Asexual Reproduction in Organisms – Explanation and Types

Key Concepts

• Asexual Reproduction
• Binary Fission
• Fragmentation
• Sporogenesis
• Budding
• Vegetative Propagation

Introduction

Reproduction

The process of reproduction allows an organism to generate its young one.  

As a result, their species does not become extinct. A single parent or two parents participate in reproduction. 

We can divide reproduction into two categories based on this. 

Sexual reproduction: A process in which two parents take part in producing the young one. 

Asexual reproduction: When a single parent divides and reproduces its offspring by itself. 

Features of asexual reproduction: 

• One parent is involved. 
• There is no fertilization or gamete formation. 
• This reproduction procedure takes only a few minutes. 
• The creatures rapidly proliferate and flourish. 
• Genetically, the offspring are similar. 

Explanation

Both multicellular and unicellular creatures are capable of asexual reproduction. There will be no gamete fusion, and the number of chromosomes will remain the same. 

Except in some circumstances where a rare mutation may occur, it will inherit the same genes as the parent. 

The following are the types of asexual reproduction. 

• Binary Fission 
• Budding 
• Fragmentation 
• Vegetative propagation 
• Sporogenesis 
• Parthenogenesis 

Binary fission

The “fission” denotes “Division.” The parent cell splits into two during binary fission. Different species have directional and non-directional cell division tendencies. Binary fission occurs in amoeba and euglena. 

It is one of the most basic and simple asexual reproduction procedures. Each daughter cell has its nucleus, which is genetically identical to the parent cell. The cytoplasm splits as well, yielding two daughter cells of equal size. The process is repeated, and the offspring cells continue to divide and grow. 

Fragmentation

The parent organism fragments into pieces, each of which can evolve into a new organism.  

Fungi (such as yeasts and lichens), molds, cyanobacteria, sponges, sea stars, planarians, and many annelid worms.  

Animals’ asexual reproduction may also be unintentional.  

They may divide into fragments as a result of human activity, predation, and other environmental conditions. 

Budding

The creation of an extension (or bud) from an organism capable of growing into a new individual is referred to as budding reproduction.  

The offspring is genetically identical to the parent but is smaller. It may remain linked to the parent or eventually separate. Budding is the mode of reproduction in hydra, corals, echinoderm larvae, and some flatworms. 

Sporogenesis

Spore formation, also known as sporogenesis, is an asexual reproduction method that uses spores.  

Spores, derived from the words “spore” and “genesis,” which indicate “birth” or “origin,” are dormant reproductive cells that act as dispersal units comparable to seed.  

On the other hand, the spores are not seeds because they do not form an embryo from the fusing of male and female gametes.  

Spores have thick walls and are resistant to various adverse situations, such as high temperatures and low humidity. They germinate to produce new individuals when the conditions are right.  Asexual species that reproduce by spore production include vascular plants and fungus. 

Vegetative propagation

Plants reproduce asexually by vegetative propagation.  

When a new plant emerges from vegetative parts such as specialized stems, leaves, and roots, it is known as sprouting. 

They later expand and form their own root system. Pollination is not used in this method.  

New plants are instead grown from vegetative components with specialized reproductive functions.  

There are several types of vegetative propagation, divided into two categories:

• Natural
• Artificial

Runners (stolons), bulbs, tubers, corms, suckers (root shoots), and plantlets are all examples of natural means. 

Cutting, grafting, layering, budding, tissue culture, and other artificial ways are examples of artificial means. This method is carried out by humans. Horticulturists employ this method of reproduction to propagate economically significant plants.  

Rhizomes

Rhizomes are modified stems that grow horizontally over the ground’s surface or beneath them. 

Rhizomes are places where growth ingredients like proteins and carbohydrates are stored.  

Roots and shoots can emerge from rhizome segments and evolve into new plants as they grow. This way, some grasses, lilies, irises, and orchids reproduce.  

Ginger and turmeric are examples of edible plant rhizomes. 

Runners

Runners, also known as stolons, are like rhizomes in that they grow horizontally at or near the soil’s surface.  

