15.4 Angiosperms : Monocotyledons

Monocotyledons are angiosperms (flowering plants) with an adventitious root system, parallel venation, trimerous symmetry of flowers and a single cotyledon in the embryo.

Sorghum, rice, wheat and corn arethe most commonly cultivated crops of the monocotyledons.

Sorghum vulgare : (Great millet)

Kingdom	-	Plantae
Sub-kingdom	-	Phanerogams
Division	-	Angiospermae
Class	-	Monocotyledones
Series	-	Glumaceae
Family	-	Gramineae
Genus	-	Sorghum
Species	-	Vulgare

The life cycle of sorghum is predominantly sporophytic and shows heteromorphic alternation of generations.

i) Plant body- External morphology (Fig. 15.21 A)

The sorghum plant is a diploid sporophyte. It is an herbaceous, tall annular plant which is sown during the monsoons. The plant is differentiated into roots, stem and leaves.

• The root system consists of two types of roots; primary and adventitious. The primary roots, called seminal roots develop first and penetrate vertically downwards in the soil. The adventitious roots develop from basal nodes. These are fibrous, branched, well developed and also function as stilt roots to support the tall plant.

• The stem is erect, solid, up to 10 feet tall and with distinct nodes and internodes. Few basal internodes are short. The internodes are smooth and cylindrical with a longitudinal furrow along one side.

• The leaves are simple, sessile and alternate. The leaf blade (lamina) is long and lanceolate with an acute apex. The surface is rough and hairy. Venation is multicostate and parallel, but with a very well developed mid-rib. Leaf base is long and sheathing. There is a short membranous ligule at the junction of the sheathing base and the lamina.

ii) Inflorescence: In sorghum, inflorescence is a terminal panicle (cluster) and develops as a more or less compact head. It consists of a profusely branched inflorescence axis (rachis). The ultimate branchlets of the rachis bear one to many pairs of spikelets. In each pair, one spikelet is sessile and perfect (bisexual) while the other is pedicelled and staminate. (Fig. 15.21B).

Table of Contents

15.0 - Introduction
15.1 Pteridophyta : General Account
15.2 Gymnosperms
15.3 Angiosperms : Dicotyledons
15.4 Angiosperms : Monocotyledons
15.5 Vascularization
15.6 Development of seed habit
15.7 Development of Flower and Fruit

Chapter 16