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Reproduction in Plants

🏫 MP BoardClass 7Science

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Class 7 Science: Chapter - Reproduction in Plants

MP Board (NCERT Curriculum)

### Concept 1: What is Reproduction?

Definition: Reproduction is the process by which living organisms produce new individuals of their own kind. It ensures the continuity of life on Earth.

  • Parent plant: The original plant that gives rise to new plants.
  • Offspring: The new plants produced.

### Concept 2: Modes of Reproduction in Plants

Plants reproduce mainly by two methods:

  1. Asexual Reproduction: New plants are obtained without the production of seeds.
  2. Sexual Reproduction: New plants are obtained from seeds.

### Concept 3: Asexual Reproduction (Types & Methods)

In asexual reproduction, a single parent is involved. Different methods include:

1. Vegetative Propagation

A type of asexual reproduction in which new plants are produced from vegetative parts like roots, stems, leaves, and buds.

  • By Stem: Potato has "eyes" (buds) which grow into new plants (e.g., Ginger, Potato).
  • By Leaves: Bryophyllum (sprout leaf plant) has buds in the margins of leaves that fall off to grow into new plants.
  • By Roots: Sweet potato and Dahlia.
  • Advantages:
    • Plants grow faster.
    • Flowers and fruits are produced earlier.
    • Exact copies of the parent plant are produced.

2. Budding

  • Definition: A small bulb-like projection called a bud arises from the body of the parent organism, grows, detaches, and matures into a new individual.
  • Example: Yeast (a single-celled fungus).

3. Fragmentation

  • Definition: The body of the parent breaks up into two or more pieces (fragments), and each fragment grows into a new individual.
  • Example: Spirogyra (an alga).

4. Spore Formation

  • Definition: Plants produce tiny, lightweight, asexual reproductive bodies called spores that are covered by a hard protective coat to withstand unfavorable conditions. When conditions are favorable, they germinate into new plants.
  • Example: Fungi (like Rhizopus/bread mold), Ferns, and Mosses.

### Concept 4: Sexual Reproduction

In sexual reproduction, male and female gametes (sex cells) fuse to form a zygote, which develops into a seed.

Parts of a Flower (The Reproductive Organ)

  • Stamen (Male reproductive part): Consists of two parts:
    1. Anther: Contains pollen grains (which produce male gametes).
    2. Filament: Supports the anther.
  • Pistil / Carpels (Female reproductive part): Consists of three parts:
    1. Stigma: The sticky top part that receives pollen grains.
    2. Style: The tube-like structure connecting stigma to the ovary.
    3. Ovary: Contains one or more ovules (which contain the female gamete/egg).
  • Unisexual Flowers: Flowers containing either only the stamens or only the pistil (e.g., Corn, papaya, cucumber).
  • Bisexual Flowers: Flowers containing both stamens and pistil (e.g., Mustard, rose, petunia).

### Concept 5: Pollination

  • Definition: The transfer of pollen grains from the anther to the stigma of a flower of the same kind.
  • Types of Pollination:
    1. Self-Pollination: Transfer of pollen from the anther to the stigma of the same flower or another flower of the same plant.
    2. Cross-Pollination: Transfer of pollen from the anther of one flower to the stigma of another flower of the same kind (assisted by agents).
  • Agents of Pollination: Wind, Water, and Insects/Animals (birds, bees).

### Concept 6: Fertilization & Seed Formation

  • Fertilization: The process of fusion of the male gamete (present in pollen grain) with the female gamete (egg in the ovule) to form a zygote.
  • Post-Fertilization Changes:
    • Zygote develops into an embryo.
    • Ovule develops into a seed (contains the baby plant).
    • Ovary ripens and develops into a fruit.
    • Sepals and petals usually wither and fall off.

### Concept 7: Seed Dispersal

  • Definition: The mechanism by which seeds or fruits are scattered away from the parent plant to prevent overcrowding, competition for light, water, and minerals.
  • Agents and Methods of Dispersal:
    1. By Wind: Winged seeds (e.g., Drumstick, Maple), light hairy seeds (e.g., Aak or Madar, Sunflower).
    2. By Water: Seeds or fruits develop floating ability, spongy or fibrous outer coats (e.g., Coconut).
    3. By Animals: Spiny seeds with hooks that get attached to the bodies of animals (e.g., Xanthium, Urena). Also, fruits eaten by animals pass out undamaged in their excreta.
    4. By Explosion: Fruits burst with sudden jerks, scattering seeds far from the parent plant (e.g., Castor, Balsam).