Sexual reproduction in flowering plants Class 12 Notes is one of the most important chapters of Class 12 Biology. This chapter explains how flowering plants reproduce sexually through the formation of male and female gametes, pollination, fertilization, seed development, and fruit formation. Questions from this chapter are frequently asked in board examinations, NEET, and other competitive exams.

The topic is concept-based and includes many biological processes such as microsporogenesis, megasporogenesis, pollination, double fertilization, embryo development, and seed formation. Understanding this chapter thoroughly helps students score high marks because most questions are directly framed from NCERT lines.

In this blog, you will find Sexual Reproduction in Flowering Plants Class 12 Notes explained step by step, in simple English, with complete coverage of all topics.

Sexual Reproduction in Flowering Plants Class 12 Notes | NCERT Biology | Important Questions

1. Flower – The Reproductive Organ of Angiosperms

A flower is the reproductive structure of flowering plants (angiosperms). It is specially modified for sexual reproduction.

Structure of a Typical Flower

A typical flower has four main whorls arranged from outside to inside:

1. Calyx
   • Composed of sepals
   • Usually green in color
   • Protects the flower in the bud stage
2. Corolla
   • Composed of petals
   • Brightly colored
   • Attracts insects for pollination
3. Androecium (Male Reproductive Part)
   • Composed of stamens
4. Gynoecium (Female Reproductive Part)
   • Composed of carpels or pistil

2. Androecium – Male Reproductive Organ

The androecium consists of stamens, which are the male reproductive units of a flower.

Structure of a Stamen

Each stamen has two parts:

• Filament – Long slender stalk
• Anther – Terminal swollen part

Structure of Anther

• Anther is bilobed
• Each lobe has two pollen sacs
• Total four pollen sacs are present
• Pollen sacs contain pollen grains

3. Microsporogenesis

Microsporogenesis is the process by which microspores (pollen grains) are formed inside the anther.

Process:

• Each pollen sac contains Microspore Mother Cells (MMC)
• MMC undergoes meiosis
• Four haploid microspores are formed
• Each microspore develops into a pollen grain

4. Pollen Grain – Male Gametophyte

A pollen grain represents the male gametophyte.

Structure of Pollen Grain

It has two walls:

1. Exine
   • Outer thick wall
   • Made of sporopollenin
   • Highly resistant material
2. Intine
   • Inner thin wall
   • Made of cellulose and pectin

Cells in Pollen Grain

• Vegetative cell
• Generative cell (divides to form two male gametes)

5. Gynoecium – Female Reproductive Organ

The gynoecium is composed of one or more carpels.

Parts of Gynoecium

1. Stigma
   • Receives pollen grains
   • Sticky surface
2. Style
   • Slender stalk
   • Connects stigma to ovary
3. Ovary
   • Swollen basal part
   • Contains ovules

6. Ovule – Structure and Types

The ovule is the structure that develops into a seed after fertilization.

Structure of an Ovule

• Integuments – Protective layers
• Nucellus – Nutritive tissue
• Embryo sac – Female gametophyte
• Micropyle – Opening for pollen tube
• Chalaza – Basal part of ovule

7. Megasporogenesis

Megasporogenesis is the formation of megaspores from the Megaspore Mother Cell (MMC).

Process:

• MMC undergoes meiosis
• Four megaspores are formed
• Three degenerate
• One functional megaspore develops into embryo sac

8. Embryo Sac – Female Gametophyte

The embryo sac is the female gametophyte of flowering plants.

Structure:

It is 7-celled and 8-nucleate:

• Egg cell
• Two synergids
• Three antipodal cells
• Two polar nuclei

9. Pollination

Pollination is the transfer of pollen grains from anther to stigma.

Types of Pollination

1. Self Pollination
   • Autogamy – Same flower
   • Geitonogamy – Different flower, same plant
2. Cross Pollination (Xenogamy)
   • Between flowers of different plants

10. Agents of Pollination

Pollination can occur through different agents:

• Wind (Anemophily)
• Water (Hydrophily)
• Insects (Entomophily)
• Birds (Ornithophily)

11. Outbreeding Devices

Plants use outbreeding devices to prevent self-pollination:

• Dichogamy
• Herkogamy
• Self-incompatibility
• Unisexuality

12. Pollen-Pistil Interaction

After pollination:

• Pollen grain germinates
• Pollen tube grows through style
• Reaches ovule via micropyle

13. Double Fertilization

Double fertilization is a unique feature of angiosperms.

