Sexual Reproduction in Flowering Plants

• Introduction

  • Definition of Sexual Reproduction
  • Flower as the reproductive organ

• Pre-fertilization: Structures and Events

  • Stamen, Microsporangium, and Pollen Grain
    • Structure of Microsporangium (Wall layers: Epidermis, Endothecium, Middle layers, Tapetum)
    • Microsporogenesis and pollen mother cells (PMC)
    • Structure of Pollen Grain (Exine, Intine, Germ pores)
    • Economic importance and viability of pollen
  • Pistil, Megasporangium (Ovule), and Embryo Sac
    • Structure of pistil (Carpel, Stigma, Style, Ovary)
    • Anatomy of Megasporangium / Ovule (Micropyle, Funicle, Nucellus, Integuments)
    • Megasporogenesis and functional megaspore
    • Structure of Embryo Sac (Female gametophyte: 7-celled, 8-nucleate condition, Egg apparatus, Antipodals, Central cell)
  • Pollination
    • Definition and types
    • Autogamy (Self-pollination within the same flower)
    • Geitonogamy (Pollination between flowers of the same plant)
    • Xenogamy (Cross-pollination between different plants)
    • Agents of Pollination
      • Abiotic agents (Wind - Anemophily, Water - Hydrophily)
      • Biotic agents (Insects, birds, bats - Zoophily)
    • Outbreeding devices (Mechanisms to prevent self-pollination)

• Pollen-Pistil Interaction

  • Recognition of compatible pollen
  • Pollen tube growth through style
  • Artificial hybridisation techniques (Emasculation and Bagging)

• Double Fertilization

  • Syngamy (Male gamete + Egg cell $\rightarrow$ Zygote $\rightarrow$ Embryo)
  • Triple Fusion (Male gamete + Two polar nuclei $\rightarrow$ Primary Endosperm Nucleus / PEN)
  • Formation of Primary Endosperm Cell (PEC)

• Post-fertilization: Events and Structures

  • Endosperm Development
    • Types (Nuclear, Cellular, Helobial)
    • Function (Nutrient supply to embryo)
  • Embryogenesis
    • Development of dicot embryo (Proembryo, Globular, Heart-shaped, Mature embryo)
    • Development of monocot embryo (Scutellum, Coleoptile, Coleorhiza)
  • Seed Formation
    • Transformation of ovule into Seed
    • Types of seeds (Albuminous/Non-albuminous, Alkaline/Non-endospermic)
    • Dormancy and desiccation
  • Fruit Formation
    • Transformation of ovary into Fruit
    • Types of fruits (True fruits, False fruits - e.g., Apple, Strawberry)
    • Parthenocarpy (Seedless fruits without fertilization - e.g., Banana)

• Special Modes of Reproduction

  • Apomixis (Seed formation without fertilization - e.g., Asteraceae, Grasses)
  • Polyembryony (Occurrence of more than one embryo in a seed - e.g., Citrus, Mango)