8. Reproduction in Plants

Definition of asexual reproduction:

In this mode of reproduction, plants produce new plants without seeds.

Features:

1. This method does not involve the fusion of gametes.
2. Seeds are not produced in these type of plants.
3. It requires only one parent.
4. The new plant formed is identical to their parent.

Importance:

1. Rapid multiplication of plants.
2. New plants are exact copies of parent plant.
3. Important desirable traits can be preserved.
4. Better survival rate.

Let's study different modes of asexual reproduction.

Following are the types & sub-types of asexual reproduction in plants:

Let's understand each type in detail.

Vegetative Propagation

Definition:

It is a type of asexual reproduction, in which reproduction happens through vegetative parts.

New plants are produced from vegetative parts like: leaves, roots, stem & buds.

Advantages of vegetative propagation:

1. Reproduction by this method is faster than those produced from seeds.
2. It takes less time to grow & bear flowers & fruits.
3. The new plants are exact copies of the parent plant as they are produced from a single parent.
4. The plants are mostly disease resistant.

Vegetative Propagation takes place through stem, roots, leaves or buds.

To understand each mode of vegetative propagation, click here.

To remember:

• Vegetative propagation is a fast way to grow plants.
• Methods include cuttings, layering, and division.

Budding

1. This type of asexual reproduction is seen in yeast, a tiny microscopic organism.
2. A small bulb-like projection called bud, starts developing from the parent yeast cell.
3. This happens due to cell division.
4. The bud grows & gets detached from the parent cell to form a new yeast cell called the daughter cell.
5. This new yeast cell grows to produces more yeast cells.
6. Sometimes, another bud arises from the bud forming a chain of buds.
7. A large number of yeast cells are produced in very short time.

Features:

1. The daughter cells are identical copies of the parent cell.
2. When sufficient nutrients are available to the parent yeast cells, they multiply very quickly, usually within few hours.

Another example of asexual reproduction through budding is Hydra.

Fragmentation

1. This type of asexual reproduction takes place in algae*.
2. When algae gets water & nutrients, it breaks up into two or more fragments which grow into new individuals.
3. By this process of fragmentation, they cover a large area in a short period of time.

* Algae are slimy green patches found in ponds or stagnant water.

The following diagram shows fragmentation in spirogyra (a type of algae)

Spore Formation

1. In this type of asexual reproduction, there is a sac called sporangium.
2. It which consists of hundreds of spores. 
3. As the sporangium burst opens, the spores are released in the air.
4. As the spores are very light, they can be carried by wind, water or air to long distances. 
5. A spore germinates & develops into a new plant under favourable conditions.

Examples: 

1. Fungi on a bread piece grow from spores which are present in the air.
2. Mosses
3. Ferns 

About spores:

1. Spores are asexual reproductive bodies.
2. Each spore has a hard protective coat.
3. It protects the spore from adverse conditions like high temperature, low humidity.
4. Hence it can survive for a long time.
5. The process of forming spores is called sporogenesis.

Diagram of spores in fern plant

Fission:

1. It is a type of asexual reproduction in unicellular organisms.
2. Here, the parent cell splits into new identical daughter cells.
3. Fission means division into two or more parts.
4. It is of two types – binary & multiple.

Binary Fission:

1. In binary fission a single parent cell divides into two daughter cells.
2. Examples: bacteria, amoeba, paramecium, mitochondria, etc

Diagram:

Multiple fission:

1. In multiple fission, a single parent cell splits into many daughter cells.
2. Examples: plasmodium, sporozoans, etc.