Onion

Morphology and Taxonomy of Onion

by

M A Baset Mia

Common name: Onion

Scientific name: Allium cepa L.

Local/Bangla name: ‘Piaj’

Taxonomic Position According to Cronquist (1988)

Kingdom:       : Plantae

Division:         : Magnoliophyta

Class:              : Liliopsida

Subclass:        : Liliidae

Order:            : Amaryllidales

Family:          :  Liliaceae

Genus:           : Allium

Species:          : A. cepa 

Botanical Description of Onion:

Habit: Annual herb.

Root: Fibrous root system.

Stem:Stem underground and modified into a small disc, generally known as bulb.

Fig. Onion bulb

Leaf: Radical concentrically arranged, exstipulate, sessile, cylindrical, fistular, leaf bases fleshy, parallel venation. Leaves are arranged on the disc-like stem in concentric circles.

Inflorescence: Terminal raceme umbel.

Flower: Pedicellate, complete, bisexual. Perianth 6, stamens 6, inserted at the base of the perianth lobes, filaments free, somewhat dilated below, anthers oblong, stigma one.

Fruit: Fruit a membranous capsule.

Seed: Seeds compressed, black.

Chromosome number:2n=16

Fig. Fruits of onion

Fig. Inflorescence of onion

Fig. Onion seeds

blade partly decurrent upon it in the upper portion. The lamina is lanceolate or narrowly elliptical or obovate, the apex is shortly or broadly bluntly acuminate and the base is cuneate.

Flower: The inflorescence is a terminal, corymbose, trichotomous panicle, shortly pedunculate and branched from the base. The flower is hermaphrodite with a fleshy hypanthium which is surmounted by the sepals. The four calyx lobes are fleshy, triangular, slightly incurved. The four petals are imbricate, tinged red, rounded. The stamens are very numerous, appearing grouped in four masses. The anthers are pale-yellow, ovate, opening longitudinally wit small pale brown in colour, The style is very stout, swollen at the base, pale green and gland-dotted.

Fruits: The fruits called mother of  cloves are oblong, fleshy, drupes, usually shortly tapering at each end reddish purple in color. They are surmounted by  the four enlarged fleshy calyx lobes. There is a thin fleshy pericarp about 2-3 mm thick.

Economic Importance

• Used as spices
• Used as vegetable
• Has medicinal  virtue

Table 1. Onion variety developed by Spices Research Center (SRC), BARI, Joydebpur and Bangladesh Institute of Nuclear Agriculture (BINA), Mymensingh, Bangladesh