Reproduction in Plants: Modes (Asexual and Sexual), Advantages and Process

Reproduction in Plants Reproduction is an important life process of living organisms. It is a process by which living organisms produce their offspring. It is also called the production of new organisms from the existing organisms of the same species. Reproduction ensures the stability of the ecosystem and ensures the continuation of life on earth. In this article, we will discuss reproduction in plants. 

Check out: How are water and minerals transported in plants?

Keyterms: Reproduction, living organisms, species, plants, asexual and sexual reproduction, seeds, gametes, fusion, mitosis, meiosis, Cell division

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Reproduction in Plants

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Reproduction in Plants can be carried out in two mode:

1. Asexual Reproduction
2. Sexual Reproduction 

Here is the difference between asexual and sexual reproduction. 

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Asexual Reproduction in Plants

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In asexual reproduction, identical new plants are formed from a single parent without the formation of seeds. Methods of asexual reproduction are –

Vegetative Propagation 

In this method, new plants are produced from the vegetative parts of the plant like roots, stems, leaves or buds.

Natural Methods of Vegetative Propagation: 

Roots: In some plants, the roots get modified into tubers. The tuberous roots become swollen with stored food and remain underground. They also have adventitious buds which grow into new plants. Ex- sweet potato.

Roots

Stems: New plants can also be formed from the nodes of underground or subaerial stems.

Modifications in stems –

Bulb – It is a disc-shaped underground modification of the stem. Example – Onion, Garlic, etc.

Bulb

Tuber – This underground stem modification occurs in the plants which have eyes. The eyes contain buds which grow into news shoots. Example – Potato

Tuber

Rhizome – These underground stem modifications occur in the plants which have nodes. Example – Ginger

Rhizome

Runner – These are subaerial stem modifications where horizontal stems grow parallel to the ground. The stem has nodes which form buds and grow into new shoots. Example – Strawberry

Runner

Leaves: In many plants, adventitious buds grow along the leaf margins. When the buds fall on the ground they develop into new plants. Example – Bryophyllum, Begonia

Leaves

Artificial Methods of Vegetative Propagation

Some artificial methods are often used to produce new and unique plants.

• Cutting – A healthy young branch of a plant having leaf buds is cut and planted in moist soil. The cutting grows roots and develops into a new plant. Example – Rose, Chrysanthemum

Cutting

• Layering – A branch of a plant is bent to touch the ground. It is layered with moist soil. Roots start developing from the covered plant. Then, the branch is cut off from the main plant. Example – Jasmine, Bougainvillea

Layering

• Grafting – Cutting of one plant (with buds) called the scion is kept over and tied with the cut stem of another part called the stock which is rooted in the soil. The tissues join together after sometime and form a new plant. Example – Mango, Rose, Citrus Plant

Grafting

Tissue Culture / Micropropagation

A small piece of tissue, called explant, is cut off from the growing tip of the plant and is grown under laboratory conditions. The cells divide rapidly to form a cell-mass called callus. Then, the callus divides and differentiates into different parts of the plant. This method is used to cultivate disease free, endangered and rare plant species. Example – Orchids

Tissue Culture / Micropropagation

Budding 

In some plants, small outgrowths called buds develop on the body. The bud grows and then detaches from the parent plant and forms a new individual. Example – Yeast, Hydra

Budding in Hydra

Fragmentation

Some plants simply break into two or more fragments and each fragment grows into a new individual. Example – Spirogyra

Fragmentation

Spore formation 

Plants like fungi reproduce by forming spores under unfavorable conditions. Spores are thick-walled, resistant asexual reproductive bodies. They germinate under favorable conditions and form new plants. Example – Bread mould, Mushroom

Spore Formation

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Advantages of Asexual Reproduction in Plants

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1. The new plants produced are exact copies of the parent plant with no genetic variability. Such plants have better chances of survival.
2. Less attention and care is required to the plants produced by asexual reproduction.
3. A large number of new plants can be produced in a short period of time.
4. Pollination and seed dispersal are not needed.
5. Many seedless varieties of plants have been developed through this process. Example – Grapes, Banana and Pineapple.

Read More: Parts of a Seed

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Sexual Reproduction in Plants 

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Sexual Reproduction involves two parents and formation of gametes. In plants, sexual reproduction occurs in angiosperms. Angiosperms are plants that produce flowers and bear their fruits in seeds. Their reproductive parts are present in the flower.

The flower has four parts – sepal, petal, stamen and carpel. Sepals and Petals are the non-reproductive parts whereas Stamens and Carpels are the reproductive parts of the plant. 

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Reproductive Parts of Flowers

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Reproductive Parts of Flowers

Androecium

Androecium is the male reproductive part of the plant.