They come from existing stems, unlike rhizomes. Runners establish roots from buds placed at nodes or tips as they expand. In runners, the intervals between nodes (internodes) are wider than in rhizomes. At nodes where shoots meet, new plants emerge. Examples include strawberry plants. 

Bulbs are the inflated, spherical sections of a stem that usually grow underground. The core branch of a new plant is found within these vegetative propagation organs.  

Bulbs are made up of layers of fleshy, scale-like leaves that surround a bud. These leaves serve as food storage and nutrition for the young plant. Onions, garlic, shallots, hyacinths, daffodils, lilies, and tulips are some of the plants that grow from bulbs. 

Tubers are vegetative organs that grow from the stems or roots of plants. Stem tubers develop from swelling rhizomes or runners that store nutrients. A tuber’s upper surface develops a new plant shoot system (stems and leaves), while its lower surface produces a root system. 

Stem tubers include things like potatoes and yams. Root tubers are made up of modified roots that can retain nutrients. These roots grow larger and may produce a new plant, including sweet potatoes and dahlias. 

Corms are underground stems that look like larger bulbs. These vegetative structures are often enveloped by papery leaves and store nutrients in fleshy, solid stem tissue. 

Corms are frequently confused with bulbs due to their physical appearance.  

The main distinction is that corms have solid tissue inside, while bulbs simply have layers of leaves.  

Corms contain buds that grow into new plant shoots and produce adventitious roots. Crocus, gladiolus, and taro are examples of plants that grow from corms. 

Plantlets are vegetative structures that form on the leaves of various plants.  

Meristem tissue along leaf margins produces these small, immature plants.  

Plantlets grow roots and drop from the leaves as they mature. After that, they take root in the soil and grow into new plants. Kalanchoe is an example of a plant that reproduces this way. Plantlets can also form on the runners of some plants, such as spider plants. 

Artificial vegetative propagation 

Cuttings

A cutting is a section of a mother plant that has been taken off and allowed to grow into a full plant.  

Before planting, a section of the stem is often treated with hormones to stimulate the formation of new roots. When placed straight into the soil, root cuttings with buds will occasionally develop new shoots. 

Budding and Grafting 

This procedure requires grafting or budding a stem portion (grafting) or a single bud (budding) onto the stem of a plant with roots. 

The scion is the stem piece or bud, while the rootstock is the plant with roots. 

Grafting is a popular method for cultivating fruit trees with multiple varieties of the same fruit species growing from the same stem. 

Layering 

The plant’s stem is bent and covered with earth in this method. Plant portions that have been covered in the soil produce adventitious roots. A layer is a term for the attached stem with growing roots. 

Tissue Culture

Tissue culture is a term used to describe the process of growing tissues. Plant cells from diverse areas of a plant are cultured in a laboratory to develop a new plant in this method.  

This method can be used to increase the number of rare and endangered plant species that cannot flourish in natural environments. 

Summary

• Asexual reproduction: When a single parent divides and reproduces its offspring by itself.
• Binary fission: The “fission” denotes “Division.” The parent cell splits into two during
  binary fission. Different species have directional and non-directional cell division
  tendencies. Binary fission occurs in amoeba and euglena.
• Fragmentation: The parent organism fragments into pieces, each of which can evolve into
  anew organism.
• Fungi (such as yeasts and lichens), molds, cyanobacteria, sponges, sea stars, planarians,
  and many annelid worms.
• Budding: The creation of an extension (or bud) from an organism capable of growing into
  anew person is referred to as budding reproduction.
• The offspring is genetically identical to the parent but is smaller.
• ‘Sporogenesis: Spore formation, also known as sporogenesis, is an asexual reproduction
  method that uses spores.
• Vegetative propagation: Plants reproduce asexually by vegetative propagation.
• There are several types of vegetative propagation, which can be divided into two
  categories: natural and artificial.
• Runners (stolons), bulbs, tubers, corms, suckers (root shoots), and plantlets are all
  examples of natural means.