Family: Poaceae (Graminae) (The Grass Family)
Lecture of: Sir Muhammad Ajaib
Department of Botany
G C University Lahore
Provided by: Taha Arooj
It is the largest family of monocots consisting 620 genera and about 10,000 species in 60 tribes. Members are cosmopolitan in distribution. Around 158 genera and 492 species in 26 tribes are reported in Pakistan.
Vegetative Characters:
Habit: Mainly herbs, (annuals or perennials) rarely shrubs sometimes with rhizomes and stolons. Some are trees like (Bambusa, Dendrocalamus)
Root: Adventitious, fibrous, branched or stilt (as in maize) .
Stem: Erect ascending or creeping, usually branched at the base. In perennial with sterile shoots and flowering stem (culms) mixed, in annual only the latter present; culms cylindrical, rarely flattened, jointed (distinct nodes and internodes) usually hollow at internodes. Underground rhizome in all perennial grasses, cylindrical.
Leaves: Solitary at nodes, sometimes crowded at the base of the stem, alternate and 2 rowed, consisting of sheath, ligule and blade, sheath encircling the stem with free, overlapping or connate, frequently swollen at base, ligule adaxial placed at the junction of sheath and blade, sometimes absent, blades usually long and narrow, rarely broad flat or rolled (terete), parallel nerved, extipulate, sessile.
Inflorescence: Compound spike, sessile or stalked. Each unit is called spikelet, may be a spike of spikelets (Triticum) or panicle of spikelets (Avena).
Flower: Bracteate, bracteolate, sessile, incomplete, bisexual or unisexual (Zea maze), zygomorphic, hypogynous, homochlamydeous.
Perianth: Represented by membranous scales called lodicules, many (Ochlandra) or three (Bambusa) or two (Oryza) or absent (Cenchrus).
Androecium: Stamens usually three, some times six (Bambusa) rarely one (species of Fistuca). Filaments long, Anthers dithecious, versatile or linear.
Gynoecium: Monocarpillary, (presumes to be three of which two are aborted), unilocular, single ovule on basal placentation, style short or absent, stigma bifid, ovary superior.
Fruit: A caryopsis with pericarp completely united with the seed coat, rarely a nut (Dendrocalamus) or a berry (Bambusa).
Seed: Endospermic with a single cotaledon called scutellum, pressed against the endosperm.
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Familiar Plants:
Cereals
- Triticum aestivum L. (Wheat)
- Zea mays L. (Maize, corn)
- Oryza sativa L. (Rice, Chawal)
- Hordeum vulgare L.(Barley, Jo)
- Avena sativum L. (Oat, Javi)
Millets
- Sorghum bicolor L. Moench. (Jawar)
- Pennisetum glaucum (L.) R. Br (Bajra)
Grasses
- Cynodon dactylon L. Pers. (common lawn grass, dog grass, Bermuda grass).
- Vetiveria zizanioides L. Nash (Khas grass-oil yielding).
Economic Importance
Grass Family in human terms, perhaps the most economically important including food production, medicinal, industry and lawns, etc.
Food Production
Agricultural grasses grown for their edible seeds are called cereals. Three cereals rice, wheat and maize (corn) provide more than half of all calories eaten by humans. Of all crops, 70% are grasses. Cereals constitute the major source of carbohydrate for humans and perhaps the major source of protein, and include rice in southern and eastern Asia, maize in Central and South America, and wheat and barley in Europe, northern Asia and the America.
Sugarcane is the major source of sugar production. Many other grasses are grown for forage and fodder for animal food, particularly for sheep and cattle.
Construction, Industrial Uses and Soil Reclamation
Grasses are used for construction such as Bamboo and arundo. Grass fiber can be used for making paper, and for biofuel production. Phragmites australis (common reed) is important in water treatment, wetland habitat preservation and land reclamation in the Old World.
Medicinal
Many grasses used for various treatments such as, Cynodon dactylon used for the treatment of urinary tract infections, prostatitis, syphilis, dysentery, diabetes. According to recent studies here is potential for Cynodon dactylon to become an alternative to current diabetes medications in the future. Similarly lemongrass (Cymbopogon Citratus DC.Stapf) commonly used in teas, soups, and curries. It is also suitable for poultry, fish, and seafood. Recently it is reported that lemongrass contains potent anticancerous properties.
Lawns
Grasses are the primary plants used in lawns. They are also provide an important means of erosion control (e.g. along roadsides), especially on sloping land. Grasses are still an important covering of playing surfaces in many sports, including football, tennis , golf, cricket, and softball/baseball.
