Fertilisation, Seed and Fruit Formation

What happens after pollination, and how a fertilised flower becomes a seed and fruit.

Fertilisation, Seed and Fruit Formation

After pollination, the pollen grain reaches the stigma and undergoes germination. The pollen tube then grows through the style and carries the male gametes towards the ovule. The events that follow pollination ultimately result in fertilisation, embryo development, seed formation and fruit formation.

In flowering plants, fertilisation is a highly organised process that takes place inside the embryo sac. A special feature of angiosperms is the occurrence of double fertilisation, in which two different fusion events take place in the same embryo sac.

Pollination के बाद reproductive process समाप्त नहीं होता। इसके बाद pollen germination, pollen tube growth, male gamete delivery, fertilisation, embryo development, endosperm formation और अंत में seed तथा fruit formation जैसी घटनाएँ क्रम से होती हैं।

1. Pollen Germination

When a compatible pollen grain lands on the stigma, it absorbs water and nutrients from the stigmatic surface and germinates.

The pollen grain produces a pollen tube through one of its germ pores. The pollen tube grows downward through the style towards the ovary.

In many angiosperms, the pollen tube carries two male gametes. These male gametes are ultimately released inside the embryo sac.

Pollen grain को एक delivery structure की तरह समझा जा सकता है। इसका मुख्य कार्य male gametes को embryo sac तक पहुँचाना है।

2. Growth of Pollen Tube

The pollen tube grows through the tissues of the stigma and style. Its growth is directed towards the ovary and subsequently towards an ovule.

The pollen tube usually enters the ovule through the micropyle. This type of entry is known as porogamy.

After entering the ovule, the pollen tube reaches the embryo sac and releases the two male gametes.

Important Terms

Term Meaning
Pollen tube Tube formed by germinating pollen grain for the transport of male gametes.
Micropyle Small opening in the ovule through which the pollen tube usually enters.
Porogamy Entry of pollen tube into the ovule through the micropyle.

3. Entry of Pollen Tube into the Embryo Sac

The pollen tube enters one of the synergids through the filiform apparatus present at its micropylar end.

The synergid helps in guiding the pollen tube towards the egg apparatus. After reaching the synergid, the pollen tube bursts and releases the two male gametes into the embryo sac.

One male gamete moves towards the egg, while the other moves towards the central cell containing the two polar nuclei.

Synergids का एक महत्वपूर्ण कार्य pollen tube को embryo sac के अंदर guide करना है। Pollen tube के प्रवेश के बाद इसके द्वारा दो male gametes release किए जाते हैं।

4. Fertilisation

Fertilisation is the fusion of male and female gametes resulting in the formation of a zygote.

In angiosperms, the male gametes are delivered to the embryo sac by the pollen tube.

The egg cell acts as the female gamete. One male gamete fuses with the egg to form a diploid zygote.

Male Gamete + Egg → Zygote (2n)

यह संलयन sexual reproduction की सबसे महत्वपूर्ण घटनाओं में से एक है, क्योंकि इसी से zygote बनता है और zygote आगे चलकर embryo में विकसित होता है।

5. Double Fertilisation

Double fertilisation is a characteristic feature of flowering plants. It involves two fusion events within the same embryo sac.

The two fusion events are:

  1. Syngamy
  2. Triple fusion

Since both events occur in the same embryo sac, the process is called double fertilisation.

Double fertilisation में दो अलग-अलग fusion होते हैं। पहला fusion egg के साथ होता है और दूसरा fusion two polar nuclei के साथ होता है।

6. Syngamy

Syngamy is the fusion of one male gamete with the egg.

The product of syngamy is a diploid zygote.

Male Gamete (n) + Egg (n) → Zygote (2n)

The zygote is the first cell of the new sporophytic generation.

Syngamy में केवल दो gametes का संलयन होता है—एक male gamete और एक egg। इसलिए इसका product zygote होता है और इसका chromosome number 2n होता है।

7. Triple Fusion

The second male gamete fuses with the two polar nuclei present in the central cell of the embryo sac.

This fusion is called triple fusion because three nuclei are involved in the fusion:

  • One male gamete nucleus
  • First polar nucleus
  • Second polar nucleus

The product is called the Primary Endosperm Nucleus (PEN).

