for making [[paper]], and for [[biofuel]] production. Grasses are the primary plant used in [[lawn]]s, which themselves derive from grazed [[grassland]]s in Europe. ''[[Phragmites|''Phragmites australis'']]'' (common reed) is important in water treatment, wetland habitat preservation and land reclamation in the [[Old World]].
Grasses are used as food plants by many species of [[butterflies]] and [[moths]]. see [[List of Lepidoptera which feed on grasses]].
===Economically important grasses===
{|
|- valign=top
|
;[[Grain|Grain crops]]
*[[Barley]]
*[[Maize]] (Corn)
*[[Oats]]
*[[Rice]]
*[[Rye]]
*[[Sorghum]]
*[[Wheat]]
*[[Millet]]
|
;Leaf and stem crops
*[[Bamboo]]
*[[Marram grass]]
*[[Poa|Meadow-grass]]
*[[Phragmites|Reed]]
*[[Ryegrass]]
*[[Sugarcane]]
|
;[[Lawn|Lawn grasses]]
*[[Bahia grass]]
*[[Agrostis|Bent grass]]
*[[Cynodon|Bermuda grass]]
*[[Festuca|Fescue]]
*[[Poa|Meadow-grass]]
*[[Ryegrass]]
*[[Zoysia]]
|
;[[Model organism]]s
*''[[Brachypodium distachyon]]''
*[[Maize]] (Corn)
*[[Rice]]
*[[Sorghum]]
*[[Wheat]]
|}
==Grass and society==
[[Image:Grass covered house in Iceland 1972.jpg|thumb|Grass covered house in Iceland]]
Grass has long had significance in human society. It has been cultivated as a food source for [[domesticated animals]] for up to 10,000 years, and has been used to make [[paper]] since at least as early as [[2400 B.C.]]
Some [[idiom]]s evoke images of grass. For example:
*"The grass is always greener on the oth
er side" suggests that the greenness of grass is a positive quality.
*"Don't let the grass grow under your feet" references the speed with which grass grows.
*"A [[snake]] in the grass" cautions about the dangers that may be hidden in the grass.
*"When [[elephants]] fight, it is the grass who suffers" personifies the grass.
==Image gallery==
<gallery>
Image:Ruwbeemdgras_Poa_trivialis_ligula.jpg|Leaves of ''Poa trivialis'' showing the ligules
Image:Bamboo_DSCN2465.jpg|Bamboo stem and leaves, nodes are evident
Image:En_Spica_spiculae.png|Wheat spike and spikelet
Image:En_Aperta.png|Spikelet opened to show caryopsis
Image:Harestail grass.jpg|Harestail Grass
Image:Gras.jpg|Grass
Image:Saccharum-officinarum2.JPG|Sugarcane (''Saccharum officinarum'')
Image:Bromus_hordeaceus_unten.jpeg|Roots of ''Bromus hordeaceus''
Image:Ohra.jpg|Barley mature spikes (''Hordeum vulgare'')
Image:Koeh-283.jpg|Illustration depicting both staminate and pistillate flowers of maize (''Zea mays'')
</gallery>
== See also ==
* [[agrostology]]
* [[grass]]
* [[Cyperaceae|sedges]]
==References==
{{reflist}}
== External links and references ==
* [http://www.turffiles.ncsu.edu TurfFiles] by [[North Carolina State University]]
* [http://www.rbgkew.org.uk/data/grasses-db/sppindex.htm Kew Index of World Grass Species]
* [http://forages.oregonstate.edu/projects/regrowth/main.cfm?PageID=11 Definitions of Grass structures]
* [http://delta-intkey.com/angio/www/graminea.htm Poaceae] in L. Watson and M. J. Dallwitz] (1992 onwards), [http://delta-intkey.com/angio/ The families of flowering plants.]
Chapman, G.P. and W.E. Peat. 1992. An Introduction to the Grasses. CAB International, Wallingford.
Cheplick, G.P. 1998. Population Biology of Grasses. Cambridge Univ. Press, Cambridge.
* L. Watson and M. J. Dallwitz (1992 onwards). [http://delta-intkey.com/grass/ The grass genera of the world.]
*Piperno, D. R. & Sues, H.-D. (2005). Paleontology: Dinosaurs Dined on Grass. ''Science'' 310 (5751): 1126-1128 (18 November 2005) [http://www.sciencemag.org/cgi/content/summary/310/5751/1126 summary].
* [http://utc.usu.edu/keys/default.htm Interactive Keys to North American Grasses at Utah State University]
[[Category:Poales| Poaceae]]
[[Category:Plant families]]
[[Category:Grasses]]
[[Category: gardening]]
