Wednesday, September 23, 2009
Family Graminae (Poaceae), its Examples and Economic Importance
It is commonly called grass family belonging to Monocotyledons.
Mostly annual or perennial herbs or shrubs, sometimes tree like as in bamboos.
Root: Adventitious, fibrous, fascicled, still (Maize).
Stem: The prevailing type aerial stem is corn, sorghum and sugar canes. Among perennial members the stem may be a runner extending over considerable distance or a rhizome or a root stock serving for vegetative propagation. Small tubes and corns are found in few species.
Inflorescence: Variable, compound of several spikelets which are combined in various ways on a main axis called the rachis. Some are in compound spikes as in wheat, others are racenes as in Fastuna while still others are panicles as in oats. Mostly inflorescence is composed a spike of spikelet as in wheat. Each spikelet may bear one to several flowers (florets) attached to a central stalk or rachilla.
Spikelet bears at the base a pair of glumes, the lower or other one called the first and the other or inner one called the second. Abone glumes and partly enclosed by them is a series of florets. Each floret at its base has a lemma or inferior palea and above a pale or superior palea. The lemma or inferior palea is the lower outer scale of the floret which in many species bears a long cylinder own or beared as an extention of the mid rip at the tip or beak. The superior palea often with two longitudinal ridges (keels or merves) stands between the lemma and rachilla. The presence of two merves conchide that it is formed by fushion of two bractioles. The essential organs of the flower lic between the tightly overlapping superior and inferior palea.
Flower: Sessile, bracteate, incomplete, bisexual (Bamboo, wheat, oat) or unisexual (Maize), Zygomorphic hypogynous.
Perianth: Sometimes 2 to 3 reduced membranous scales called lodicules lying on the anterior side below the stamns are regarded as rudimentary perianth.
Androcium: Normally there stamens (one to six in some speices e.g.: Bambusa and oryza (3+3_ filaments long free, anthers versatile, pollen grains dry.
Gynoecium: Tricarpellary syncarpous, though only one is functional uninlocular, single ovule, style short or more bearing long feathery stigmas. In maize the elongated stamens form long silken threads.
Fruit: Achenial,caryopsis. Seeds endospermic with single cotyledon.
+, ♀, P0 or 2 (lodicules), A3 or 3+3, G1.
(126) FIG 365 PAGE 479 AND FIG 366 PAGE 480 ANGIOSPERM BY G. L. CHOPRA
e.g.: Wheat (Triticum valgare), Corn (Zea rays) oats (Avena satwa), Rice (Oryza sativa), Sugarcane (Sacharum officinarum), Bamboo (Bambusa).
(1) Most plants i.e. cereal crops provide food forman.
(2) Dried stem and leaves of cereal crops yield toori which is used as fodder for cattle. Dried grass or hay is also used especially.
(3) Sugar, gur, shakkar are oblamied from sweet juice from stem of sugarcane.
(4) Paper is manufactured from grasses and bamboo.(5) Bamboos are used in building material. Tags: Biology , Botany
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