Sexual Reproduction in Flowering Plants – Class 12 Biology Notes

 🌸 Chapter 2: Sexual Reproduction in Flowering Plants – Class 12 Biology Notes


Label: Biology, Class 12, Reproduction



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🔹 Introduction


Reproduction in angiosperms (flowering plants) occurs through sexual reproduction involving flowers, gametes, and fertilization.




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🌼 Parts of a Typical Flower


Part Description


Sepals (Calyx) Protects flower in bud stage

Petals (Corolla) Bright coloured, attract pollinators

Stamens (Androecium) Male reproductive part (Anther + Filament)

Carpels (Gynoecium) Female reproductive part (Ovary + Style + Stigma)




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🧬 Pre-fertilization Events


1. Development of Male Gametophyte


Microsporogenesis: Formation of microspores (pollen grains) in anther by meiosis


Microspore → Pollen mother cell → Pollen grains


Mature pollen: 2 cells – Generative cell & Vegetative cell



2. Development of Female Gametophyte


Ovule develops inside ovary


Megaspore mother cell → Meiosis → 4 megaspores (1 functional)


Embryo sac (female gametophyte): 7 cells, 8 nuclei


1 Egg cell


2 Synergids


3 Antipodals


1 Central cell (with 2 polar nuclei)





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🌸 Pollination


Transfer of pollen grains from anther to stigma



Types of Pollination:


1. Autogamy – Same flower



2. Geitonogamy – Different flower on same plant



3. Xenogamy – Different plant




Agents of Pollination:


Wind (Anemophily): maize


Water (Hydrophily): Vallisneria


Insects (Entomophily): sunflower


Birds (Ornithophily): hibiscus




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🧪 Outbreeding Devices


Mechanisms to prevent self-pollination:


Dichogamy (anther and stigma mature at different times)


Herkogamy (physical barrier)


Self-incompatibility





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🌱 Double Fertilization (Unique to Angiosperms)


One male gamete fuses with egg → Zygote (Syngamy)


Other fuses with 2 polar nuclei → Endosperm (Triple fusion)


Together called Double Fertilization




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🌿 Post-Fertilization Events


1. Zygote → Embryo



2. Ovary → Fruit



3. Ovule → Seed



4. Endosperm formation (provides nourishment)





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🧠 Seed and Fruit Formation


Structure Develops into


Zygote Embryo

Ovule Seed

Ovary Fruit

Integuments Seed coat




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📌 Important Diagrams to Practice


LS of Flower


Structure of anther


Structure of ovule


Embryo sac (7-celled, 8-nucleated)


Double fertilization process




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🔍 Keywords / Definitions


Microsporogenesis: Formation of microspores


Megasporogenesis: Formation of megaspores


Embryo sac: Female gametophyte


Syngamy: Fusion of male and female gametes


Triple fusion: Fusion of male gamete with two polar nuclei


Endosperm: Nutritive tissue




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✅ Summary


Flower is reproductive organ of angiosperms


Male and female gametes form through meiosis


Pollination brings gametes together


Double fertilization is 

unique to flowering plants


Post-fertilization leads to seed and fruit formation




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✍️ Written by Shahid – Founder of Shahid Notes


📚 Visit Shahid Notes for free Class 12 study material

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