Reproduction In Plants Class 7 Free Notes and Mind Map (Free PDF Download)

Plants have two primary methods of reproduction: asexual and sexual.

Asexual Reproduction

Asexual reproduction allows plants to create offspring without seeds. One common form is vegetative propagation, where new plants emerge from parts like roots, stems, leaves, or buds. This process relies on the plant’s vegetative structures. Examples include:

Burying a cutting from a rose or champa in soil to sprout a new plant.
Growing a money plant in a water container.
Cultivating ginger or turmeric from their underground parts.
Bryophyllum, known as the sprout leaf plant, develops buds along its leaf edges. When a leaf drops onto damp soil, each bud can grow into a new plant.
Potatoes sprout new plants from their “eyes” (buds).
Sweet potatoes and dahlias propagate from their roots.
Cacti can regenerate new plants from separated sections.

Budding

Budding is an asexual reproduction technique. A yeast cell produces a small, bulb-shaped outgrowth called a bud. This bud enlarges, separates from the parent cell, and becomes an independent yeast cell. The new cell matures and may generate additional yeast cells. Occasionally, a second bud forms from the first, leading to a sequence of buds. This rapid process enables yeast to multiply quickly with adequate nutrients. Yeast, a microscopic single-celled organism, thrives and reproduces swiftly under favorable conditions.

Fragmentation

Fragmentation is another asexual reproduction method where an organism splits into multiple pieces, each growing into a new individual.

Organisms: Algae use fragmentation to reproduce.
Process: An alga divides into two or more segments, and each segment develops into a standalone organism.
Conditions: This process accelerates when water and nutrients abound, allowing algae to spread widely in a short time.
Example: Spirogyra, a type of alga, reproduces via fragmentation.

Spore Formation

Spore formation is an asexual reproductive strategy.

Spores: Spores are reproductive units protected by a tough outer layer, enabling them to endure harsh conditions like extreme heat or dryness. When conditions improve, spores germinate and grow into new organisms.
Organisms: Fungi, mosses, and ferns rely on spore formation. For instance, mold on bread develops from airborne spores.
Process: Spores are released into the air, their lightweight nature allowing them to travel great distances.

Sexual Reproduction

Sexual reproduction in plants involves producing new individuals from seeds. Flowers serve as the reproductive organs, with stamens functioning as the male part and pistils as the female part.

Flowers: Unisexual flowers have either pistils or stamens, while bisexual flowers contain both. Examples of unisexual flowers include corn, papaya, and cucumber; bisexual flowers include mustard, rose, and petunia.
Pollination: This is the process of moving pollen, which carries male gametes, from the anther to the stigma of a flower.
Self-pollination: Pollen transfers to the stigma of the same flower or another flower on the same plant.
Cross-pollination: Pollen reaches the stigma of a flower on a different plant of the same species.
Pollen grains are lightweight with a durable coating to resist drying and can be transported by wind, water, or insects.
Fertilization: The female gamete (egg) forms in the ovule. Fertilization occurs when male and female gametes fuse to create a zygote, which develops into an embryo.
Fruit and Seed Development: Post-fertilization, the ovary transforms into a fruit, and ovules become seeds. Seeds house an embryo within a protective coat. Fruits can be soft and juicy, like mangoes and oranges, or hard, like almonds and walnuts.

Pollination

Pollination involves transferring pollen from a flower’s anther to its stigma.

Process: Pollen moves from the anther to the stigma of the same or a different flower.
Types:
Self-pollination: Pollen lands on the stigma of the same flower or another flower on the same plant.
Cross-pollination: Pollen reaches the stigma of a flower on a separate plant of the same species.
Pollen Grains: These have a sturdy outer layer to prevent desiccation and contain male gametes.
Pollination Agents: Wind, water, and insects facilitate pollen transfer. Insects are drawn to flowers’ vibrant colors and scents, carrying pollen on their bodies. Lightweight pollen can also travel via wind or water.

Fruit and Seed Development

Following fertilization, the ovary matures into a fruit, while other flower parts wither. The fruit is the ripened ovary, and seeds form from the ovules. Each seed encases an embryo in a protective layer. Fruits vary from succulent types, such as mangoes and oranges, to tough ones, like almonds and walnuts.

Seed Dispersal

Seed dispersal refers to the mechanism by which seeds and fruits are transported to new locations, promoting plant growth across diverse areas.

Purpose of Dispersal:
Prevents overcrowding and competition for resources like sunlight, water, and nutrients if all seeds germinated in one spot.
Reduces rivalry between a parent plant and its seedlings.
Allows plants to colonize new territories for broader distribution.
Dispersal Methods:
Wind: Lightweight or winged seeds, such as those of drumsticks and maples, or hairy seeds like aak (Madar) and sunflower fruits, are carried by breezes to distant locations.
Water: Some seeds or fruits, like coconuts, develop buoyant features such as spongy or fibrous coatings to float on water.
Animals: Seeds with hooks or spines, such as Xanthium and Urena, latch onto animals and are transported elsewhere.
Bursting: Certain fruits, like castor and balsam, explode suddenly, flinging seeds away from the parent plant.
Dispersal benefits plants by reducing congestion, minimizing resource competition, and enabling expansion into new habitats.