Vegetative Propagation: Natural and Artificial (Cutting, Layering and Grafting) Methods, Advantages and Disadvantages of Vegetative Propagation, Practice Problems and FAQs

Have you ever heard about the ‘Terror of Bengal’ ? No we are not talking about some terrorist organisation. We are talking about the water hyacinth plant or Eichhornia crassipes which is commonly referred to as the ‘Terror of Bengal’. Do you know why? It’s because this aquatic plant grows very rapidly in any water bodies and becomes the reason for the death of other aquatic plants and animals as it dangerously reduces the level of dissolved oxygen in water bodies. 

In fact you will be amazed to know that water hyacinth was introduced into the water bodies of Bengal as an exotic species for its beautiful flowers and shape of leaves. But it soon turned into a highly invasive species which not only spread through the water bodies of Bengal but also all throughout India. Do you know how this water weed managed to grow so rapidly?

It could do so because it reproduced by vegetatively propagating itself with the help of sub-aerial stem modifications known as offsets. If you are wondering what vegetative propagation means then keep reading the article to understand this process in detail.

Table of contents

• Introduction to vegetative propagation
• Natural vegetative propagation
• Artificial vegetative propagation
• Advantages 
• Practice problems
• FAQs

Introduction to vegetative propagation

Vegetative propagation is the formation of new plants from vegetative parts of the plant such as roots, stems and leaves. It is an asexual method of reproduction which involves a single parent and does not require the formation and fusion of gametes. Hence the offspring produced are morphologically and genetically identical to the parent plant. This process is very unique to plants and helps in reproduction of plants without the formation of flowers or seeds.

Types of vegetative propagation

Vegetative propagation can occur naturally in plants in which a vegetative part of the plant detaches from the body of a mother plant and develops into a new plant. However, a number of techniques have also been developed by farmers and gardeners to propagate useful plants vegetatively for quicker multiplication and obtaining a uniform progeny.

Natural Vegetative Propagation

Natural vegetative propagation occurs via vegetative parts of a plant such as stems, roots and leaves which naturally detach from the parent plant and develop into individual plants under favourable environmental conditions. The vegetative parts giving rise to new plants are known as vegetative propagules. Let us discuss how the different vegetative parts of a plant help in vegetative propagation

Roots

Tap roots or adventitious roots of plants can give rise to adventitious buds (buds growing from places other than apex of a shoot or axil of a leaf). These buds can grow into independent plants and help in vegetative propagation. Tap roots taking part in vegetative propagation are found in Dalbergia (Sheesham), Populus (poplar), etc. Fleshy adventitious roots which help in vegetative propagation are seen in sweet potato, Dahlia, tapioca, etc.

Stem

Different types of underground and sub-aerial modifications of stems can take part in vegetative propagation.

Underground stem 

All underground modifications of the stem are capable of vegetative propagation. These include rhizomes, tubers, bulbs and corms.

Rhizome

Rhizome is a fleshy and horizontal underground stem modified to store food. It has prominent nodes and internodes. Nodes possess axillary buds covered by scaly leaves. Adventitious roots develop at the nodes. Examples: Banana, ginger, turmeric, etc.

Tuber

Tubers are swollen modified underground stems which store food. These have slender internodes and a stouter form compared to rhizomes and do not possess adventitious roots. They have depressions known as eyes which bear axillary buds covered with scaly leaves. Examples: Potato.

Bulb

Bulb is an underground condensed disc-like stem which possesses adventitious roots at its base. The stem has overlapping leaves or leaf bases known as scales and internal apical buds. The scales may be scaly or fleshy and tunicated. Examples: Onion, garlic, tulip.

Corm

Corm is a vertically oriented unbranched swollen underground stem which bears circular nodes. The nodes bear many buds in axils of scale leaves which grow into aerial shoots. New corms are formed when food gets stored at the base of the shoots. Examples: Amorphophallus (zaminkand), Colocasia (arbi).

Sub-aerial stem

There are four types of sub-aerial stem modifications which help in vegetative propagation. These include - runners, suckers, stolons and offsets.

Runner

Runners arise from the base of an aerial shoot known as crown. The branches of runners creep horizontally on the ground and have long and thin internodes. The nodes develop adventitious roots. The axils of scale leaves present at the nodes give rise to aerial branches. The daughter plants propagate in a similar manner upon separation from the parent plant. Example: Strawberry, grass.

