Types of Vegetative Propagation

Vegetative propagation or vegetative reproduction is the growth and development of a plant by asexual means. This development occurs through the fragmentation and regeneration of specialized vegetative plant parts. Many plants that reproduce asexually are also capable of sexual propagation.

The Process of Vegetative Propagation

Vegetative reproduction involves vegetative or non-sexual plant structures, whereas sexual propagation is accomplished through gamete production and subsequent fertilization. In non-vascular plants such as mosses and liverworts, vegetative reproductive structures include gemmae and spores. In vascular plants, vegetative reproductive structures include roots, stems, and leaves.

Vegetative propagation is made possible by meristem tissue, commonly found within stems and leaves as well as the tips of roots, that contains undifferentiated cells. These cells actively divide by mitosis to allow widespread and rapid primary plant growth. Specialized, permanent plant tissue systems also originate from meristem tissue. It is the ability of meristem tissue to continually divide that allows for plant regeneration required by vegetative propagation.

Advantages and Disadvantages

Because vegetative propagation is a form of asexual reproduction, plants produced through this system are genetic clones of a parent plant. This uniformity has advantages and disadvantages.

One advantage of vegetative propagation is that plants with favorable traits are repeatedly reproduced. Commercial crop growers can employ artificial vegetative propagation techniques to ensure advantageous qualities in their crops.

A major disadvantage, however, of vegetative propagation is that it does not allow for any degree of genetic variation. Plants that are genetically identical are all susceptible to the same viruses and diseases and crops produced through this method are, therefore, easily wiped out.

Types of Vegetative Propagation

Vegetative propagation may be accomplished by artificial or natural means. Though both methods involve the development of a plant from parts of a single mature part, the way that each is carried out looks very different.

Artificial Vegetative Propagation

Artificial vegetative propagation is a type of plant reproduction that involves human intervention. The most common types of artificial vegetative reproductive techniques include cutting, layering, grafting, suckering, and tissue culturing. These methods are employed by many farmers and horticulturists to produce healthier crops with more desirable qualities.

• Cutting: A part of a plant, typically a stem or leaf, is cut off and planted. Adventitious roots develop from the cuttings and a new plant forms. Cuttings are sometimes treated with hormones before being planted to induce root development.
• Grafting: In grafting, a desired cutting or scion is attached to the stem of another plant that remains rooted in the ground. The tissue systems of the cutting become grafted into or integrated with the tissue systems of the base plant over time.
• Layering: This method involves bending plant branches or stems so that they touch the ground. The portions of branches or stems in contact with the ground are then covered with soil. Adventitious roots or roots that extend from structures other than plant roots develop in the parts covered by soil and the attached shoot (branch or stem) with new roots is known as a layer. This type of layering also occurs naturally. In another technique called air layering, branches are scraped and covered with plastic to reduce moisture loss. New roots develop where the branches were scraped and the branches are removed from the tree and planted.
• Suckering: Suckers attach to a parent plant and form a dense, compact mat. Since too many suckers can lead to smaller crop size, excess numbers are pruned. Mature suckers are cut away from a parent plant and transplanted to a new area where they sprout new plants. Suckering has the dual purpose of growing new shoots and removing nutrient-sucking buds that prohibit a main plant from growing.
• Tissue Culture: This technique involves the culturing of plant cells that may be taken from different parts of a parent plant. The tissue is placed in a sterilized container and nurtured in a special medium until a mass of cells known as a callus is formed. The callus is then cultured in a hormone-laden medium and eventually develops into plantlets. When planted, these mature into fully grown plants.

Natural Vegetative Propagation

Natural vegetative propagation happens when plants grow and develop naturally without human intervention. An important ability that is key to enabling natural vegetative propagation in plants is the ability to develop adventitious roots.

Through the formation of adventitious roots, new plants may sprout from stems, roots, or leaves of a parent plant. Modified stems are most often the source of vegetative plant propagation. Vegetative plant structures that arise from plant stems include rhizomes, runners, bulbs, tubers, and corms. Tubers can also stretch from roots. Plantlets emerge from plant leaves.

Plant Structures That Enable Natural Vegetative Propagation