Poaceae ( ), also called Gramineae ( ), is a large and nearly ubiquitous family of commonly known as grasses. It includes the cereal grasses, , the grasses of natural grassland and species cultivated in and pasture. The latter are commonly referred to collectively as grass.
With around 780 genera and around 12,000 species,
The Poaceae are the most economically important plant family, providing from domesticated cereal crops such as maize, wheat, rice, oats, barley, and millet for people and as forage for livestock. They provide, through direct human consumption, just over one-half (51%) of all dietary energy; rice provides 20%,
Grasses have Plant stem that are hollow except at the nodes and narrow alternate leaves borne in two ranks. The lower part of each leaf encloses the stem, forming a leaf-sheath. The leaf grows from the base of the blade, an adaptation allowing it to cope with frequent grazing.
such as savannah and prairie where grasses are dominant are estimated to constitute 40.5% of the land area of the Earth, excluding Greenland and Antarctica.
Though they are commonly called "grasses", groups such as the seagrasses, Juncaceae and Cyperaceae 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 the order Alismatales. However, all of them belong to the monocot group of plants.
Description
Grasses may be
annual plant or
perennial plant Herbaceous plant,
generally with the following characteristics (the image gallery can be used for reference): The
Plant stem 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
Leaf are nearly always alternate and distichous (in one plane), and have parallel veins.
Each leaf is differentiated into a lower sheath hugging the stem and a blade with entire (i.e., smooth) margins.
The leaf blades of many grasses are hardened with
silica , 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.
of Poaceae are characteristically arranged in , each having one or more florets.
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
grazing or
lawnmower regularly without severe damage to the plant.
Three general classifications of growth habit present in grasses: bunch-type (also called caespitose), , and rhizome.
The C3 grasses are referred to as "cool-season" grasses, while the C4 plants are considered "warm-season" grasses.
-
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 , is C4.
Taxonomy
The name Poaceae was given by John Hendley Barnhart in 1895,
based on the tribe Poeae described in 1814 by Robert Brown, and the type genus
Poa described in 1753 by
Carl Linnaeus. The term is derived from the Ancient Greek .
Evolutionary history
Grasses include some of the most versatile
. They became widespread toward the end of the
Cretaceous period, and fossilized
dinosaur dung (
) belonging to the
Sauropoda Titanosauria (though this provenance has been questioned)
have been found containing
of a variety that include grasses that are related to modern
rice and
bamboo.
Grasses have adapted to conditions in lush
, dry
, cold mountains and even intertidal habitats, and are currently the most widespread plant type; grass is a valuable source of food and energy for all sorts of wildlife.
A cladogram shows subfamilies and approximate species numbers in brackets:[ ]
Before 2005, fossil findings indicated that grasses evolved around 55 million years ago. Finds of grass-like in Cretaceous dinosaur from the latest Cretaceous (Maastrichtian) aged Lameta Formation of India have pushed this date back to 66 million years ago.
In 2018, a study described grass microfossils extracted from the teeth of the Hadrosauroidea dinosaur Equijubus normani from northern China, dating to the Albian stage of the Early Cretaceous approximately 113–100 million years ago, which were found to belong to primitive lineages within Poaceae, similar in position to the Anomochlooideae. These are currently the oldest known grass fossils.
Fossils of Phragmites have been found in the Late Cretaceous of North America, particularly in the Maastrichtian aged Laramie Formation.
The relationships among the three subfamilies Bambusoideae, Oryzoideae and Pooideae in the BOP clade have been resolved: Bambusoideae and Pooideae are more closely related to each other than to Oryzoideae.
According to Lester Charles King, the spread of grasses in the Neogene would have changed patterns of hillslope evolution favouring slopes that are convex upslope and concave downslope and lacking a escarpment were common. King argued that this was the result of more slowly acting surface wash caused by carpets of grass which in turn would have resulted in relatively more downhill creep.
Subdivisions
There are about 12,000 grass species in about 771 genera that are classified into 12 subfamilies.
[ ] See the full list of Poaceae genera.
