1. Diagnostic features
- New name: Poaceae
- Herbs with rounded stem and hollow internodes.
- Leaves simple, exstipulate alternate with sheathing leaf base, ligule usually present.
- Inflorescence compound spike.
- Flowers bisexual or unisexual, zygomorphic, subtended by glumes.
- Perianth minute, scaly called lodicules 2-3 in number.
- Stamens 3 with versatile anthers.
- Gynoecium monocarpellary with a single basal ovule, style 2-3 or absent, stigmas-2, lateral and feathery.
- Fruit caryopsis.
- Widely distributed throughout the world.
- Wide range of tolerance for climatic fluctuations.
- Therefore, grow on almost all sorts of habitat.
- Besides the normal region, they grow in arctic, Antarctic, deserts, high mountains regions and salty water.
3. Vegetative characters
- Mostly annual or perennial herbs.
- Rarely woody shrubs or tree-like reaching up to a height of 30 metre or more (Bambusa).
- Adventitious root system.
- Sometimes stilt roots arising from the basal nodes of stem in Zea mays.
- Aerial, erect, distinctly jointed mostly hollow.
- Sometimes solid, cylindrical, herbaceous or woody.
- In many species of grasses the stem is underground rhizome, or stolon, prostrate and creeping usually branched at the base.
- Caulin and ramal, simple, sessile, alternate, exstipulate, ligulate.
- Leaf sheath and leaf blade, ligule and auricles are present.
- Leaf sheath encircles the whole or a part of the internode.
- A membranous ligule margins fringed by hairs is present at the junction of the leaf sheath and leaf blade.
- Auricles are two claw-like appendages, present at the base of blade.
- The leaf blade is long, narrow, entire, acute having minute hairs on the margins.
- Venation multi-costate parallel.
4. Floral characters
- Spike or panicle of spikelets.
- The axis of inflorescence is called rachis and that of a spikelt, rachilla.
- Spikelet may be stalked or sessile.
- Each spikelet consists of one or more florets alternately on opposite sides of rachilla, subtended by two sterile or empty glumes.
- The florets are borne on the rachilla just above the second glume.
b) Flower or floret
- Bracteate, sessile or very rarely stalked.
- Complete, bisexual rarely unisexual, zygomorphic hypogynous.
- Each floret has two bracts at its base named lemma (Outer) and palea (inner) investing the essential organs (three stamens and single pistil with two feathery stigmas).
- Represented by 2-3 minute scales known as lodicules, placed within the lemma and palea, rarely absent.
- Stamens are usually 3 polyandrous.
- However the numbers of stamens vary in different species.
- In most grasses stamens are 3, in Leresia 6, in Sporobolus 2, in Uniola 1 and in Pariana 10-40.
- Filaments are long, anthers dithecous, basifixed or versatile, introse, dehiscing by longitudinal slit.
- Monocarpellary, sometimes 2 or 3 syncarpous are present.
- Ovary superior, unilocular, with one basal ovule.
- Stigmas two lateral and feathery.
- Caryopsis or rarely a berry.
- Endospermic, embryo variable in size.
h) General floral formula
- The family is of greater importance than any other family.
- The members are used in the following ways:
- Various cereals like Oryza sativa (rice), Triticum aestivum (wheat), Zea mays (maize), Hordeum vulgare (Barley), Avena sativa (oats), etc are used as foods.
- The straw of rice and wheat are used as stock feed for cattles.
- The whole aerial green part of several members is used as green fodder.
- Some important grasses used as fodder are: Cynodon, Agrostis, Dactyles, Imperata, Sorghum, Setaria, Poa, etc.
- Grains of wheat, rice, maize, etc. are used for manufacturing of various types of alcoholic beverages.
iv) Industrial use
- Maize and wheat are used for various purposes like adhesives, soaps, starch, plastics, linoleum, paper, etc.
- It is prepared from the stem of Saccharum officinarum (sugarcane).
vi) Jowar and Bajra
- Sorghum vulgare (Jowar), Pennisetum typhoides (Bajra or peal millet) are chiefly used for poultry and cattles.
- Also for preparing alcoholic beverages and diastase.
vii) Essential oils
- Oils obtained from several grasses like Cymbopogon caesius (ginger grass oil), C. citratus (lemon grass oil).
- Are used to make perfumes, medicines, creams, soaps, mosquito repellant, etc.
viii) Ornamental plants
- Several species of grasses are grown in the lawn for ornamental purposes like Axonopus affinis (Carpet grass), Coriaderia selloana (pampas grass), Cynodon dactylon (doobo grass), etc.
- It is a fast growing and multi-purposes plant.
- It is used in paper making.
- It is also used in several other works like house construction, baskets containers, fence and form an integral part of rural area.
Characteristics and economic importance of Gramineae (Grass family)