Blades of grass
POACEAE or GRAMINEAE is a large and nearly ubiquitous family of
monocotyledonous flowering plants known as GRASSES.
Grasslands such as savannah and prairie where grasses are dominant
are estimated to constitute 40.5% of the land area of the
Though they are commonly called "grasses", seagrasses , rushes , and sedges fall outside this family. The rushes and sedges are related to the Poaceae, being members of the order Poales , but the seagrasses are members of order Alismatales .
* 1 Etymology * 2 Evolutionary history * 3 Description * 4 Growth and development * 5 Distribution * 6 Ecology * 7 Taxonomy
* 8 Uses
* 8.1 Food production
* 8.2 Industry
* 8.5 Economically important grasses
* 9 Role in society * 10 In popular culture * 11 Image gallery * 12 See also * 13 References * 14 External links
Grasses include some of the most versatile plant life-forms . They
became widespread toward the end of the
A cladogram shows subfamilies and approximate species numbers in brackets:
Bambusoideae – bamboos (1450)
Before 2005, fossil findings indicated that grasses evolved around 55
million years ago. Recent findings of grass-like phytoliths in
Wu, You & Li (in press) described grass microfossils extracted from a
specimen of the hadrosauroid dinosaur
Equijubus normani from the Early
Grasses may be annual or perennial herbs, :10 generally with the following characteristics (the image gallery can be used for reference): The stems of grasses, called culms , are usually cylindrical (more rarely flattened, but not 3-angled) and are hollow, plugged at the nodes , where the leaves are attached. Grass leaves are nearly always alternate and distichous (in one plane), and have parallel veins. :11 Each leaf is differentiated into a lower sheath hugging the stem and a blade with entire (i.e., smooth) margins. :11 The leaf blades of many grasses are hardened with silica phytoliths , which discourage grazing animals; some, such as sword grass , are 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 from penetrating into the sheath. :11 Parts of a spikelet
GROWTH AND DEVELOPMENT
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 grazed or mown regularly without severe damage to the plant. :113–114
Three general classifications of growth habit present in grasses: bunch-type (also called caespitose), stoloniferous , and rhizomatous . The success of the grasses lies in part in their morphology and growth processes and in part in their physiological diversity. Most of the grasses divide into two physiological groups, using the C3 and C4 photosynthetic pathways for carbon fixation. The C4 grasses have a photosynthetic pathway, linked to specialized Kranz leaf anatomy, which allows for increased water use efficiency , rendering them better adapted to hot, arid environments and those lacking in carbon dioxide .
The C3 grasses are referred to as "cool-season" grasses, while the C4 plants are considered "warm-season" grasses. :18–19
* Annual cool-season - wheat , rye , annual bluegrass (annual
Poa annua ), and oat
A kangaroo eating grass Wind-blown grass in the Valles
Grasses are the dominant vegetation in many habitats, including grassland , salt-marsh , reedswamp and steppes . They also occur as a smaller part of the vegetation in almost every other terrestrial habitat. Grass-dominated biomes are called grasslands. If only large, contiguous areas of grasslands are counted, these biomes cover 31% of the planet's land. Grasslands include pampas , steppes , and prairies . Grasses provide food to many grazing mammals—such as livestock, deer, and elephants—as well as to many species of butterflies and moths . Many types of animals eat grass as their main source of food, and are called graminivores – these include cattle , sheep , horses , rabbits and many invertebrates , such as grasshoppers and the caterpillars of many brown butterflies . Grasses are also eaten by omnivorous or even occasionally by primarily carnivorous animals.
Grasses are unusual in that the meristem is located near the bottom of the plant; hence, they can quickly recover from cropping at the top. The evolution of large grazing animals in the Cenozoic contributed to the spread of grasses. Without large grazers, fire-cleared areas are quickly colonized by grasses, and with enough rain, tree seedlings. Trees eventually outcompete most grasses. Trampling grazers kill seedling trees but not grasses. :137
There are about 12,000 grass species in about 771 genera that are
classified into 12 subfamilies. See the full list of
* Anomochlooideae Pilg. ex Potztal , a small lineage of broad-leaved grasses that includes two genera (Anomochloa, Streptochaeta) * Pharoideae L.G.Clark & Judz. , a small lineage of grasses of three genera, including Pharus and Leptaspis * Puelioideae L.G.Clark, M.Kobay. , S.Mathews , Spangler margin-right:auto; overflow:hidden; width:auto; max-width:1508px;"> Grazing cattle on a pasture near Hradec nad Moravicí in Czech Silesia .
Agricultural grasses grown for their edible seeds are called cereals
or grains (although the latter term, agriculturally, refers to both
cereals and legumes ). Three cereals – rice , wheat , and maize
(corn) – provide more than half of all calories eaten by humans. Of
all crops, 70% are grasses. Cereals constitute the major source of
carbohydrates for humans and perhaps the major source of protein, and
include rice in southern and eastern Asia , maize in Central and South
America , and wheat and barley in
Lemongrass is used as a culinary herb for its scent.
