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Subject : Botany Topic : Poaceae Descriptive and easily understandable. Important diagrams included. Written in point wise.
Typology: Study notes
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Class : Monocotyledons Series : Glumaceae Family : Poaceae
Mostly annual herbs with fistular stem. Leaves distichous with sheathing bases and ligule. Inflorescence unit is a spikelet. Perianth is reduced to lodicules or even absent. Anthers are versatile. Stigmas are feathery. Fruit is a caryopsis.
Habit :- The members are mostly annual (Oryza) or perennial (Saccharum) herbs. Sometimes they become woody and attain large size as in Bambusa, Dendrocalamus etc. Roots :- Fibrous and many plants possess rhizomes. The perennial grasses persist by means of rhizome formed by the lower internodes of the stem. Stem :- Stem of grasses, is called a culm, which is usually fistular or hollow (Bambusa). It is rarely solid as in Saccharum officinale. The stem is erect, prostrate or creeping.
Saccharum officinale Oryza sativa Bambusa bambos
Inflorescence :- Inflorescence is composed of spikelets arranged in racemes, panicles or spikes. Spikelet is the ultimate unit of the inflorescence in grasses, which is arranged variously on the rachis. Spikelets may have only bisexual flowers, or may have bisexual and male flowers or may have male and female flowers only. Each spikelet has very short or minute axis called rachilla on which bracts or glumes are arranged in two vertical rows. The lowest 2 glumes are sterile and bear nothing in their axils. The upper ones are fertile and each of them subtends a simple flower in its axil. This fertile bract or glume, which subtends the flower, is called the lemma.
Inflorescence :- The flower is enclosed by another membranous structure from above, the palea. It is considered to be bracteole. Thus the flower is enclosed by the lemma from below and by the palea from above. The fertile glumes (lemma) are closely similar to the sterile glumes (Eragrostis), or differ from them in shape, size and texture (Avena). Each floret is typically trimerous with great variation in the reduction of its parts.
Androecium :- of 3 each in Bambusa and Oryza. The stamens are numerous in Pariana. Anthers are dithecous, versatile and introrse, which open by a longitudinal slit. Gynoecium :- Gynoecium is variously interpreted as bi - or tricarpellary and syncarpous or monocarpellary and superior. But, it is always unilocular with a single ovule on basal placenta. Styles are usually 2 (rarely 1 or 3 or absent) & 3 in Bambusa. Stigmas are 2 and feathery.
Food :- This family consists of the most important food plants called cereals. They are the basic food for the human population. The important one include:- Wheat ( Triticum aestivum ), rice ( Oryza sativa ), maize ( Zea mays ), bajra ( Pennisetum typhoides ), jowar ( Sorghum vulgare ), barley ( Hordeum vulgare ), oats ( Avena sativa ), ragi ( Eleusine coracana ) etc. Saccharum officinale (Sugarcane) yields sugar.
Paper :- Bambusa and Dendrocalamus yield bamboos. Paper pulp is made out of bamboos. Medicinal :- Roots of Vetiveria zizanioides are medicinal and give a pleasant scent. Valuable perfumery oils are obtained from Cymbopogon citratus (lemon grass) and Andropogon odonatus (ginger grass). Ornamental :- Cynodon (Bermuda grass), Agrostis (florin grass) are all grown in lawns.
