Characteristics and economic importance of Gramineae (Grass family)

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.

2.Distribution

  • 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

a)Habit

  • Mostly annual or perennial herbs.
  • Rarely woody shrubs or tree-like reaching up to a height of 30 metre or more (Bambusa).

b)Root

  • Adventitious root system.
  • Sometimes stilt roots arising from the basal nodes of stem in Zea mays.

c)Stem

  • 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.

d)Leaves

  • 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 multicostate parallel.

4.Floral characters

a)Inflorescence

  • Spike or panicle of spikelets.
  • The axis of inflorescenceis 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).

c)Perianth

  • Represented by 2-3 minute scales known as lodicules, placed within the lemma and palea, rarely absent.

d)Androecium

  • 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.

e)Gynoecium

  • Monocarpellary, sometimes 2 or 3 syncarpous are present.
  • Ovary superior, unilocular, with one basal ovule.
  • Stigmas two lateral and feathery.

f)Fruit

  • Caryopsis or rarely a berry.

g)Seed

  • Endospermic, embryo variable in size.

h)General floral formula

 

Diagram of a typical lawn grass plant.                                       

 

Economic importance

  • The family is of greater importance than any other family.
  • The members are used in the following ways:
  1. Food
  • Various cereals like Oryza sativa (rice), Triticum aestivum (wheat), Zea mays (maize), Hordeum vulgare (Barley), Avena sativa (oats), etc are used as foods.
  1. Fodder
  • 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.
  1. Beverages
  • Grains of wheat, rice, maize, etc. are used for manufacturing of various types of alcoholic beverages.
  1. Industrial use
  • Maize and wheat are used for various purposes like adhesives, soaps, starch, plastics, linoleum, paper, etc.
  1. Sugar
  • It is prepared from the stem of Saccharum officinarum (sugarcane).
  1. Jowar and Bajra
  • Sorghum vulgare (Jowar), Pennisetum typhoides (Bajra or peal millet) are chiefly used for poultry and cattles and also for preparing alcoholic beverages and diastase.
  1. 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.
  1. 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.
  1. Bamboo
  • 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)

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