-
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, Mikio Kobayashi, Sarah Mathews, Spangler & E.A.Kellogg, a small lineage of the African genus Puelia
-
Pooideae, including wheat, barley, , brome-grass ( Bromus), reed-grasses ( Calamagrostis) and many lawn and pasture grasses such as bluegrass ( Poa)
-
Bambusoideae, including bamboo
-
Ehrhartoideae, including rice and wild rice
-
Aristideae, including Aristida
-
Arundinoideae, including giant reed and common reed
-
Chloridoideae, including the lovegrasses ( Eragrostis, about 350 species, including teff), dropseeds ( Sporobolus, some 160 species), finger millet ( Eleusine coracana (L.) Gaertn.), and the muhly grasses ( Muhlenbergia, about 175 species)
-
Panicoideae, including panic grass, maize, sorghum, sugarcane, most , fonio, "Job's tears", and
-
Micrairoideae
-
Danthonioideae, including Cortaderia
Distribution
The grass family is one of the most widely distributed and abundant groups of plants on
Earth. Grasses are found on every continent,
including
Antarctica. The Antarctic hair grass,
Deschampsia antarctica is one of only two flowering plant species native to the western Antarctic Peninsula.
Ecology
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
are called grasslands. If only large, contiguous areas of grasslands are counted, these biomes cover 31% of the planet's land.
Grasslands include
pampas,
, and
.
Grasses provide food to many grazing mammals,
as well as to many species of
Butterfly and
.
Many types of animals eat grass as their main source of food, and are called
– these include
cattle,
sheep,
,
and many
, such as
and the caterpillars of many
Satyridae. Grasses are also eaten by
Omnivore or even occasionally by primarily
Carnivore animals.
Grasses dominate certain , especially temperate grasslands, because many species are adapted to grazing and fire.
Grasses are unusual in that the meristem is near the bottom of the plant; hence, grasses can quickly recover from cropping at the top.
Sexual reproduction and meiosis
Sexual reproduction and
meiosis have been studied in
rice,
maize,
wheat and
barley.
Meiosis research in these crop species is linked to crop improvement, since meiotic recombination is an important component of
plant breeding.
Unlike in animals, the specification of both male and female plant
occurs late in development during flowering. The transition from the
sporophyte phase to the
gametophyte state is initiated by meiotic entry.
Uses
Grasses are, in human terms, perhaps the most economically important plant family.
Their economic importance stems from several areas, including food production, industry, and
. They have been grown as food for domesticated animals for up to 6,000 years and the grains of grasses such as
wheat, rice, maize (corn) and
barley have been the most important human
. Grasses are also used in the manufacture of
thatching,
paper,
fuel,
clothing, insulation, timber for
fence,
furniture,
scaffolding and
construction materials, floor
matting, sports turf and
basket weaving.
Food production
Of all crops grown, 70% are grasses.
Agricultural grasses grown for their edible seeds are called
or
(although the latter term, when used agriculturally, refers to both cereals and similar seeds of other plant species, such as
buckwheat and
legumes). Three cereals—rice, wheat, and maize (corn)—provide more than half of all calories consumed by humans.
Cereals constitute the major source of
for humans and perhaps the major source of protein; these include rice (in
South Asia and
eastern Asia), maize (in
Central America and
South America), and wheat and barley (in
Europe,
northern Asia and the
Americas).
Sugarcane is the major source of sugar production. Additional food uses of sugarcane include sprouting, shoots, and , and in drink they include sugarcane juice and plant milk, as well as rum, beer, whisky, and vodka.
are used in numerous Asian dishes and broths, and are available in supermarkets in various sliced forms, in both fresh, fermented and canned versions.
Lemongrass is a grass used as a culinary herb for its citrus-like flavor and scent.
Many species of grass are grown as pasture for foraging or as fodder for prescribed livestock feeds, particularly in the case of cattle, , and sheep. Such grasses may be cut and stored for later feeding, especially for the winter, in the form of bales of hay or straw, or in silos as silage. Straw (and sometimes hay) may also be used as bedding for animals.
An example of a sod-forming perennial grass used in agriculture is Thinopyrum intermedium.
Industry
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 such as oriented structural straw board. Grass
fiber can be used for making paper,
biofuel production,
nonwoven fabrics, and as replacement for glass fibers used in reinforced plastics.
Bamboo scaffolding is able to withstand typhoon-force winds that would break steel scaffolding.
