Reproduction in Plants - Class 7 Science - Question and Answer

Reproduction is one of the most important characteristics of living organisms. It is the process by which living things produce new individuals of their own kind. In plants, reproduction ensures the continuation of the species and the spread of plant life on Earth. Plants reproduce in different ways – some through seeds, while others through parts like stems, roots, or leaves.

This chapter, “Reproduction in Plants,” introduces students to the fascinating world of how plants give rise to new plants. It explains the two main types of reproduction – asexual and sexual reproduction. You will learn about various asexual methods such as budding, fragmentation, spore formation, and vegetative propagation, as well as the structure and function of flowers in sexual reproduction.

Reproduction in Plants - Class 7 Science - Question and Answer

What is Reproduction?

Ans:- The process of producing young ones of their own kind is called reproduction. It is the process by which existing living organisms produce new young ones of their own kind.

Ex:- A cat produce kitten which grow into adult cat.

A seed grow into young seedlings and after some time young seedlings becomes big tree.

Significance of reproduction

Some significance of reproduction are

1- It is necessary for the perpetuation of a species

2- It helps in maintaining the composition of population pf infants, youngs, adults and the aged.

3- It replaced the individuals killed due to disease, predation, etc.

4- It introduces new variations in organisms. It also transfers variations from one generation to the next.

Modes of Reproduction

Plants can be reproduction by two methods.

1- Asexual reproduction

2- Sexual reproduction

Asexual Reproduction in plant

Asexual reproduction in plants is the process by which new plants are produced from a single parent plant without the involvement of seeds, flowers, or fusion of male and female gametes. It is a method of reproduction in which a new plant grows from the vegetative parts (like roots, stems, or leaves) of the parent plant without the formation of seeds. The new individual is identical to the parent.

Types of Asexual reproduction

There are five types of Asexual reproduction

1- Binary fission

2- Budding

3- Fragmentation

4- Spore formation

Binary fission

Binary fission is a type of asexual reproduction in which a single parent cell divides into two equal parts, and each part grows into a new organism.

It is a simple and quick method of reproduction seen mostly in unicellular (single-celled) organisms. It is the process by which one parent cell splits into two identical daughter cells, each having a copy of the parent’s genetic material.

Steps of Binary Fission

The nucleus (or DNA) of the parent cell duplicates.
The cell divides into two equal halves.
Each half gets one copy of the genetic material.
Two new organisms are formed that are identical to the parentExamples
- Amoeba – divides into two by simple splitting.
- Paramecium – divides across the center.
- Bacteria – reproduce rapidly through binary fission.

Examples

Amoeba – divides into two by simple splitting.
Paramecium – divides across the center.
Bacteria – reproduce rapidly through binary fission.

Key Features

Only one parent is involved.
No gametes or fertilization.
New cells are genetically identical to the parent.
It happens in unicellular organisms, not in higher plants or animals.

Budding

Budding is a type of asexual reproduction in which a small outgrowth or bud develops on the parent organism. This bud grows, and when it becomes mature, it detaches from the parent to form a new independent organism. It is the process of asexual reproduction in which a new organism develops from a small bud growing on the body of the parent organism.

Steps of Budding

A small bud appears on the parent’s body.
The nucleus divides, and one part of it moves into the bud.
The bud grows in size by receiving nutrients from the parent.
Finally, the bud separates and becomes a new organism.

Examples

Yeast – A single-celled organism that reproduces by budding.
Hydra – A small water animal; new Hydra grows as a bud on the parent’s body.

Key Features

Only one parent is involved.
No gametes or fertilization take place.
The offspring are identical to the parent.
It occurs in both unicellular and multicellular organisms.

Fragmentation

Fragmentation is a type of asexual reproduction in which an organism breaks into two or more pieces, and each piece grows into a new, complete organism.

Example:- Some algae such as spirogyra and oscillatoria

In spirogyra (a green alga), the long filament breaks into smaller fragments. Each fragment grows into a new spirogyra under suitable conditions.

Key Points:

It occurs mostly in simple multicellular organisms like algae, fungi, and some worms.
No gametes (sex cells) are involved.
Fast and efficient way of reproduction in favorable conditions.

Spore Formation

Spore formation is a type of asexual reproduction in which an organism produces tiny spores that can grow into new individuals.

Explanation:

Spores are small, light, and have a tough covering that helps them survive in unfavorable conditions like heat or dryness.
When the environment becomes favorable, the spores germinate and grow into new organisms.

Examples:

Fungi like bread mould (Rhizopus) reproduce by forming spores.
Fern plants also reproduce through spores.

Key Points:

Spores are protected by a hard wall.
They help the organism survive harsh conditions.
It is a fast and common method of reproduction in fungi and lower plants.

Vegetative propagation

Vegetative propagation is a type of asexual reproduction in plants where a new plant grows from the vegetative parts of an old plant such as the root, stem, or leaf instead of seeds.

