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


Plants reproduce sexually through flowers, which are the reproductive organs.


The process includes gamete formation, pollination, fertilization, and seed formation.




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🌼 Structure of a Flower


A flower has four main whorls:


1. Calyx (sepals) – Protect the bud



2. Corolla (petals) – Attract pollinators



3. Androecium (stamens) – Male reproductive part



4. Gynoecium (carpels) – Female reproductive part





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♂️ Stamen (Male Reproductive Organ)


Made up of:


Anther – Bilobed, pollen-producing


Filament – Stalk holding anther




📍 Microsporangium:


Inside anther, contains pollen sacs


Forms pollen mother cells (PMCs) → undergo meiosis → pollen grains



📍 Microsporogenesis:


Formation of microspores (pollen grains) from PMCs via meiosis


Each microspore develops into a male gametophyte




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♀️ Gynoecium (Female Reproductive Organ)


Made up of:


Stigma – Receives pollen


Style – Tube to ovary


Ovary – Contains ovules




📍 Ovule Structure:


Has integuments, nucellus, embryo sac



📍 Megasporogenesis:


One megaspore mother cell → meiosis → 4 megaspores → only 1 functional



📍 Female Gametophyte (Embryo Sac):


Formed from functional megaspore


7-celled, 8-nucleate structure:


1 egg cell


2 synergids


3 antipodals


1 central cell (with 2 nuclei)





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🍃 Pollination


Transfer of pollen grains from anther to stigma.


Types of Pollination:


1. Autogamy – Same flower



2. Geitonogamy – Different flowers on same plant



3. Xenogamy – Between flowers of different plants




Agents:


Abiotic: Wind, water


Biotic: Insects, birds, animals




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💥 Double Fertilization


Unique to angiosperms


One male gamete fuses with egg → zygote (syngamy)


Other male gamete fuses with central cell → endosperm (triple fusion)



> Syngamy + Triple Fusion = Double Fertilization





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🌱 Post-Fertilization Events


1. Zygote → Embryo



2. Ovule → Seed



3. Ovary → Fruit



4. Endosperm → Nourishment tissue





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🌾 Seed and Fruit Formation


Seed parts: Seed coat, embryo, cotyledons, endosperm (in monocots)


Fruit develops from ovary




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🧠 Important Definitions


Microsporogenesis – Formation of microspores


Megasporogenesis – Formation of megaspores


Syngamy – Fusion of male and female gametes


Double fertilization – Two fusions in one fertilization event


Pollination – Transfer of pollen




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📝 Quick Revision Table


Concept Key Point


Male Gametophyte Pollen grain (2 cells)

Female Gametophyte Embryo sac (7 cells, 8 nuclei)

Pollination Types Autogamy, Geitonogamy, Xenogamy

Double Fertilization Syngamy + Triple fusion

Fruit Developed ovary

Seed Developed ovule




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✅ Summary


Sexual reproduction involves male and female gametophytes


Pollination helps bring male and female gametes together


Double fertilization is uni

que to flowering plants


Fertilization results in zygote and endosperm


Ovule becomes seed, ovary becomes fruit




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✍️ Written by Shahid – Founder of Shahid Notes

📚 Visit: https://shahidnotes12.blogspot.com


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