Larger bamboos and
Arundo donax have stout culms that can be used in a manner similar to timber,
Arundo is used to make reeds for woodwind instruments, and bamboo is used for innumerable implements.
Phragmites (common reed) is important for thatching and wall construction of homes in Africa.
Palaeoecological reconstructions
Pollen morphology, particularly in the
Poaceae family, is key to figuring out their evolutionary relationships and
Paleoecology.
Grass pollen grains, however, often look the same, making it hard to use them for detailed climate or environmental reconstructions.
Grass pollen has a single pore and can vary a lot in size, from about 20 to over 100 micrometers, and this size difference has been looked into for clues about past habitats, to tell apart
domesticated grasses from wild ones,
and to indicate various biological features like how they perform
photosynthesis,
their breeding systems,
and genetic complexity.
Yet, there's ongoing debate about how effective pollen size is for piecing together historical landscapes and weather patterns, considering other factors such as genetic material amount might also affect pollen size.
Despite these challenges, new techniques in Fourier-Transform Infrared Spectroscopy (FT-IR) and improved statistical methods are now helping to better identify these similar-looking pollen types.
Lawn and ornamental use
Grasses are the primary plants used in lawns, which themselves derive from grazed
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), American football,
tennis,
golf,
cricket,
softball and
baseball.
Ornamental grasses, such as perennial , are used in many styles of garden design for their foliage, inflorescences and seed heads. They are often used in natural landscaping, xeriscaping and slope and beach stabilization in contemporary landscaping, , and native plant gardening. They are used as screens and hedges.
Sports turf
Grass playing fields, courses and pitches are the traditional playing surfaces for many
sports, including American football, association football,
baseball,
cricket,
golf, and
Rugby football. Grass surfaces are also sometimes used for
horse racing and
tennis. Type of maintenance and species of grass used may be important factors for some sports, less critical for others. In some sports facilities, including indoor domes and other places where maintenance of a grass field would be difficult, grass may be replaced with
artificial turf, a synthetic grass-like substitute.
Cricket
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.
Golf
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 turf grass varieties.
Tennis
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 court (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
A number of grasses are invasive species that damage natural ecosystems, including forms of Phragmites australis which are native to Eurasia but has spread around the world.
Role in society
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, each of which has been used for this purpose for over 4,000 years.
In some places, particularly in 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:
In communities with drought problems, watering of lawns may be restricted to certain times of day or days of the week.
The smell of freshly cut grass is produced mainly by cis-3-Hexenal.
Some common 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 fight, it is the grass that 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.
[Olmert, Michael (1996). Milton's Teeth and Ovid's Umbrella: Curiouser & Curiouser Adventures in History, p. 208. Simon & Schuster, New York. .]
Image gallery
File:Gräsfrön - Grass seeds - 2025.jpg|Grass seeds, a mixture of 90% Festuca rubra and 10% Festuca ovina.
File:Ruwbeemdgras Poa trivialis ligula.jpg|Leaves of Poa trivialis showing the
File:Bamboo DSCN2465.jpg|Bamboo stem and leaves, nodes are evident
File:Chasmanthium latifolium-spikelet.jpg|A Chasmanthium latifolium spikelet
File:En Spica spiculae.png|Wheat spike and spikelet
File:En Aperta.png|Spikelet opened to show caryopsis
File:Harestail grass.jpg|Harestail grass
File:Grass.jpg|Grass
File:Saccharum-officinarum2.JPG|Sugarcane ( Saccharum officinarum)
File:Bromus hordeaceus unten.jpeg|Roots of Bromus hordeaceus
File:Ohra.jpg|Barley mature spikes ( Hordeum vulgare)
File:Koeh-283.jpg|Illustration depicting both staminate and pistillate flowers of maize ( Zea mays)
File:Flowering Grass.JPG|A grass flower head (meadow foxtail) showing the plain-coloured flowers with large anthers
File:Grass Anthers.JPG|Anthers detached from a meadow foxtail flower
File:Setaria verticillata W IMG 1084.jpg| Setaria verticillata, bristly foxtail
File:Setaria verticillata W IMG 1083.jpg| Setaria verticillata, bristly foxtail
File:Oryza sativa in Kadavoor.jpg| Oryza sativa, Kerala, India
See also
External links