Examples:

Potato grows from its stem tuber.
Onion grows from its bulb.
Bryophyllum grows from its leaves.
Rose and money plant can grow from stem cuttings.

Key Points:

No seeds or spores are involved.
The new plant is exactly similar to the parent plant.
It is a quick and easy way to grow plants.

Types of vegetative Propagation

1- Natural vegetative propagation

2- artificial vegetative propagation

Natural vegetative propagation

Natural vegetative propagation is a type of asexual reproduction in which new plants grow naturally from the vegetative parts (root, stem, or leaf) of the parent plant without human help.

Types of Natural vegetative propagation

1- Vegetative propagation by roots

2- Vegetative propagation by leaves

3- Vegetative propagation by sub-aerial stems

4- Vegetative propagation by stem

Vegetative propagation by roots

Vegetative propagation by roots is a type of natural vegetative propagation in which new plants grow from the roots of the parent plant.

Examples:- Sweet potato, Dahlia, Carrot, Turnip

Vegetative propagation by leaves

Vegetative propagation by leaves is a type of natural vegetative propagation in which new plants grow from the leaves of the parent plant. Some plants have leaves that can produce buds or small plantlets. These plantlets grow into new independent plants when they fall on the soil.

Examples:

Bryophyllum – new plants grow from the edges of leaves
Begonia – new plants grow from leaf cuttings

Vegetative propagation by sub-aerial stems

Vegetative propagation by sub-aerial stems is a type of natural vegetative propagation in which new plants grow from stems that grow above the ground but lie on or just above the soil. Some plants produce creeping or trailing stems that touch the ground at certain points. At these points, the stem can develop roots and grow into a new plant.

Examples:

Strawberry – grows from runners
Mint – grows from stolons
Money plant – grows from creeping stems

Key Points:

No seeds are involved.
The new plant is identical to the parent plant.
It is a natural and quick method of reproduction.

Vegetative propagation by stem

Vegetative propagation by stem is a type of natural vegetative propagation in which new plants grow from the stem of the parent plant. The stem of some plants has special structures like tubers, rhizomes, runners, or bulbs that can grow into new plants.

Examples:

Potato – grows from tuber
Ginger – grows from rhizome
Onion – grows from bulb

Types of vegetative propagation by stem

1-by tuber

2- by rhizome

3- by bulb

vegetative propagation by stem (by tuber)

Vegetative propagation by stem (by tuber) is a type of natural vegetative propagation in which new plants grow from underground swollen stems called tubers. Tubers are thickened, fleshy stems that store food. Each tuber has buds (called eyes) that can grow into new plants.

Example:

Potato – grows from the eyes of tubers

Key Points:

No seeds are involved.
The new plant is identical to the parent plant.
It is a natural and quick method of reproduction.

Vegetative propagation by rhizome

Vegetative propagation by stem (by rhizome) is a type of natural vegetative propagation in which new plants grow from underground horizontal stems called rhizomes. Rhizomes are thick, horizontal underground stems that store food. They have nodes and buds, and new shoots grow from these buds to form new plants.

Examples:- Ginger, Turmeric

Key Points:

No seeds are involved.

The new plant is identical to the parent plant.

It helps the plant spread quickly in the soil.

Vegetative propagation by bulb

Vegetative propagation by stem (by bulb) is a type of natural vegetative propagation in which new plants grow from underground swollen stems called bulbs. Bulbs are short, vertical, underground stems surrounded by fleshy leaves that store food. The buds on the bulb grow into new plants.

Examples:- Onion, Garlic, Tulip

Key Points:

No seeds are involved.
The new plant is identical to the parent plant.
It is a quick and natural method of reproduction.

Artificial vegetative propagation

Artificial vegetative propagation is a type of asexual reproduction in plants in which humans help to grow new plants from the vegetative parts (stem, root, or leaf) of a parent plant.

Explanation:

Unlike natural propagation, human intervention is required.
Methods involve cuttings, grafting, layering, or tissue culture to produce new plants.
The new plants are genetically identical to the parent plant.

Examples:

Cutting – Rose, Sugarcane
Grafting – Apple, Mango
Layering – Jasmine, Grapevine
Tissue culture – Banana, Orchids

Key Points:

Used to grow plants that do not reproduce well by seeds.
Ensures fast multiplication of plants.
Produces disease-free and uniform plants

Artificial vegetative propagation by stem cutting

Artificial vegetative propagation by stem cutting is a method in which new plants are grown by cutting a piece of stem that has a node from the parent plant.

Examples:- Rose, Sugarcane, Grapevine, Bougainvillea

Key Points:

It is a quick and easy method of producing new plants.

The new plant is genetically identical to the parent plant.