Stolon

Stolons are special arched sub-aerial prostrate branches which grow from the base of an aerial shoot and bear nodes and internodes. They bend downwards to touch the ground after growing aerially for some time. At the point of contact with the gound, the terminal bud gives rise to a new shoot and adventitious roots. Example: Mint.

Offset: Runner of aquatic plants

Offsets are one internode long horizontal branches found in some aquatic plants. The axil of the lower leaves of the main shoot give rise to offsets. The nodes of offsets bear a rosette of leaves above and a cluster of roots below. Each branch can grow into a new plant upon detaching from the parent plant. Examples: Pistia, Eichhornia.

Sucker

Lateral branches arising from the underground axillary bud of an aerial shoot are known as suckers. The lateral branches grow obliquely under the ground for some distance before rising up from the ground. Axillary buds at the nodes of suckers give rise to new plants. Examples: Chrysanthemum.

Aerial shoot

Buds present on certain aerial stems can directly give rise to new plants when stem segments fall on the soil, e.g., phylloclades of Opuntia. 

Leaves

Leaves of some plants develop adventitious buds for vegetative propagation. In Bryophyllum the adventitious buds grow on the margins of the leaves and as the leaf detaches from the parent plant and falls on the soil, the buds develop into independent plants.

Bulbils

Bulbils are fleshy axillary buds in plants such as Dioscorea and lily or modified flowers in Agave that can develop into new plants.

Turions

These are fleshy buds which develop in aquatic plants for propagation as well as perennation (ability to survive from one germinating season to the next), e.g., Utricularia.

Artificial Vegetative Propagation

Artificial methods of vegetative propagation involve man-made special techniques which are used to develop a new independent plant from the vegetative part of a plant. This method is used to propagate desired varieties of plants based on human requirements. The commonly used methods of vegetative propagation are cutting, layering, grafting and tissue culture or micropropagation.

Cutting

Cutting is a process in which segments of root, stem or leaves are planted into the soil and sometimes treated with growth hormones such as NAA, IBA, etc to promote the development of roots (rooting). As adventitious roots develop, A new plant develops from the cut part of the plant.

Cutting can be of three types -

Stem cutting

A piece of stem from the parent plant, including at least one leaf node and intact buds is first treated with root inducing hormones and then planted into the soil in their natural polarised position. A new shoot develops from the buds and roots develop at the base of the cut stem. This method is used to propagate a number of plants such as rose, china rose, Bougainvillaea, etc.

Root cutting

A root cutting of 20-30cm long is buried below the surface of the soil, and new shoots are to be developed. This method of propagation is used for lemon, fig, etc.

Leaf-cutting

Sansevieria or snake plant is vegetatively propagated using leaf cuttings. A leaf is cut transversely into two or more pieces and the cuttings are vertically planted into the soil. Root promoting hormones might be added to induce the development of adventitious roots from the base.

Layering

In this technique a soft one year old shoot is first induced to develop roots and then cut off to form a new plant. Layering is more complicated than cutting, but it has the benefit that the roots and shoots both receive a good amount of water and nutrients while forming roots.

A middle part of a shoot is defoliated (leaves are removed) and given a small injury in the form of ringing (removal of bark in a narrow ring like form), notching (a narrow V shaped cut) or tongueing (tongue-like cut). It is then buried into the soil with the apical part remaining above the ground in a vertical position. The injured buried part of the stem is known as a layer. As the roots develop in the injured region, the layer is cut off and planted in the soil to develop into an independent plant.

For example - Rhododendron, jasmine ,guava, raisins, tomatoes ,black and purple raspberries with blackberries trailing, strawberries, roots of plum, magnolia, peach, etc are propagated artificially using this technique.

Grafting

Grafting is a technique of forming a superior composite plant by joining the shoot system of a superior high yielding variety with the stronger and efficient root system of generally a local variety. This process can be carried out only in those plants which possess vascular cambium. The selected shoot is called a scion and the selected root system is called a stock. 

