Plant Organ Systems and Functions: Forms of Reproduction in Angiosperms

Types of Reproduction

• Asexual Reproduction

  • Offspring emerge from a single parent.
  • Involves no fusion of gametes or fertilization.
  • Offspring are genetically identical to the parent.

• Sexual Reproduction

  • Involves single or self-pollination or cross-pollination.
  • Requires fusion of sperm and egg cells during fertilization.
  • Enhances genetic variation; offspring are not genetically identical to parents.

Asexual Reproduction

• Apomixis
  • Seeds are produced without meiosis or fertilization.
  • Unfertilized eggs in ovules produce embryos.
  • Example: Dandelions reproduce through apomixis, leading to no genetic variation.

Sexual Reproduction

• Vegetative Propagation

  • Plant parts produce buds that develop into new individuals.
  • Example: Strawberries use runners to create new plants from buds.

• Pollination and Fertilization

  • Pollen Grains
    • Contain male gametophytes; each pollen has two sperm nuclei.
    • Tube nucleus helps transport sperm during pollination.
  • Ovules
    • Contain female gametes; embryo sac consists of eight nuclei.
    • Fertilization involves egg nucleus and sperm.

• Double Fertilization

  • Pollen grains land on stigma, pollen tube extends.
  • One sperm nucleus fertilizes the egg nucleus (forms embryo).
  • Other sperm nucleus fertilizes polar nuclei (forms endosperm).
  • Results in diploid embryo and triploid endosperm.

Plant Development

• Tissues and Growth
  • Apical Meristem
    • Allows upward growth of the plant.
  • Cambium
    • Includes cork cambium (woody parts) and vascular cambium (xylem and phloem).
  • Root Apical Meristem
    • Allows downward growth of plant roots.

Embryogenesis

• Seeds mature from ovules, ovary becomes fruit.
• Differentiation into exocarp, mesocarp, and endocarp in fruits.
  • Examples: Apple, peach, grape, orange.

Organogenesis

• Germination Process
  • Seed imbibition ruptures seed coat leading to germination.
  • Radical: Becomes the root.
  • Hypocotyl: Becomes the stem.
  • Cotyledon: Serves as primary embryonic leaves.
  • Epicotyl: Gives rise to mature leaves.

Conclusion

• The lecture covered reproduction in angiosperms, plant development, and organogenesis.
• Encourage questions and provide contact information for further clarification.
• Looking forward to face-to-face discussions.