Care should be taken to select healthy stems for successful growth.
Artificial vegetative propagation by layering

Artificial vegetative propagation by layering is a method in which a branch of a plant is bent down and covered with soil. Before covering the branch in soil make a cut on it, so that roots develop from the covered part. Once roots grow, the new plant is separated from the parent plant.

Explanation:

A low branch of the parent plant is bent towards the ground.
The middle part of the branch is covered with moist soil, while the tip remains above the ground.
After roots develop from the buried part, it is cut and planted as a new plant.

Examples:- Jasmine, Grapevine, Strawberry, Bougainvillea

Key Points:

It is a simple and natural-looking method of artificial propagation.
The new plant is identical to the parent plant.
This method is used for plants that do not grow well from cuttings.

Artificial vegetative propagation by grafting

Grafting- Grafting is a very common method of artificial vegetation propagation in fruit plants like mango. New varieties can be developed by this method, the root portion is taken from one plant. This is called the stock. The stem portion , with several buds , is taken from another plants called the scion. The ends of the stock and the scion are obliquely cut and firmly tied together. In this manner, a new plant variety is developed.

Explanation:

Two plants of the same kind are used:
- The root part (stock) of one plant.
- The stem part (scion) of another plant.
The scion is placed over the stock and tied together.
After some time, they join and grow as one plant, combining the good qualities of both.

Examples:- Mango, Apple, Rose, Orange

Key Points:

It helps in combining desirable traits (e.g., strong roots + tasty fruits).
The new plant is genetically identical to the parent scion.
Commonly used in fruit trees and ornamental plants.

Tissue culture or Micropropagation

Tissue culture is a laboratory technique in which cells of plants or animals are grown in an artificial, controlled environment separate from the parent organism. This method is widely used in research and agriculture to propagate plants, study cell biology, and produce disease-free organisms. The other name of tissue culture is micropropagation.

Explanation

In this method, a small part of a plant — such as a leaf, stem, or root — is taken and placed in a nutrient-rich gel or liquid (called culture medium).
This medium contains minerals, vitamins, hormones, and sugar that help the cells grow and form a new plant.

Steps in Tissue Culture:

Selection of plant part (explant) – A small piece of tissue is taken from a healthy plant.
Sterilization – The explant is cleaned to remove germs.
Placing in culture medium – It is put in a nutrient-rich medium.
Incubation – Kept in suitable temperature, light, and humidity.
Development of plantlet – Cells divide and form a small plant.
Transplantation – The plantlet is moved to soil.

Advantages of Tissue Culture:

Produces many plants in a short time.
Identical (clone) plants are produced.
Disease-free plants can be grown.
Plants can be grown throughout the year.

Examples:

Tissue culture is used in growing banana, orchid, sugarcane, and potato plants.

Sexual Reproduction

Sexual reproduction is a type of reproduction that involves the fusion of male and female gametes (sex cells) to form a zygote, which grows into a new organism.

Explanation

In sexual reproduction,

The male parent produces male gametes (like pollen in plants or sperm in animals).
The female parent produces female gametes (like ovules in plants or eggs in animals).

When these two gametes combine (fuse), they form a zygote.
This zygote grows and develops into a new individual that inherits features from both parents.

Steps of Sexual Reproduction:

Formation of gametes – Male and female cells are formed.
Fertilization – Male and female gametes fuse to form a zygote.
Development – The zygote grows into a new organism.

Examples:

In humans, sperm (male) fuses with egg (female).
In flowering plants, pollen (male) fuses with ovule (female).

Key Features:

Involves two parents
Involves fusion of gametes
Offspring are not identical to parents (they show variation)

Sexual Reproduction in Flowering Plants

Sexual reproduction in flowering plants is the process by which male and female gametes (sex cells) fuse to form a zygote, which later develops into a seed. This process ensures variation and the continuation of plant species.

Main Stages of Sexual Reproduction in Flowering Plants

1. Structure of a Flower

A flower is the reproductive part of a plant. It has four main parts:

1- Sepals (Calyx): Green leaf-like structures that protect the flower in its bud stage.

2- Petals (Corolla): Brightly colored parts that attract insects for pollination.

3- Stamens (Androecium): The male reproductive organ, consisting of anther and filament

Anther – produces pollen grains (male gametes)

Filament – a stalk that supports the anther.

4- Carpel/Pistil (Gynoecium): The female reproductive organ, consisting of:

Stigma – receives pollen.

Style – a tube connecting stigma and ovary.

Ovary – contains one or more ovules (female gametes).

Flowers which have both the pistil and stamens are called bisexual flowers.

Ex:- pea, rose, china rose, mustard etc

Flowers which have either pistil or stamens are called unisexual flowers.

Ex:- papaya, cucumber, mulberry, corn etc

Reproduction in Plants - Class 7 Science - Question and Answer

Reproduction in Plants - Class 7 Science - Question and Answer