Reproduction in Plants class - 7th CBSE Biology Notes

Reproduction in Plants

Modes of Reproduction in Plants

➥Plants reproduce through two main methods:

1. Asexual Reproduction: Involves a single parent without the formation of seeds.
2. Sexual Reproduction: Involves the fusion of male and female gametes, resulting in seed formation.

1. Asexual Reproduction

➥ Asexual reproduction in plants occurs through various methods:

1. Vegetative Propagation: A new plant grows from parts like roots, stems, or leaves.
1. Through Roots: Plants reproduce using root parts that develop into new plants. Examples: sweet potato, dahlia.
2. Through Stems: Stems act as reproductive parts, storing food and giving rise to new plants. Examples: ginger, potato, onion.
3. Through Leaves: Certain leaves develop buds that grow into new plants. Example: Bryophyllum.
4. Horizontal Stems: Stems grow horizontally on the ground, sprouting new plants at nodes. Examples: grass, strawberry.

2. Artificial Methods of Vegetative Propagation:
1. Cutting: A method where a piece of a plant (such as a stem or leaf) is cut and placed in soil to grow a new plant. Example: Rose.
2. Grafting: A technique where tissues from one plant are joined with those of another to grow a new plant. Example: Mango.
3. Layering: A method in which a stem is bent to the ground, covered with soil, and allowed to develop roots while still attached to the parent plant. Example: Jasmine.
4. Tissue Culture: A modern method of growing plants from small pieces of tissue (cells) in a laboratory setting to create new plants. Example: Various plants in commercial propagation.

3. Other Natural Methods:
1. Budding: A type of asexual reproduction where a new organism develops from a small part of the parent. Example: Yeast.
2. Fragmentation: A process where the body of an organism breaks into pieces, and each piece grows into a new organism. Example: Planaria (flatworms).
3. Spore Formation: A method of reproduction where spores (tiny, reproductive cells) are produced and released to grow into new organisms. Example: Fern and moss.

2. Sexual Reproduction

Sexual Reproduction in Plants

➥ Sexual reproduction in plants involves two parents (male and female) and takes place in the flower, the reproductive organ of the plant. The process includes several steps:

Parts of a Flower

1. Calyx (Sepals): Green and protect the flower before it blooms.
2. Corolla (Petals): Brightly colored, they attract insects or other pollinators.
3. Androecium (Stamens): Male part of the flower that produces pollen grains.
4. Gynoecium (Pistil): Female part that contains the ovary (produces ovules), style (tube), and stigma (where pollen is received).

Steps in Sexual Reproduction

1. Flowering and Gamete Formation

➥Male gametes (pollen) are made in the anthers (part of the stamens). Female gametes (ovules) are made in the ovary (part of the pistil). The stigma collects the pollen.

2. Pollination

➥Pollination is when pollen moves from the anther to the stigma.

1. Self-pollination: Pollen from the same flower fertilizes the ovule.
2. Cross-pollination: Pollen from one flower fertilizes the ovule of another.
3. Pollination can happen through wind, insects, birds, or water.

3. Fertilization

➥ After pollination, a pollen tube grows down the style to the ovary. The male gametes travel through the pollen tube to the ovule. The male gamete fuses with the female gamete (egg cell) to form a zygote. The zygote develops into an embryo inside the seed.

4. Seed and Fruit Formation

➥ The ovule turns into a seed. The ovary becomes a fruit that contains the seed. The fruit protects the seed and helps it spread.

Seed Dispersal

➥ Seed dispersal helps plants spread to new areas. Methods include:

1. By Wind: Seeds of dandelion and maple.
2. By Water: Seeds of coconut.
3. By Animals: Seeds of guava and mango.
4. By Explosion: Fruits like pea and balsam.

5. Seed Germination

➥ When conditions are right, the seed germinates. The embryo inside the seed grows into a new plant.

1. Moisture: Water activates enzymes and softens the seed coat.
2. Temperature: Seeds need an optimum temperature for growth.
3. Oxygen: For respiration during growth.
4. Light: Some seeds require light for germination.

Examples of Plants That Reproduce Sexually

1. Pea plants (Pisum sativum)
2. Sunflower (Helianthus annuus)
3. Apple trees (Malus domestica)

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