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

Grazing and livestock feed
Festuca - fescue
Sorghum - milo, sorghum
Setaria - millet
Zea - corn

Lawn grasses
Poa - blue grass
Cynodon - Bermuda

Weeds - many, worst is probably Sorghum halepense (Johnson grass)

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 hexaploidthat contains genetic material from three different species.

There are currently 20,000 cultivars of bread wheats.

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