Male Gamete (n) + Polar Nucleus (n) + Polar Nucleus (n) → PEN (3n)

Triple fusion के बाद बनने वाला Primary Endosperm Nucleus सामान्यतः triploid होता है, क्योंकि इसमें तीन haploid nuclei का genetic contribution होता है।

8. Syngamy and Triple Fusion

Feature Syngamy Triple Fusion
Participating nuclei Male gamete + Egg Male gamete + Two polar nuclei
Number of nuclei involved 2 3
Product Zygote Primary Endosperm Nucleus
Ploidy Diploid (2n) Triploid (3n)
Further development Embryo Endosperm

9. Why is Double Fertilisation Important?

Double fertilisation ensures the simultaneous formation of the embryo and endosperm.

The zygote develops into the embryo, while the Primary Endosperm Nucleus gives rise to the endosperm. The endosperm provides nourishment to the developing embryo.

इस प्रकार fertilisation के बाद embryo के विकास के लिए genetic starting point और nutritional tissue दोनों की व्यवस्था हो जाती है।

10. Post-Fertilisation Changes

After fertilisation, the flower undergoes several changes. The zygote develops into an embryo, while the fertilised ovule develops into a seed. The ovary develops into a fruit.

Structure Before / During Fertilisation Structure Developed After Fertilisation
Zygote Embryo
Primary Endosperm Nucleus Endosperm
Ovule Seed
Integuments Seed coat
Ovary Fruit
Ovary wall Pericarp
सबसे महत्वपूर्ण relationships: Zygote → Embryo, Ovule → Seed और Ovary → Fruit। इन्हें आपस में confuse नहीं करना चाहिए।

11. Development of Zygote

The zygote develops into an embryo. In many angiosperms, the zygote starts dividing only after a certain amount of endosperm formation.

This arrangement ensures that the developing embryo receives nourishment from the endosperm.

The zygote undergoes repeated cell divisions and differentiation to form the embryonal axis and cotyledons.

12. Embryo

An embryo is the young developing plant present inside the seed.

The basic structure of an embryo includes:

  • Embryonal axis
  • Cotyledons
  • Plumule
  • Radicle

Dicot embryos have two cotyledons, whereas monocot embryos have one cotyledon.

13. Dicot Embryo

A typical dicot embryo consists of two cotyledons and an embryonal axis.

The portion of the embryonal axis above the level of cotyledons is called the epicotyl, while the portion below the cotyledons is called the hypocotyl.

The epicotyl terminates in the plumule, which develops into the shoot system. The hypocotyl terminates in the radicle, which develops into the primary root.

Structure Function / Development
Cotyledons Embryonic leaves; may store food.
Embryonal axis Main axis of the developing embryo.
Epicotyl Part of embryonal axis above cotyledons.
Hypocotyl Part of embryonal axis below cotyledons.
Plumule Develops into the shoot system.
Radicle Develops into the primary root.

Dicot embryo में दो cotyledons होते हैं। Cotyledons के ऊपर shoot-related region और नीचे root-related region विकसित होता है। इसी कारण plumule को shoot तथा radicle को root से जोड़कर पढ़ना उपयोगी है।

14. Monocot Embryo

A typical monocot embryo has only one cotyledon. In grasses such as maize, this single cotyledon is called the scutellum.

The embryonal axis of a monocot embryo has the plumule and radicle at its opposite ends.

The plumule is protected by a sheath called the coleoptile, while the radicle is protected by a sheath called the coleorhiza.

Structure Function
Scutellum Single cotyledon of grass embryo.
Plumule Develops into shoot.
Radicle Develops into root.
Coleoptile Protective sheath around plumule.
Coleorhiza Protective sheath around radicle.

Monocot embryo में एक ही cotyledon होता है, जिसे grasses में scutellum कहते हैं। Coleoptile shoot की रक्षा करता है, जबकि coleorhiza root की रक्षा करता है।

15. Endosperm

The endosperm is a nutritive tissue that provides nourishment to the developing embryo.

It develops from the Primary Endosperm Nucleus formed as a result of triple fusion.

In most angiosperms, the Primary Endosperm Nucleus divides repeatedly and produces the endosperm.

The endosperm may be cellular, nuclear or helobial depending on the pattern of nuclear divisions and cell wall formation.

Examples of Endospermic Seeds

  • Wheat
  • Maize
  • Castor
  • Coconut

Endosperm developing embryo के लिए भोजन और पोषण का स्रोत है। कुछ seeds में mature अवस्था तक endosperm बचा रहता है, जबकि कुछ seeds में embryo के विकास के दौरान इसका अधिकांश भाग उपयोग हो जाता है।

16. Types of Seeds Based on Endosperm

Based on the presence or absence of endosperm in the mature seed, seeds can be broadly classified into albuminous and non-albuminous seeds.

