Types of asexual reproduction - fragmentation, vegetative propagation and artificial vegetative propagation.
Fragmentation
Definition
Fragmentation is a type of asexual reproduction in which the parent organism breaks into two or more pieces (fragments), and each fragment develops into a complete new organism.
The new organisms are genetically identical to the parent (except for rare mutations) and are therefore clones.
Fragmentation occurs in some algae, fungi, and simple animals.
How Fragmentation Occurs
Step 1: The parent organism grows.
The organism grows until it reaches a certain size.
Step 2: The parent breaks into fragments.
The body splits or breaks into two or more pieces. This may happen naturally as the organism grows or because of physical forces, such as water movement or damage.
Each fragment contains living cells with a complete copy of the organism’s DNA.
Step 3: The fragments grow.
Cells within each fragment divide repeatedly by mitosis, replacing the missing parts of the organism.
Step 4: New organisms are formed.
Each fragment develops into a complete organism capable of living independently.
Because the new organisms develop without fertilization, they are genetically identical to the parent (except for rare mutations) and are therefore clones.
Vegetative Propagation (Natural)
Definition
Vegetative propagation is a type of natural asexual reproduction in which a new plant grows from a vegetative part of the parent plant instead of from a seed.
In potatoes, the new plant develops from a tuber, which is a modified underground stem containing buds.
What is a Potato Tuber?
Although we eat potatoes as vegetables, a potato is actually a modified underground stem called a tuber.
Its functions are:
To store food (starch) for the plant.
To enable asexual reproduction through vegetative propagation.
On the surface of the tuber are small spots called eyes. Each eye contains a bud that can grow into a new plant.
How Vegetative Propagation Occurs
Step 1: The tuber stores food.
The tuber stores starch produced by the parent plant during photosynthesis. This starch provides the energy needed for future growth.
Step 2: The buds begin to grow.
When conditions are suitable (enough water, oxygen, and a suitable temperature), the buds begin to sprout as cells divide by mitosis.
Step 3: Roots and shoots develop.
Shoots grow upward towards the soil surface to reach sunlight, while roots grow downward into the soil to absorb water and minerals.
The young plant uses the stored starch in the tuber because it cannot yet produce enough food by photosynthesis.
Step 4: The new plant becomes independent.
Once leaves have developed, the new plant carries out photosynthesis and makes its own food.
As the stored starch is used up, the parent tuber gradually shrivels.
Artificial Vegetative Propagation
Definition
Artificial vegetative propagation is the production of new plants from the vegetative parts of a parent plant using methods carried out by humans rather than occurring naturally.
The new plants are genetically identical to the parent plant and are therefore clones.
Why Do Humans Use It?
Artificial vegetative propagation allows farmers and gardeners to produce many plants with the same desirable characteristics as the parent plant, such as:
Sweet fruits.
Large flowers.
High crop yield.
Disease resistance.
Because the new plants are clones, they retain these desirable characteristics.
Methods of Artificial Vegetative Propagation
1. Cuttings
A healthy stem, leaf, or root is cut from the parent plant and planted in moist soil or water.
Roots develop first, followed by shoots and leaves.
The cutting eventually grows into an independent plant.
2. Grafting
A stem or bud from one plant (the scion) is joined to another plant (the rootstock).
The two parts grow together as one plant.
This combines useful characteristics, such as:
Strong roots from the rootstock.
High-quality fruits or flowers from the scion.
3. Tissue Culture (Micropropagation)
A small piece of plant tissue containing living cells is taken from a healthy parent plant.
The tissue is placed in a sterile container containing nutrients and plant hormones.
The cells divide by mitosis to produce many identical plantlets.
Each plantlet can then be planted in soil and grown into a mature plant.
Why Is It Called Artificial Vegetative Propagation?
Like natural vegetative propagation, new plants develop from vegetative parts of the parent plant rather than from seeds.
The difference is that natural vegetative propagation occurs without human involvement, whereas artificial vegetative propagation uses techniques carried out by humans to produce new plants.
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