The shoot system of the stock is cut around 10-30 cm above the base of the root. All the buds and leaves are removed from this part. Complementary cuts are made in the stock and the scion and the scion is inserted over the stock in such a way that their cambia align together. The union is covered by a grafting wax and bandaged. Grafting is successful if the scion starts bearing leaves and branches.

Mango, guava, peach, apple, etc are some plants that are commonly propagated by grafting.

Tissue culture

Tissue culture or micropropagation is the process of in vitro culturing of a large number of plantlets from different plant parts under aseptic and controlled conditions of a laboratory. These plantlets can then be transferred into fields.

Advantages of Vegetative Propagation

• Vegetative reproduction has several benefits, primarily because the developed offspring represent copies of their parent plants. If a plant has positive features, the genetic information can be passed on to its offspring.
• Commercial growers may profit by cloning such plants in order to ensure their crops remain compatible financially.
• Vegetative propagation often helps plants in the development of sex organs such as flowers and eventual seeds and fruit to avoid costly and complicated processes.
• It increases the chances of a plant reaching maturity effectively in nature and saves growers a great deal of time and money on a commercial basis as it permits a quicker overturn.
• Vegetative reproduction offers scientific opportunities in several biological fields

Disadvantages of vegetative reproduction

• This process reduces species diversity as offspring are clones of their parents.
• If the parent plant has some genetic deformity or defect, then that is passed on to the offspring. 

Practice problems

Q 1. Which is wrongly matched?

a. Agave — bulbils
b. Strawberry — runner
c. Water Hyacinth — stolon
d. Chrysanthemum — sucker
Answer: Vegetative propagation in water hyacinth occurs via a modified sub-aerial stem known as offset. Offsets are one internode long horizontal branches found in some aquatic plants. The axil of the lower leaves of the main shoot give rise to offsets. The nodes of offsets bear a rosette of leaves above and a cluster of roots below. Each branch can grow into a new plant upon detaching from the parent plant. Hence option c is correct.

Q 2. Which of the following is vegetatively propagated by roots?

a. Ginger 
b. Chrysanthemum
c. Sweet Potato 
d. Potato
Answer: Fleshy adventitious roots of sweet potato give rise to adventitious buds that can develop into a new plant on coming in contact with moist soil. Hence ,option c is correct.

Q 3. In potato, sugarcane, banana, ginger and Dahlia, the new plantlets arise from

a. the nodes of modified stems
b. the nodes of modified roots
c. the internodes of modified stems
d. leaf buds
Answer: Nodes are the regions on the stem from where a leaf or new branch arises. In potato, sugarcane, banana, ginger and Dahlia, the new plantlets arise from the adventitious buds growing at the nodes present in the modified stem. Hence, option a is correct.

Q 4. Which of the following plants propagates through leaf buds? 

a. Cannabis 
b. Chrysanthemum 
c. Bryophyllum 
d. Brassica
Answer: Bryophyllum possesses adventitious buds on the margin of the leaves which can develop into new plants when the leaf falls on the soil. Thus, the correct option is c.

FAQs

Q 1. Which is the best time of the day to propagate cuttings?
Answer: Cuttings should be propagated during early morning of the day when the plant parts remain fully turgid due to minimum transpiration.

Q 2. Are stolons and runners the same?
Answer: Both stolons and runners are subaerial stem modifications that arise from the base of an aerial shoot but stolons are different from runners as they develop just under the ground unlike runners which develop above the ground.

Q 3. Can grafting be carried out in monocots?
Answer: Grafting is a technique of forming a superior composite plant by joining the shoot system of a superior high yielding variety with the stronger and efficient root system of generally a local variety. 

It disrupts the vascular system and require regeneration of the vascular system to maintain proper transportation of food and water in plants. Monocots do not possess vascular cambium which is a lateral meristematic tissue that can divide and produce secondary xylem and secondary phloem in plants. In the absence of vascular cambium, regeneration of tissues in monocots is impossible which in turn makes grafting impossible.

Q 4. Does grafting give rise to genetically modified plants?
Answer: According to recent studies, contrary to popular belief that grafting is an asexual mode of plant propagation, it has been documented that grafting can bring about genetic variations in plants. It enables exchanges of both RNA and DNA molecules between the the stock and the scion, thus allowing changes in genetic composition.

Youtube link: https://www.youtube.com/watch?v=A2z2yLYbam0 

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