Monday, 14 November 2011

Vegetative propagation

This is the simplest method of reproduction found in plants. The vegetative parts of plant body such as roof, stem, leaf, etc., produce new members of the plant. You must have seen gardeners taking a cutting of the stem of a rose plant and putting it in the soil. Under suitable conditions the cutting grows into a new rose plant. In higher plants like orchids and ornamental plants, such vegetative propagation is common.

(a) Vegetative propagation by Roots:

In some plants like Dahlia, sweet potato, etc., adventitious roots become thick, swollen and tuberous due to storage of food. Adventitious buds are also present on them. When such roots, bearing these buds are planted in soil, new plants are produced as a result of vegetative propagation. On the tap roots of guava and shisham, adventitious buds are also present.

(b) Vegetative Propagation by Stems:

It is the common mode of vegetative reproduction. This is of two types:

(i) By sub-aerial stems:

Subaerial steams develop as lateral branches from the mother plant and give rise to a new individual after getting detached from the mother plant. In grasses, natural propagation occurs with the help of subaerial steam. The steam grows on the surface of the soil, breaks up and produces roots where it touches the ground to give rise to a new plant. Such types of subaerial stems are called runners. In Jasmine, a slender lateral branch which originates from the base of the steam is called stolon. Water hyacinth or Eichhornia propagates vegetative by offset.
It produces a tuft of leaves above and a cluster of small roots below. The subaerial stems found in mint and Chrysanthemum is known as suckers. It grows obliquely upwards and directly gives rise to a leaf shoot or a new plant.

(ii) By underground stems

In some plants the under-ground stem gets modified for storage of food. It lies in dormant and defoliated condition for some time and then gives rise to aerial shoots annually under favourable conditions. They are thick, fleshy and have a heavy food reserve in them. There are mainly four types of underground stem: rhizome, tuber, bulb, and corm.
Rhizome is a prostrate, creeping stem provided with distinct nodes and internodes (e.g., ginger, banana, turmeric and Canna). It possesses a bud in the axil of the scaly leaf. Some slender, adventitious roots are given off from its lower side. With the approach of the vegetative season, the auxiliary and terminal buds grow into the aerial shoots. The potato tuber has a number of eyes of buds on its external surface. The axial buds develop into aerial shoots when such a tuber is planted in the soil.
The bulb is vertical in direction and its terminal bud gives rise to the aerial shoot as in onion. Axiliary buds may also be produced in the axils of fleshy scales. These buds grow into aerial shoots under favourable conditions. Corm is the condensed form of rhizome which bears one or more buds in the axils of scale leaves. Some of these buds form daughter corms.
Take mint (pudina) stems. Cut the stem into pieces having at least one node in each piece. Now put these into soil. Give water in the soil. Observe the changes.

(c) Vegetative Propagation by Leaves:

The margins of succulent and fleshy leaves of Bryophyllum bear adventitious buds in their botches. When the leaves fall on the ground, the buds develop into small plants under favourable conditions. These plantlets can be easily separated to grow as independent plants. In walking ferns, when the tips of the older leaves come in contact with the damp soil, adventitious roots develop to give rise to a new plant.

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