Lecture on Sexual Reproduction in Flowering Plants

Introduction

• Focus: Sexual reproduction in flowering plants (Angiosperms)
• Source: NCERT textbook, crucial for exam preparation
• Key: Understanding NCERT thoroughly, solving previous year questions
• Importance: 3-4 questions in exams
• Connected Chapters: Morphology, Plant Kingdom, Mitosis, Meiosis

Basics of Angiosperms

• Main plant body is sporophyte
• Proton develops hormonal changes leading to reproductive organ development

Flower Structure

Non-essential Parts

• Sepals: Calyx
• Petals: Corolla

Essential Parts

• Stamens: Androecium
  • Structure: Filament, Anther (two lobes, four microsporangia/ pollen sacs)
  • Development: Young to mature anther
  • Tissues: Epidermis, endothecium, middle layer, tapetum
• Function of Tissues: Protection, nutrition, etc.
• Microsporangia: Site for microsporogenesis
  • Microspore mother cells undergo meiosis forming microspores
  • Microspores develop into pollen grains with a vegetative cell and generative cell
• Pistils: Gynoecium
  • Structure: Stigma, Style, Ovary
  • Ovules attached via placenta

Pollination

• Transfer of pollen from anther to stigma
• Types of Pollination: Self and Cross-Pollination
• Agents: Wind, Water, Animals (biotic and abiotic)

Post-Pollination Events

• Pollen tube formation and growth
• Double fertilization: Unique to Angiosperms, discovered by S.G. Nawaschin
• Steps of Double Fertilization
  • One male gamete fuses with egg cell forming zygote (syngamy)
  • Another male gamete fuses with two polar nuclei forming triploid primary endosperm nucleus (triple fusion)
• Result: Formation of zygote and endosperm

Development Post-Fertilization

• Zygote develops into an embryo
• Primary endosperm nucleus develops into endosperm providing nutrition
• Structure of seeds in Monocots and Dicots

Fruits and Seed Dispersal

• Development from ovary
• Pericarp: Fruit wall
• Types: True fruits (developed from ovary) and False fruits (developed from other parts)
• Seed dispersal mechanisms: Wind, water, animals

Parthenocarpy and Apomixis

• Parthenocarpy: Fruit development without fertilization (e.g., Banana)
• Apomixis: Formation of seeds without fertilization, example of asexual reproduction ensuring genetic uniformity

Significance in Agriculture

• Seed viability and production
• Importance of maintaining genetic purity for crop yield and quality

Conclusion

• Understanding concepts from NCERT crucial
• Linkages with related chapters to be understood
• Focus on important questions and previous year papers