Many species of grasses are grown as pasture for forage and fodder
for livestock , particularly for sheep and cattle . They may be cut
and stored in the form of hay , straw or silage for use during the
Grasses are used as raw material for a multitude of purposes,
including construction and in the composition of building materials
such as cob , for insulation, in the manufacture of paper and board
Oriented structural straw board . Grass fiber can be used for
making paper , and for biofuel production.
Phragmites australis (common reed) is important for thatching and
grass roots stabilize the sod of sod houses . Reeds are used in water
treatment systems, in wetland conservation and land reclamation in
LAWN AND ORNAMENTAL USE
Grasses are the primary plant used in lawns , which themselves derive
from grazed grasslands in Europe. They also provide an important means
of erosion control (e.g., along roadsides), especially on sloping
land. Grass lawns are an important covering of playing surfaces in
many sports, including football (soccer) ,
Ornamental grasses , such as perennial bunch grasses , are used in many styles of garden design for their foliage, inflorescences, seed heads. They are often used in natural landscaping , xeriscaping and slope stabilization in contemporary landscaping, wildlife gardening , and native plant gardening .
Grass playing fields, courses and pitches are the traditional playing
surfaces for many sports , including
The gray area is the CRICKET pitch currently in use. Parallel to
it are other pitches in various states of preparation which could be
used in other matches. Main article:
In cricket, the pitch is the strip of carefully mowed and rolled grass where the bowler bowls. In the days leading up to the match it is repeatedly mowed and rolled to produce a very hard, flat surface for the ball to bounce off.
Grass on golf courses is kept in three distinct conditions: that of the rough, the fairway, and the putting green. Grass on the fairway is mown short and even, allowing the player to strike the ball cleanly. Playing from the rough is a disadvantage because the long grass may affect the flight of the ball. Grass on the putting green is the shortest and most even, ideally allowing the ball to roll smoothly over the surface. An entire industry revolves around the development and marketing of grass varieties for golf courses.
Main article: Grass court
In tennis, grass is grown on very hard-packed soil, and the bounce of a tennis ball may vary depending on the grass's health, how recently it has been mowed, and the wear and tear of recent play. The surface is softer than hard courts and clay (other tennis surfaces), so the ball bounces lower, and players must reach the ball faster resulting in a different style of play which may suit some players more than others. Among the world's most prestigious court for grass tennis is Centre Court at Wimbledon, London which hosts the final of the annual Wimbledon Championships in England, one of the four Grand Slam tournaments.
ECONOMICALLY IMPORTANT GRASSES
Ornamental grasses (Horticultural )
ROLE IN SOCIETY
Grass-covered house in
Grasses have long had significance in human society. They have been cultivated as feed for people and domesticated animals for thousands of years. The primary ingredient of beer is usually barley or wheat, both of which have been used for this purpose for over 4,000 years.
In some places, particularly in suburban areas, the maintenance of a grass lawn is a sign of a homeowner's responsibility to the overall appearance of their neighborhood. One work credits lawn maintenance to:
...the desire for upward mobility and its manifestation in the lawn. As Virginia Jenkins, author of The Lawn, put it quite bluntly, 'Upper middle-class Americans emulated aristocratic society with their own small, semi-rural estates.' In general, the lawn was one of the primary selling points of these new suburban homes, as it shifted social class designations from the equity and ubiquity of urban homes connected to the streets with the upper-middle class designation of a "healthy" green space and the status symbol that is the front lawn.
Many US municipalities and homeowners' associations have rules which require lawns to be maintained to certain specifications, sanctioning those who allow the grass to grow too long. In communities with drought problems, watering of lawns may be restricted to certain times of day or days of the week.
The smell of the freshly cut grass is produced mainly by cis-3-Hexenal .
Some common aphorisms involve grass. For example:
* "The grass is always greener on the other side" suggests an alternate state of affairs will always seem preferable to one's own. * "Don't let the grass grow under your feet" tells someone to get moving. * "A snake in the grass" means dangers that are hidden. * "When elephants fight, it is the grass which suffers" tells of bystanders caught in the crossfire.
A folk myth about grass is that it refuses to grow where any violent death has occurred.
IN POPULAR CULTURE
* In John Christopher 's
The Death of Grass
Leaves of Poa trivialis showing the ligules *
A Chasmanthium latifolium spikelet *
Spikelet opened to show caryopsis *
Harestail grass *
Roots of Bromus hordeaceus *
Illustration depicting both staminate and pistillate flowers of maize
A grass flower head (meadow foxtail) showing the plain-coloured flowers with large anthers. *
Anthers detached from a meadow foxtail flower *
Setaria verticillata , bristly foxtail *
Setaria verticillata , bristly foxtail *
* ^ A B Yan Wu; Hai-Lu You; Xiao-Qiang Li (2017).
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