Family Poaceae (Graminae)

Systematic Position

Division: Angiosperms

Class: Monocotyledonae

Family: Poaceae (Graminae) (The grass family)

It is one of the largest families in monocots consisting of 620 genera and about 6000 species. Members are cosmopolitan in distribution. Around 900 species are present in India.

Characteristic Features

• Habit: Mainly herbs (annuals or perennials) or shrubs. Some are trees like (Bambusa, Dendrocalamus).

fig. 27.2 Bambusa and Dendrocalamus

• Root: Adventitious, fibrous, branched or stilt (as in maize).

• Stem: Underground rhizome in all perennial grasses, cylindrical, distinct nodes and internodes, herbaceous or woody.

• Leaves: Alternate, simple, extipulate, sessile, leaf base forming tubular sheath, sheath open, surrounding the internodes completely, hairy or rough, linear, parallel venation.

• Inflorescence: Compound spike, sessile or stalked. Each unit is called spikelet, may be a spike of spikelets (Triticum) or panicle of spikelets (Avena).

fig. 27.3 Avena and Triticum

• Flower: Bracteate, bracteolate, sessile, incomplete, bisexual or unisexual (Zea mays), zygomorphic, hypogynous, homochlamydeous.

fig. 27.4 Zea mays

• Perianth: Represented by membranous scales called lodicules, many (Ochlandra) or three or two or absent.

fig. 27.5

• Androecium: Stamens usually three, some times six (Bambusa) rarely one (species of Fistuca). Filaments long, anthers dithecous, versatile and linear.

• Gynoecium: Monocarpellary (presumed 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 cotyledon called scutellum, pressed against the endosperm

Floral diagram and formula

fig. 27.6 Floral diagram and formula of male flower

fig.27.7 Floral diagram and formula of female flower

Common Examples

Cereals

1. Triticum aestivum (wheat)

2. Zea mays (Maize)

3. Oryza sativa (Rice)

4. Hordeum vulgare (Barley)

5. Avena sativum (Oat)

fig. 27.8 Examples of Cereals

Millets

1. Sorghum vulgare (Jawar)

2. Pennisetum typhoides (Bajra)

fig. 27.9 Examples of Millets

Grasses

1. Cynodon dactylon (Dog grass)

2. Andropogon muricatus (Khas grass-oil yielding)

fig. 27.10 Examples of Grasses

Paper Grasses

1. Themeda gigantia (Kapoor grass)

2. Eucaliopsis binala (Bhabar grass)

fig. 27.11 Bhabar Grass

Other

1. Bambusa vulgans. (Bamboo plant of commercial ornamental importance)

2. Saccharum officinarum (Sugarcane plant)

fig. 27.12 Bamboo and Sugarcane Plants