Lecture: Reproduction of Flowering Plants

Overview

• Focus on the reproduction of flowering plants.
• Introduction to new terminology related to plant life cycles.
• Discussion of multicellular gametophyte and sporophyte phases.

Key Life Cycle Phases

• Gametophyte:
  • Always haploid and multicellular.
  • Produces gametes through mitosis.
• Sporophyte:
  • Always diploid and multicellular.
  • Produces spores through meiosis.
  • Alternation between haploid phase and diploid phase.

Mosses as a Model

• Mosses are among the first land plants.
• Gametophyte Stage:
  • Mosses spend most of their life in this stage, known as gametophyte dominant.
  • Photosynthesis occurs in the multicellular gametophyte.

Moss Reproductive Structures

• Archegonium:
  • Produces and contains the egg (ovule).
  • Embryo develops within.
• Antheridium:
  • Produces and releases sperm.
  • Sperm are flagellated and require water for movement to the egg.

Fertilization and Sporophyte Development

• Fertilization results in a diploid cell.
• Embryo develops into the sporophyte on the gametophyte.
• Sporangium:
  • Structure where spores are produced by meiosis.

Life Cycle in Different Plants

• Differences in gametophyte and sporophyte stages across plant types.
• Gymnosperms and Angiosperms:
  • Increase in sporophyte dominance.
  • Reduction in gametophyte size.
  • Pollen as male gametophyte; wind-dispersal utilized.

Terminology in Plant Reproduction

• Male and Female Designations:
  • Based on gamete size: large gamete is female, small is male.
• Prefixes:
  • "Mega" for female structures (e.g., megaspore).
  • "Micro" for male structures (e.g., microspore).

Angiosperm Reproduction

• Megaspore and Microspore Pathways:
  • Megaspore mother cell: diploid, produces megaspore → female gametophyte.
  • Microspore mother cell: diploid, produces microspore → male gametophyte.
• Structures in Angiosperms:
  • Female gametophyte: embryo sac.
  • Male gametophyte: pollen.

Conclusion

• Understanding the transition from spore to gametophyte and gametes production is key to studying plant reproduction.
• Next focus will be on flowering plants (angiosperms).