Two Types:

1. Syngamy
   • Male gamete + egg = Zygote
2. Triple Fusion
   • Male gamete + polar nuclei = Endosperm

14. Post-Fertilization Changes

• Zygote → Embryo
• Ovule → Seed
• Ovary → Fruit

15. Seed Structure

A seed consists of:

• Seed coat
• Embryo
• Endosperm (in some seeds)

16. Fruit Formation

Fruit develops from the ovary after fertilization.

Types:

• True fruit
• False fruit
• Parthenocarpic fruit

17. Apomixis

Apomixis is seed formation without fertilization.

18. Polyembryony

Formation of more than one embryo in a single seed.

Importance of Sexual Reproduction

• Produces genetic variation
• Helps in evolution
• Ensures survival of species

Conclusion

The chapter Sexual Reproduction in Flowering Plants Class 12 Notes is one of the most scoring units in Biology. If studied line by line from NCERT and understood conceptually, it can guarantee excellent marks in board exams and competitive exams like NEET. Regular revision, diagram practice, and understanding of processes like double fertilization are key to mastering this chapter.

Important Questions – Sexual Reproduction in Flowering Plants (Class 12)

⭐ Very Important (Repeated Every Year)

1️⃣ One Mark Questions (VSA)

These are most repeated in board exams:

1. What is double fertilization?
2. Name the outer and inner wall of a pollen grain.
3. Which tissue provides nutrition to the developing embryo?
4. What is sporopollenin?
5. Define pollination.
6. What is the function of stigma?
7. Name the opening through which pollen tube enters the ovule.
8. What is apomixis?
9. How many nuclei are present in a mature embryo sac?
10. What is polyembryony?

⭐⭐ Two Mark Questions (Short Answer)

11. What is microsporogenesis?
12. Write any two differences between autogamy and xenogamy.
13. Name any two agents of pollination and give one example each.
14. What is the function of synergids?
15. What is parthenocarpy?
16. Why is sporopollenin considered a resistant substance?
17. What is megasporogenesis?
18. What is pollen–pistil interaction?
19. Mention two outbreeding devices in flowering plants.
20. What is the role of endosperm?

⭐⭐⭐ Three Mark Questions (Frequently Asked)

21. Describe the structure of a pollen grain.
22. Explain the structure of a typical ovule.
23. Write any three differences between self-pollination and cross-pollination.
24. Describe the process of microsporogenesis.
25. Explain the structure of embryo sac.
26. What are outbreeding devices? Explain any three.
27. Describe post-fertilization changes in a flower.
28. Explain the development of pollen grain.

⭐⭐⭐⭐ Five Mark Questions (Most Repeated Long Answer)

⚠️ VERY IMPORTANT – Almost guaranteed questions

29. Describe double fertilization in flowering plants with a labeled diagram.
30. Explain the structure and development of a mature embryo sac.
31. Describe pollination, its types and agents.
32. Explain microsporogenesis and development of male gametophyte.
33. Describe megasporogenesis and formation of female gametophyte.
34. Explain the development of seed and fruit after fertilization.
35. What is apomixis? Explain its significance.
36. Describe polyembryony with suitable examples.

⭐ Diagram-Based Questions (High Scoring)

37. Draw a labeled diagram of:

• L.S. of flower
• Mature embryo sac
• Pollen grain
• Ovule

(⚠️ Diagrams are frequently asked in boards)

⭐ Assertion–Reason Questions (New Pattern)

38. Assertion: Double fertilization is unique to angiosperms.
    Reason: One male gamete fuses with egg and the other with polar nuclei.
39. Assertion: Wind-pollinated flowers produce large amount of pollen.
    Reason: Chances of pollen reaching stigma are very low.

⭐ NEET & MCQ Focus Questions

40. Which cell divides to form male gametes?
41. How many pollen sacs are present in an anther?
42. Functional megaspore develops into?
43. Entry of pollen tube into ovule occurs through?
44. Which hormone is related to parthenocarpy?

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