Asexual Reproduction in Plants

Vegetative Propagation is a plant’s ability to produce new plants without reproducing sexually, but simply as an outgrowth of old vegetative structures. Vegetative Propagation may occur naturally but can also be stimulated by human influence.

Natural Processes of Vegetative Propagation

Most times, asexual reproduction in plants occurs naturally, without human influence. New plants may be formed from rhizomes, corms, stem tubers and bulbs.

Rhizomes

Rhizomes are horizontal underground stems. This is made evident by their physical properties which greatly reflect the properties of a stem. For example, there are scale leaves or scars where leaves were once attached to the stem and buds grow in the axils of these leaves. It is from these bids that the shoots of the new plant develop and grow. Adventitious roots form from the nodes of the rhizome. There newly developed shoots and adventitious roots form a newly produced plant. Examples of rhizomes are ginger and devil’s grass.

Corms

Corms are short, swollen underground stems which look like short, upright rhizomes. Like most stems, the corm has a bud(s), which serves as its point of growth. In the case of the corm, the bud(s) can be found at the top of the corm and it is from this bud that a shoot begins to grow, eventually forming a new plant. Examples of corms include dasheen and garlic.

Stem Tubers

Stem Tubers are the swollen ends of slender rhizomes. New plants develop from buds and roots growing at the nodes in the stem tubers. Buds grow into shoots and leaves at the top and on the side of tubers. Roots grow at the bottom. Examples of stems tubers are Irish Potatoes and yams.

Bulbs

Bulbs are underground vertical shoots which have modified leaves. A modified stem forms the base of the bulb and it is from this stem that the new plant emerges. Roots emerge from under the base of the bulb. Shoots and leaves emerge from the top of the base. This root and shoot system forms a new plant. Example of bulbs include onion and tulip.

Artificial Processes of Vegetative Propagation

Gardeners have learned to use the asexual reproduction of plants to their advantage and are now using artificial methods of vegetative propagation to increase the stock of a plant. Two ways in which this is done is via cuttings and grafting. These methods are considered to be artificial as they do not occur naturally.

Cuttings

Cuttings are the most common method of artificial vegetative propagation used as many plants can be produced from just one parent plant. In this method, cuttings may be taken mainly from the stems and roots of the parent plant. These cuttings must include a meristematic region from which growth (via mitosis) can occur. The cuttings, when placed in a suitable, for example, moist soil and under the right conditions (sufficient nutrients, water and sunlight), develop roots and shoots. The roots and shoots grow and develop into a plant identical to the parent plant from which the cuttings were taken.

This process is used to provide many plants from one single plant, each plant being exactly the same. It is beneficial to agricultural farmer as it is a quick, easy method to produce a vast number of crops. One such example where artificial vegetative propagation has been very beneficial is on a sugar cane plantation. The asexual reproduction of plants via cuttings is much faster and produces much more than sexual reproduction would.

Grafting

Trees are grafted when the growth of more of a plant with good flower or fruit is desired but that plant is not wanted grown on its own root system. This may be because the original root system of the plant may be too weak, hindering the growth of the plant, or too strong. Trees such as citrus, mango and apple are often grafted onto root stocks.

Grafting occurs this way; Piece of stem is cut from the plant which is being propagated, that is the plant which is being grafted onto root stock. This piece of stem is inserted into the root stock and bound tightly in place. After a while, after the vascular bundles of the stem and the root stocks have been connected to each other, the stem and root stock begin to grow together. The new plant has all the features of its parent plant but its size is controlled by the root stock which it has been grafted onto.

In short, plants can reproduce asexually via vegetative propagation. When this occurs spontaneously, that is without human influence, it is called natural vegetative propagation. Processes of natural vegetative propagation include the formation of new plants via rhizomes, corms, stem tubers and bulbs among many others. Artificial Vegetative propagation is brought about by human and methods of artificial vegetative propagation do not occur naturally. These include cuttings and grafting.