DAV Class 7 Science Chapter 9 Notes – Reproduction in Plants

These DAV Class 7 Science Notes and DAV Class 7 Science Chapter 9 Notes – Reproduction in Plants act as excellent revision resources, particularly in preparation for board exams.

Reproduction in Plants Class 7 DAV Notes

→ Reproduction: The process by which organisms can produce more of their own kind is called reproduction.

→ Types of Reproduction: There are two main types of reproduction, viz. asexual reproduction and sexual reproduction.

→ Asexual Reproduction: In this mode of reproduction, an individual can reproduce on its own. It does not need involvement of another individual of the same species. Following are the various methods of asexual reproduction:

→ Budding: In this method, an outgrowth is produced by the organism. This outgrowth is called bud. The bud grows to a certain size and gets detached from the mother organism. The bud is then ready to lead an independent life. Examples: Yeast, hydra, etc.

→ Fragmentation: In this method, the organism breaks into many fragments. Each fragment then develops into a new individual. Example: Spirogyra.

→ Spore Formation: In this method, a spore bearing organ develops on the organism. This is called sporangium. The sporangium produces minute round bodies, called spores. Spores come out of the sporangium and are spread far and wide through air and water. When a spore gets a suitable condition, it germinates to produce a new individual. Examples: Rhizopus (bread mould), some bacteria, some fungi.

DAV Class 7 Science Chapter 9 Notes - Reproduction in Plants

→ Vegetative Propagation: This method is used by higher plants. A new plant is produced from vegetative part of the plant. Roots, stem and leaves are the vegetative parts.
1. Vegetative Propagation from stem: In some plants, vegetative propagation happens from stem. For example; potato is a modified stem. Farmers cut the potato in many pieces and bury them under the soil. You can see many notches on the surface of potato. These are called ‘eyes’ of potato. A new plant emerges from an ‘eye’ of the potato. Similarly, stems of many plants; like sugarcane, rose, croton, etc. arc capable of vegetative propagation.

2. Vegetative Propagation from leaves: Leaves of Bryophyllum are capable of vegetative propagation. New plantlets develop from the notches on the leaf margin. These plantlets grow into a new plant.

3. Vegetative Propagation from roots: Roots of some plants are capable of vegetative propagation. Example; sweet potato, dahlia, etc.

→ Advantages of Vegetative Propagation:

  • Plant takes less time to grow and bear flowers and fruits, compared to plants which grow from seeds.
  • The new plant is exact copy of its parent.

→ Disadvantages of Vegetative Propagation:

  • Diseases may spread from parent plant to offspring.
  • Variations are not possible through vegetative asexual reproduction.

→ Sexual Reproduction: In Sexual reproduction, two individuals are involved in the process of reproduction. In flowering plants, the reproductive parts are located on flower.

→ Parts of flower: A typical flower has following main parts:

  1. Sepals: Sepals are green in colour and are leaf-like structures. They protect the inner parts of the flower at budding stage.
  2. Petals: Petals are usually of bright colours; like red, yellow, orange, pink, etc. The bright colour of petals attracts insects. This helps in pollination.
  3. Stamen: Stamen is the male reproductive part of a flower. It is composed of an anther and a filament. The anther produces pollen grains.
  4. Ovary: Ovary is the female reproductive part of a flower. It lies in the centre of a flower. It has a swollen base and a long tube-like structure on top. The top part is called stigma and the swollen base is called ovary. Ovary produces ovules.

DAV Class 7 Science Chapter 9 Notes - Reproduction in Plants

→ Unisexual and Bisexual Flower: If both male and female parts are present, the flower is called bisexual. If either of them is present, the flower is called unisexual.

→ Pollination: The transfer of pollen grains from anthers to the stigma is called pollination. Pollination can be of two types, viz. self pollination and cross pollination.

→ Self Pollination: When pollen grains are transferred to the stigma of the same flower, it is called self pollination.

→ Cross Pollination: When pollen grains are transferred to the stigma of a different flower, it is called cross pollination. Cross pollination can happen on the same plant or between different plants. For cross pollination, plants need help of various agents of pollination. Insects are the major agents of cross pollination. When an insect sits on a flower, pollen grains stick to its legs. When the same insect sits on a different flower, pollen grains are deposited on the stigma. Wind, animals and water are other agents of pollination.

→ Fertilization: Fusion of male and female gametes is called fertilization. Gamete is a specialized cell which is involved in reproduction. Pollen grain germinates on stigma and produces a pollen tube. The pollen tube pierces through the walls of the style and reaches the ovary. Pollen nucleus is transferred to the ovary via pollen tube. Fertilization occurs in the ovary. The product of fertilization is called zygote. Zygote finally develops into a seed. Seed can be defined as a baby plant which is enclosed in seed coat.
After fertilization, petals and sepals usually fall off. Ovary develops into a fruit, so that nutrition can be provided to the developing seed.

→ Germination of Seed: When a seed gets proper moisture, temperature and oxygen; it germinates to produce a new plant.

→ Dispersal of Seeds: If all the seeds would fall near the parent plant and germinate, there would be too many plantlets in a smaller area. The plant lets shall not be able to get adequate amount of sunlight, oxygen, moisture, etc. As a result, most of the plants would not survive. Hence, it is important that new plants grow up far away from the parent plant. For this, the seeds should be spread far and wide. This is called dispersal of seeds. Plants need the help of various agents for seed dispersal. Some of them are given here.

→ Dispersal by Wind: Seeds of some plants are lightweight and may have some structure which helps them float on air. For example; the seeds of dandelion have hair-like structures. Due to them, the seed of dandelion floats on air. Seeds of drumstick and maple have wing-like structures. Seed of madar (aak) has hair-like structures.

→ Dispersal by Water: Seeds and fruits of some plants can float on water. Thus, seeds of such plants get dispersed. Examples; water lily and coconut.

→ Dispersal by Animals: Some animals eat many fruits and spread the seeds in the process. Some of the seeds also get spread through animal droppings. Seeds of some plants have spine-like structures; which help them in sticking the fur of animals and thus the seeds get dispersed. Examples: urena, lotus fruits, etc.

→ Dispersal by Explosion: Some fruits burst open when they mature. The force of bursting is enough to spread the seeds.
Words that Matter

→ Reproduction: The process by which an organism produces its offspring.

DAV Class 7 Science Chapter 9 Notes - Reproduction in Plants

→ Asexual Reproduction: When a single parent is involved in reproduction, it is called asexual reproduction.

→ Sexual Reproduction: When two parents are involved in reproduction, it is called sexual reproduction.

→ Vegetative Propagation: When vegetative parts of a flowering plant produce a new plant, it is called vegetative propagation.

→ Fertilization: The process of fusion of male and female gamete.

→ Zygote: The product of fertilization.

→ Pollination: Transfer of pollen grains from anther to stigma.

→ Seed Dispersal: The process of spreading the seeds far and wide.