PoaceaeGramineae Grass Family

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Poaceae/Gramineae (Grass Family)
Habit herbs, often rhizomatous, but trees in
tropical bamboos Stems jointed, round to
elliptical in cross-section, solid to hollow,
with silica bodies Leaves alternate, 2-ranked,
consisting of sheath, ligule, and blade, sheaths
tightly encircling the stem, the margins
overlapping but not fused or, occationally,
united to form a tube, blades simple, usually
linear, usually with parallel venation Infloresce
nce a spike, panicle, cyme, or raceme of
spikelets
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Spikelet composed of an axis bearing 2-ranked and
closely overlapping basal bracts (glumes) and
florets, breaking up above the glumes or
remaining intact at maturity, compressed parallel
or perpendicular to the plane of arrangement of
glumes and florets, glumes usually 2, equal in
size or unequal Florets 1 to numerous per
spikelet, made up of a bract (the lemma)
subtending a flower and another bract (the palea,
a prophyll) lying between the flower and the
spikelet axis, lemmas sometimes with 1 or more
needle-lie, straight or bent awns, palea often
translucent, smaller than, and partially enclosed
by the lemma
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Flowers small, bisexual or unisexual, usually
wind-pollinated, greatly reduced in size and
number of floral parts, lodicules ( perianth
parts) mostly 2, translucent Stamens (1-)3(-6,
or numerous), anthers usually sagittate Pollen
monoporate Carpels 3, but often appearing as 2,
connate, stigmas 2 (-3), plumose, ovary
superior Fruit a single-seeded caryopsis (grain)
with fruit wall fused to the seed, embryo with a
highly modified cotyledon (scutellum), lateral in
position.
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Floral Formula Floral Diagram
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Distribution and Ecology cosmopolitan in desert
to freashwater and marine habitats, and at all
but the highest elevations. Genera/species ca.
650/9700 Economic plants and products The
economic importance of grasses lies in their
paramount role as food about 70 of the worlds
farmland is planted in crop grasses, and over 50
of humanities calories come from grasses. People
have cultivated cereals for at least 10,000
years. From the beginning of their
domestication, wheat (Triticum aestivum), barley
(Hordeum vulgare), and oats (Avena sativa) in the
Near East, sorghum (Sorghum bicolor) and pearl
millet (Pennisetum americanum) in Africa, rice
(Oryza sativa) in southeastern Asia, and maize or
corn (Zea mays) in Meso-America have made
possible the rise of civilization.
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In terms of global production, the four most
important crops are grasses sugarcane (Saccharum
officinale), wheat, rice, and maize. Barley and
sorghum are in the top twelve. Grasses are also
used for livestock food, erosion control, turf
production, and as a sugar source for
fermentation of alcoholic beverages, such as beer
and whiskey. Subfamilial phylogenetic
relationships- Grasses are easily recognized, and
their monophyly has been supported by
morphological and DNA characters. Recent
molecular systematic studies support the
recognition of 12 subfamilies. Anomochlooideae
(native to Brazil), Pharoideae (Old and New World
tropics), and Puelioideae (West Africa) are the
three earliest diverging lineages, and together
include only about 25 of the almost 10,000
species of the family.
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The remaining species fall into two large groups.
One group (the BEP clade) includes Bambusoideae
s.s., Ehrhartoideae, and Pooideae, and the other
(the PAC-CAD clade) includes Panicoideae,
Arundinoideae s.s., Chloridoideae,
Centothecoideae, Aristidoideae, and Danthonoideae.
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Bambusoideae s.s. includes both woody and
herbaceous plants, and are almost exclusively
tropical in distribution. Woody bamboos have
stems up to 40 m in height. Important genera of
woody bamboos are Bambusa (120 spp.), Chusquea
(100 spp.), Arundinaria (50 spp.), Sasa (50
spp.), and Phyllostachys (45 spp.).
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Arthrostylidium haitiense
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Bambusa ventricosa
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Ehrhartoideae include the Southern Hemisphere
Ehrharteae, as well as the widespread Oryzeae.
The most widely known Oryzeae are the
commercially important Asian rice (Oryza sativa)
and North American wild rice (Zizania aquatica).
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Oryza sativa
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Pooideae are largely temperate in distribution,
especially in the Northern Hemisphere. Important
genera include several cereals (wheat, barley,
oats) as well as rye (Secale cereale), turf
grasses (e.g., bluegrasses, Poa, 500 spp.),
fescues (Festuca, 450 spp.), pasture grasses
(e.g., Phleum, Dactylis), and some weeds (e.g.,
Agrostis, 220 spp., and Poa). Other important
grasses of this subfamily are Stipa (300 spp.),
Calamagrostis (270 spp.), Bromus (150 spp.), and
Elymus (150 spp.).
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Poa annua
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Festuca elatior
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Avena sativa
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Elymus canadensis
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Triticum aestivum
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Triticum aestivum
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Stipa spartea
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Stipa spartea
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Chloridoideae bear distinctive bicellular hairs
on the leaf epidermis these may be synapomorphic
for a subset of the group. All but two
chloridoids show C4 photosynthesis. The
subfamily is best developed in arid and semiarid
tropical regions. Centers of distribution in
Africa and Australia suggest a Southern
Hemisphere origin. Some important genera are
Eragrostis (350 spp.), Muhlenbergia (160 spp.),
Sporobolus (160 spp.), Chloris (55 spp.),
Spartina (15 spp.), and Eustachys (10 spp.).
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Sporobolus heterolepis
Sporobolus junceus
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Oplismenus hirtellus subsp. setarius
Spartina patens
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Dactyloctenium aegypticum
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Stenotaphrum secundatum
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Panicoideae have long been recognized
taxonomically because of their distinctive
spikelets. The subfamily is primarily tropical
and contains two large tribes, Andropogoneae and
Paniceae, along with a number of small groups.
Important genera include Panicum (470 spp.),
Paspalum (330 spp.), Andropogon (100 spp.),
Setaria (100 spp.), Sorghum (20 spp.), and Zea (4
spp.).
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Andropogon glomeratus var. pumilus
Andropogon gerardii
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Schizachyrium scoparium
Sorghastrum secundum
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Sorghastrum nutans
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Panicum sp.
Paspalum notatum
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Cenchrus incertus
Cenchrus longispinus
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Zea mays subsp. mays
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Zea mays subsp. mays
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Zea mays subsp. mays
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Zea mays subsp. mexicana
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Zea mays subsp. mexicana
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Zea mays subsp. parviglumis
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The other subfamilies in the PACCAD clade are
structurally and genetically diverse. They range
from small desert species (Aristida, 250 spp.) to
giant wetland reeds (Phragmites, in the
Arundinoideae s.s.).
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Aristida spiciformis
Aristida sp.
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Arundo donax
Danthonia domingensis
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Uniola paniculata
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Uniola paniculata