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?
Significance of reproduction
Modes of Reproduction
Types of Asexual reproduction
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 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
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The nucleus (or DNA) of the parent cell duplicates.
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The cell divides into two equal halves.
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Each half gets one copy of the genetic material.
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Two new organisms are formed that are identical to the parent
Examples
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Amoeba – divides into two by simple splitting.
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Paramecium – divides across the center.
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Bacteria – reproduce rapidly through binary fission.
Key Features
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Only one parent is involved.
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No gametes or fertilization.
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New cells are genetically identical to the parent.
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It happens in unicellular organisms, not in higher plants or animals.
Budding
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A small bud appears on the parent’s body.
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The nucleus divides, and one part of it moves into the bud.
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The bud grows in size by receiving nutrients from the parent.
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Finally, the bud separates and becomes a new organism.
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Yeast – A single-celled organism that reproduces by budding.
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Hydra – A small water animal; new Hydra grows as a bud on the parent’s body.
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Only one parent is involved.
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No gametes or fertilization take place.
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The offspring are identical to the parent.
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It occurs in both unicellular and multicellular organisms.
Fragmentation
Example:- Some algae such as spirogyra and oscillatoria
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In spirogyra (a green alga), the long filament breaks into smaller fragments. Each fragment grows into a new spirogyra under suitable conditions.
Key Points:
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It occurs mostly in simple multicellular organisms like algae, fungi, and some worms.
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No gametes (sex cells) are involved.
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Fast and efficient way of reproduction in favorable conditions.
Spore Formation
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Spores are small, light, and have a tough covering that helps them survive in unfavorable conditions like heat or dryness.
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When the environment becomes favorable, the spores germinate and grow into new organisms.
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Fungi like bread mould (Rhizopus) reproduce by forming spores.
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Fern plants also reproduce through spores.
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Spores are protected by a hard wall.
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They help the organism survive harsh conditions.
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It is a fast and common method of reproduction in fungi and lower plants.
Vegetative propagation
Examples:
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Potato grows from its stem tuber.
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Onion grows from its bulb.
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Bryophyllum grows from its leaves.
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Rose and money plant can grow from stem cuttings.
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No seeds or spores are involved.
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The new plant is exactly similar to the parent plant.
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It is a quick and easy way to grow plants.
Natural vegetative propagation
Vegetative propagation by roots
Examples:- Sweet potato, Dahlia, Carrot, Turnip
Examples:
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Bryophyllum – new plants grow from the edges of leaves
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Begonia – new plants grow from leaf cuttings
Examples:
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Strawberry – grows from runners
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Mint – grows from stolons
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Money plant – grows from creeping stems
Key Points:
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No seeds are involved.
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The new plant is identical to the parent plant.
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It is a natural and quick method of reproduction.
Examples:
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Potato – grows from tuber
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Ginger – grows from rhizome
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Onion – grows from bulb
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:
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Potato – grows from the eyes of tubers
Key Points:
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No seeds are involved.
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The new plant is identical to the parent plant.
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It is a natural and quick method of reproduction.
Examples:- Ginger, Turmeric
Key Points:
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No seeds are involved.
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The new plant is identical to the parent plant.
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It helps the plant spread quickly in the soil.
Examples:- Onion, Garlic, Tulip
Key Points:
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No seeds are involved.
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The new plant is identical to the parent plant.
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It is a quick and natural method of reproduction.
Explanation:
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Unlike natural propagation, human intervention is required.
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Methods involve cuttings, grafting, layering, or tissue culture to produce new plants.
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The new plants are genetically identical to the parent plant.
Examples:
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Cutting – Rose, Sugarcane
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Grafting – Apple, Mango
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Layering – Jasmine, Grapevine
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Tissue culture – Banana, Orchids
Key Points:
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Used to grow plants that do not reproduce well by seeds.
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Ensures fast multiplication of plants.
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Produces disease-free and uniform plants
Examples:- Rose, Sugarcane, Grapevine, Bougainvillea
Key Points:
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It is a quick and easy method of producing new plants.
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The new plant is genetically identical to the parent plant.
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Care should be taken to select healthy stems for successful growth.
Explanation:
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A low branch of the parent plant is bent towards the ground.
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The middle part of the branch is covered with moist soil, while the tip remains above the ground.
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After roots develop from the buried part, it is cut and planted as a new plant.
Examples:- Jasmine, Grapevine, Strawberry, Bougainvillea
Key Points:
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It is a simple and natural-looking method of artificial propagation.
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The new plant is identical to the parent plant.
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This method is used for plants that do not grow well from cuttings.
Explanation:
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Two plants of the same kind are used:
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The root part (stock) of one plant.
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The stem part (scion) of another plant.
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The scion is placed over the stock and tied together.
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After some time, they join and grow as one plant, combining the good qualities of both.
Examples:- Mango, Apple, Rose, Orange
Key Points:
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It helps in combining desirable traits (e.g., strong roots + tasty fruits).
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The new plant is genetically identical to the parent scion.
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Commonly used in fruit trees and ornamental plants.
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:
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Selection of plant part (explant) – A small piece of tissue is taken from a healthy plant.
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Sterilization – The explant is cleaned to remove germs.
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Placing in culture medium – It is put in a nutrient-rich medium.
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Incubation – Kept in suitable temperature, light, and humidity.
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Development of plantlet – Cells divide and form a small plant.
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Transplantation – The plantlet is moved to soil.
Advantages of Tissue Culture:
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Produces many plants in a short time.
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Identical (clone) plants are produced.
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Disease-free plants can be grown.
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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,
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The male parent produces male gametes (like pollen in plants or sperm in animals).
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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:
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Formation of gametes – Male and female cells are formed.
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Fertilization – Male and female gametes fuse to form a zygote.
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Development – The zygote grows into a new organism.
Examples:
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In humans, sperm (male) fuses with egg (female).
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In flowering plants, pollen (male) fuses with ovule (female).
Key Features:
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Involves two parents
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Involves fusion of gametes
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Offspring are not identical to parents (they show variation)
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
