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Chaff
From Wikipedia, the free encyclopedia
Chaff (pronounced to rhyme with "half") is a term from agriculture used for the bracts and casings that are not edible and are harvested with the cereal grain. These casings include hulls or husks and part of the pericarp. The chaff is a byproduct of grain production and is often used for animal feed, while the grain is often made into flour.
See below for other meanings.
Etymology: From Middle English chaf, from Old English ceaf; related to Old High German cheva meaning husk.
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In botany the bracts are called glumes. The bracts and husks are harvested with cereal grains such as rice and wheat and separated from the grain, by such techniques as threshing and wind winnowing.
A bract is a modified or specialized leaf, from the axil of which a flower or flower stalk arises; or a bract may be any leaf associated with an inflorescence. In grasses (Poaceae), the bracts that enclose the florets are termed glumes. They are sterile bracts found below the flowers in a spikelet, the basic unit of a grass inflorescence. Spikelets typically have two basal glumes, with one or more florets above. However, one or, more rarely, both glumes may be lacking in some taxa.[1] Four wild species of wheat, and in the domesticated einkorn[2], emmer[3] and spelt[4] wheats are hulled (in German, Spelzweizen). This more primitive morphology consists of toughened glumes that tightly enclose the grains, and (in domesticated wheats) a semi-brittle rachis that breaks easily on threshing. The result is that when threshed, the wheat ear breaks up into spikelets. To obtain the grain, further processing, such as milling or pounding, is needed to remove the hulls or husks. In contrast, in free-threshing (or naked) forms such as durum wheat and common wheat, the glumes are fragile and the rachis tough. On threshing, the chaff breaks up, releasing the grains. Hulled wheats are often stored as spikelets because the toughened glumes give good protection against pests of stored grain.[2]
Hay or straw cut into very short lengths is also called chaff (it serves the same agricultural purposes). The cutting is often done by a specially designed machine called a chaff cutter and fed to horses or cattle.
In botany, chaff refers to the receptacular bracts of many species in the sun flower family Asteraceae. They are modified leaves that are scale like and surround single flowers in the head. Note the inside of a sun flower inflorescence. They are often called chaffy bracts, which act as spacers between the flowers
Chaff is also used to refer to something worthless, such as in the expression "separating the wheat from the chaff", meaning to find things of value and separate them from things of no value. For example Psalm 1 of the Bible says: "Not so the wicked! They are like chaff that the wind blows away".
Radar reflecting strips called "chaff" which reflect sufficient radar energy back to the radar system so as to be detectable, i.e. "visible", by the radar system. The hope is multiple radar returns make determination of the true threat more difficult; separating the "good from the bad". Hence the military's logical appropriation of the term.
- ^ Grass Structures
- ^ a b Potts, D. T. (1996) Mesopotamia Civilization: The Material Foundations Cornell University Press. p. 62. ISBN 0-8014-3339-8.
- ^ Nevo, Eviatar & A. B. Korol & A. Beiles & T. Fahima. (2002) Evolution of Wild Emmer and Wheat Improvement: Population Genetics, Genetic Resources, and Genome.... Springer. p. 8. ISBN 3-540-41750-8.
- ^ Vaughan, J. G. & P. A. Judd. (2003) The Oxford Book of Health Foods. Oxford University Press. p. 35. ISBN 0-19-850459-4.