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 multi-costate parallel.

4. Floral characters

a)Inflorescence

• 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).

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

Economic importance

• The family is of greater importance than any other family.
• The members are used in the following ways:

i) Food

• Various cereals like Oryza sativa (rice), Triticum aestivum (wheat), Zea mays (maize), Hordeum vulgare (Barley), Avena sativa (oats), etc are used as foods.

ii) 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.

iii) Beverages

• 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.

v) Sugar

• 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.

ix) 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.

References: 

i) https://agriculturistmusa.com/cucurbitaceae-gramineae-solanaceae/

ii) https://onlinesciencenotes.com/characteristic-features-economic-importance-family-gramineae/

Characteristics and economic importance of Gramineae (Grass family)