• It consists of Stamens which is the male reproductive organ.
• Each stamen is made up of a stalk or filament which supports an anther.
• The anther is a lobed structure. Most plants have bilobed anthers.
• Each anther lobe has two chambers called the pollen sacs. These pollen sacs produce the pollen grains or microspores.
• Pollen grains are yellowish powder like microscopic structures that carry the male reproductive cell of the plant.
• The male reproductive cell is also called the male germ-cell or the male gamete.
• A sterile stamen is known as a staminode.

Gynoecium

Gynoecium is the female reproductive part of a plant.

• It is made up of one or more Carpels (female reproductive organs). The carpel is present in the center of the flower. 
• Each carpel consists of three parts– stigma, style and ovary.
• Ovary is the swollen and enlarged basal part of the carpel. Each ovary contains one or more ovules which bear the egg cell or the female reproductive cell.
• The egg cell is also called the female germ cell or the female gamete.
• A middle-elongated tube-like part called the style lies on the ovary. Style connects the ovary to the stigma. 
• The terminal part at the tip of the style is the stigma. It receives the pollen grains during pollination and therefore it is sticky.

Structure of Stamen and carpel

Types of Flowers

Flowers can be categorized into two on the basis of presence or absence of the male and female reproductive parts –

Unisexual Flowers- Flowers which have only one reproductive part either stamen or carpel are called unisexual flowers. Example- Papaya and Watermelon

Bisexual flowers- The flowers which have both male and female reproductive parts (stamen and carpel) are called bisexual flowers. Example- Hibiscus and Mustard

Read More: Reproduction in organisms MCQs

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Process of Sexual Reproduction in Plants

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Pollination 

For sexual reproduction in plants, male and female gametes need to fuse. This happens when the pollen grains reach the ovule. Pollination is the act of transferring the pollen grains from the male part (stamen) of the flower to the female part (carpel) of the same or another flower. Pollination is an important step for fertilization to take place. It can be of two types-

• Self Pollination – 

When the transfer of pollen grains takes place from the anther to the stigma of the same flower or another flower on the same plant, it is called self-pollination.

Self Pollination

• Cross Pollination – 

When the transfer of pollen grains from the anther of one flower to the stigma of another flower on another plant takes place, it is called cross-pollination.

Cross Pollination

Pollination can be done with the help of various agents like –

• Wind – In plants, where pollen grains are light, dry and are produced in large numbers, they get carried away by the wind and are deposited on sticky stigmas. Such flowers are inconspicuous and they do not produce nectar. Example – Maize, Wheat, Rice, etc.
• Water – In aquatic plants, pollen grains fall in water and reach the other flower by water currents. Example – Hydrilla, Coconut
• Insects – Brightly colored and nectar producing flowers attract insects like bees and butterflies. The pollen grains stick on the insects wings or feet and are transported to the stigma of another flower. Examples – Orchids, Sunflower, Pea.
• Birds – Hummingbirds, Sun birds, etc
• Reptiles – Garden lizards.
• Mammals – Squirrels, etc

Fertilization

The fusion of male and female gametes inside the ovary of the flower is called fertilization. The product formed after fertilization is called the zygote. Later, the zygote goes under a series of development and division to form the embryo which later grows into a new plant.

Steps of fertilization –

• When the pollen grains land on a suitable stigma, a tube grows out of one end of the pollen grain. It is called the pollen tube.
• The pollen tube travels down the style to reach the ovary where it enters the ovule through an opening called micropyle.
• This process is called the germination of pollen on the stigma.
• The pollen tube contains two male gametes which are deposited in the embryo sac of the ovule.
• In the embryo sac, one male gamete fuses with the female gamete or egg nucleus and forms a zygote.
• The other male gamete fuses with the nucleus of the central cell in the embryo sac to form the endosperm.

Pollen grain germination

Changes in Flower after Fertilization 

1. The fertilized ovum, i.e., the zygote, forms the embryo
2. The ovules change into seeds
3. The ovary grows into a fruit
4. Other parts like sepals and petals fall-off (they might remain intact in some fruits)
5. Seeds are dispersed and they give rise to new plants

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Things to Remember

• Reproduction in plants occur via two modes- asexual and sexual.
• Asexual mode of reproduction includes, vegetative propagation, budding, fragmentation and spore formation.
• Vegetative propagation occurs through vegetative parts of the plant. It can also be done by artificial methods.
• Sexual reproduction involves formation of gametes. In plants, the male gametes are pollen grains whereas the female gametes are eggs or ova.
• Pollination is achieved by the help of various agents like wind, water, insects etc. It can also be done artificially.
• Fusion of male and female gametes is called fertilization.
• After fertilization, zygote forms the embryo, ovule forms the seeds and ovary forms the fruit.