POACEAE (GRAMINAE) - Grass Family
Perennial or annual herbs, stems (culms) erect, ascending,
prostrate or creeping, round, hollow or solid at internodes, solid at
nodes
Leaves - 2-ranked, alternate, composed of an open sheath, ligule and
blade, sheath encloses the culm
Florets - usually bisexual, sometimes unisexual. florets have 2
bracts - the outer is the lemma, the inner is the palea. Perianth is
reduced to 2 or 3 lodicules. Lodicules are not always present.
Styles feather-like
Basic unit of the inflorescence is the spikelet.
Spikelets can contain 1, 2, or more florets. Spikelets are usually
subtended by glumes
Fruit a caryopsis (grain), rarely a nut, berry, or utricle
500 genera, 8000 species, found anywhere vascular plants can
survive
Systematics
Grasses have been the subject of intensive investigation which has
resulted in many changes in classification, current classifications
recognize three to six subsubfamilies and up to 25 tribes
Common genera - almost too many to list
Panicum - panic grass -
largest genus in Poaceae
Festuca - fescue
Poa - blue grass
Andropogon - big bluestem - tall
prairie grass
Digitaria - crabgrass
Aristida - 3 awn grass
Arundinaria - giant cane - bamboo tribe
ECONOMIC IMPORTANCE - MOST IMPORTANT FAMILY
Food:
Avena - oats
Triticum - wheat - more produced
than any other
Secale - rye
Hordeum - barley
Saccharum - sugar cane
Oryza - rice
- most important for direct human consumption
Zea - corn (maize)
Grazing and livestock feed
Festuca - fescue
Sorghum - milo, sorghum
Setaria - millet
Zea - corn
Poa - blue grass
Cynodon - Bermuda
Weeds - many, worst is probably Sorghum halepense (Johnson
grass)
Medicinal uses - tea used as diuretic, diarrhea, sore throats,
sores, poison ivy.
ORIGIN OF WHEAT
Wild and early domesticates were diploid (2n=14) Triticum
monococcum
A natural mutation occurred that prevented shattering and was quickly
adopted. This cultivar is still grown in Yugoslavia and Turkey -
Einkorn wheat
By 8th Cent. B.C., Einkorn wheat hybridized with a wild goat
grass,exact identity unknown, which resulted in a tetraploid (4n=28)
called Triticum turgidum or Emmer wheat. One cultivar of Emmer
wheat underwent a mutation which caused the bases of the glumes to
collapse at maturity which made separation of the fruit from the
chaff easier, known as Durum wheat. Free-threshing wheats could
produce raised breads. Durum wheat now is grown mostly for pasta and
noodles in areas of low rainfall.
Final step in production of modern bread wheats resulted from Emmer
(4n) X Triticum sp. (2n) which yielded Triticum aestivum (6n),
which is a hexaploid that contains genetic material from three
different species.
There are currently 20,000 cultivars of bread wheats.
IMAGE GALLERY
FLOWERING PLANT GATEWAY (Poaceae)
(Graminae)
Grass Images Listed
Alphabetically