Reproduction in Plants

• Introduction

  • Meaning of reproduction (production of new individuals)
  • Importance for species survival
  • Two main types: Asexual and Sexual

• Asexual Reproduction

  • Definition: New plants obtained without production of seeds or spores
  • Vegetative Propagation
    • Definition: New plants from vegetative parts (roots, stems, leaves, buds)
    • Stem cutting (e.g., Rose, Champa)
    • Eyes of Potato (Buds growing into plants)
    • Budding in Ginger/Turmeric (Rhizomes)
    • Leaf buds (e.g., Bryophyllum with buds on leaf margins)
    • Advantages: Quick, exact copies of parent, bear flowers/fruits earlier
  • Budding
    • Process: Small bulb-like projection (bud) develops and detaches
    • Example: Yeast
  • Fragmentation
    • Process: Body breaks into two or more fragments, each growing into a new individual
    • Example: Spirogyra (Algae)
  • Spore Formation
    • Process: Production of lightweight, asexual reproductive bodies (spores) covered by hard protective coats
    • Example: Fungi (e.g., Bread mould), Ferns

• Sexual Reproduction

  • Definition: Fusion of male and female gametes
  • Role of flowers (reproductive parts of a plant)
  • Parts of a Flower
    • Unisexual Flowers: Have either male or female reproductive parts (e.g., Corn, Papaya, Cucumber)
    • Bisexual Flowers: Have both male and female parts (e.g., Mustard, Rose, Petunia)
    • Male Part (Stamen)
      • Anther: Contains pollen grains (male gametes)
      • Filament: Stalk supporting the anther
    • Female Part (Pistil / Carpel)
      • Stigma: Sticky top surface receiving pollen
      • Style: Tube connecting stigma to ovary
      • Ovary: Contains one or more ovules (female gametes / egg cells)
  • Pollination
    • Definition: Transfer of pollen grains from anther to stigma
    • Self-pollination: Transfer within the same flower or same plant
    • Cross-pollination: Transfer from flower of one plant to stigma of another plant of same kind
    • Agents of pollination: Wind, Water, Insects/Animals
  • Fertilization
    • Definition: Fusion of male gamete (pollen grain) and female gamete (egg cell)
    • Forms a zygote
    • Zygote develops into an embryo
  • Fruits and Seed Formation
    • Ovary transforms into a fruit
    • Ovules develop into seeds
    • Other flower parts (sepals, petals) usually wither and fall off

• Seed Dispersal

  • Definition: Scattering of seeds away from the parent plant
  • Importance: Prevents overcrowding, reduces competition for sunlight, water, and minerals, helps invasion of new habitats
  • Agents of Dispersal
    • Wind: Lightweight, winged, or hairy seeds/fruits (e.g., Drumstick, Maple, Sunflower hair/daikon)
    • Water: Spongy or fibrous outer coat helping them float (e.g., Coconut)
    • Animals: Spiny seeds with hooks clinging to fur, or edible fruits passed out intact in droppings (e.g., Xanthium, Urena)
    • Explosion / Bursting: Fruits burst with sudden jerks, scattering seeds far from parent (e.g., Castor, Balsam)