Bihar Board - Class 12 Biology - Chapter 2: Sexual Reproduction in Flowering Plants Handwritten Notes

Sexual reproduction in flowering plants involves the formation and fusion of male and female gametes, resulting in the production of seeds and fruits. This process ensures genetic variation and adaptation in plants. Flowering plants, or angiosperms, are the most advanced group of plants, with flowers serving as their reproductive structures.

Key Points

1. Structure of a Flower

   • Essential Whorls:
     • Androecium: Male reproductive part consisting of stamens (filament and anther).
     • Gynoecium: Female reproductive part comprising the pistil (stigma, style, and ovary).
   • Accessory Whorls: Sepals (calyx) and petals (corolla), which aid in protection and attraction of pollinators.

2. Pre-Fertilization Events

   • Pollination: Transfer of pollen grains from anther to stigma, which can be:
     • Self-Pollination (Autogamy): Pollen transferred within the same flower.
     • Cross-Pollination (Xenogamy): Pollen transferred to a different flower.
   • Agents of Pollination: Includes wind, water, insects, birds, and animals.
   • Pollen-Pistil Interaction: Recognition and acceptance/rejection of pollen by the stigma.

3. Fertilization

   • Double Fertilization: Unique to angiosperms, involving:
     • One male gamete fuses with the egg cell to form a zygote (syngamy).
     • Another male gamete fuses with the central cell to form the triploid primary endosperm nucleus (PEN).
   • Results in the formation of seed and fruit.

4. Post-Fertilization Events

   • Seed Development: Ovule develops into a seed, containing the embryo and endosperm.
   • Fruit Formation: Ovary matures into a fruit, protecting the seeds and aiding in dispersal.

5. Significance of Sexual Reproduction

   • Introduces genetic variation, essential for evolution.
   • Facilitates the formation of new species.
   • Ensures the production of seeds and fruits for plant propagation and survival.

Conclusion

Sexual reproduction in flowering plants is a complex and efficient process that ensures the survival, genetic diversity, and adaptability of plants. Understanding this process is essential for advancements in agriculture, horticulture, and plant breeding.