Type Characteristics Examples
Albuminous / Endospermic Endosperm remains in the mature seed. Wheat, maize, castor, coconut
Non-albuminous / Non-endospermic Endosperm is consumed during embryo development. Pea, gram, bean

Albuminous seed में mature seed के अंदर endosperm मौजूद रहता है। Non-albuminous seed में embryo के विकास के दौरान endosperm का भोजन उपयोग हो जाने के कारण mature seed में endosperm बहुत कम या अनुपस्थित होता है।

17. Structure of a Seed

A typical seed consists of a seed coat and an embryo. In many seeds, endosperm is also present.

The main parts of a seed include:

  • Seed coat
  • Hilum
  • Micropyle
  • Embryo
  • Cotyledons
  • Endosperm, where present

18. Seed Coat

The integuments of the ovule develop into the seed coat after fertilisation.

The outer integument generally forms the testa, while the inner integument forms the tegmen.

Ovule Structure Seed Structure
Integuments Seed coat
Outer integument Testa
Inner integument Tegmen

19. Hilum

The hilum is a scar on the seed coat that represents the point of attachment of the seed to the funicle.

जब seed ovule से जुड़ा होता है, तब funicle के माध्यम से attachment रहता है। Seed mature होने के बाद attachment point पर दिखाई देने वाला scar hilum कहलाता है।

20. Micropyle in Seed

The micropyle is a small opening present in the seed coat. It represents the position of the micropyle of the original ovule.

The micropyle can facilitate the entry of water and gases during germination.

21. Fruit Formation

After fertilisation, the ovary develops into a fruit. The wall of the ovary develops into the pericarp.

Ovary → Fruit

Ovary Wall → Pericarp

The pericarp may be dry or fleshy depending on the type of fruit.

Fruit formation is generally associated with fertilisation, although fruits can also develop without fertilisation in certain cases.

22. True Fruit

A fruit that develops mainly from the ovary is called a true fruit.

Examples include tomato, mango and pea.

23. False Fruit or Accessory Fruit

A fruit in which parts of the flower other than the ovary also contribute significantly to fruit formation is called a false fruit or accessory fruit.

Apple is a common example of a false fruit. In apple, the thalamus contributes significantly to the edible part of the fruit.

True fruit में fruit का मुख्य विकास ovary से होता है, जबकि false fruit में ovary के अतिरिक्त floral parts भी fruit formation में योगदान देते हैं।

24. Parthenocarpy

Parthenocarpy is the development of fruit without fertilisation.

Parthenocarpic fruits are generally seedless because fertilisation does not occur and therefore normal seed development does not take place.

Example: Banana.

Parthenocarpy में fertilisation के बिना fruit बन जाता है। इसलिए ऐसे fruits में सामान्य seed development नहीं होता और कई बार फल seedless दिखाई देता है।

25. Significance of Seed

Seeds are important reproductive structures in flowering plants. They contain the embryo and, in many cases, stored food or endosperm required for early development.

Seeds also help plants survive unfavourable conditions and facilitate the dispersal of offspring to new locations.

26. Seed Dormancy

Seed dormancy is a condition in which a viable seed does not germinate even when some apparently favourable conditions are present.

Dormancy helps seeds survive unfavourable environmental conditions.

When appropriate environmental and physiological conditions are achieved, the dormant seed can resume growth and germinate.

Seed dormancy पौधे के लिए survival mechanism की तरह कार्य करती है। इससे seed प्रतिकूल परिस्थितियों में तुरंत germinate नहीं करता और अनुकूल समय आने तक सुरक्षित रह सकता है।

27. Seed Dispersal

Seed dispersal is the movement of seeds away from the parent plant.

Dispersal reduces competition between the parent plant and its offspring for resources such as light, water, minerals and space.

Seeds may be dispersed by:

  • Wind
  • Water
  • Animals
  • Explosive mechanisms of fruits

28. Complete Sequence of Events

The complete sequence from pollination to seed and fruit formation can be represented as follows:

  1. Pollination
  2. Pollen germination
  3. Pollen tube formation
  4. Pollen tube growth through the style
  5. Entry of pollen tube into the ovule
  6. Entry into the embryo sac
  7. Release of two male gametes
  8. Syngamy
  9. Triple fusion
  10. Zygote formation
  11. Primary Endosperm Nucleus formation
  12. Embryo development
  13. Endosperm development
  14. Ovule develops into seed
  15. Ovary develops into fruit
Concept Flow:
Pollination → Pollen germination → Pollen tube → Male gametes → Double fertilisation → Zygote + PEN → Embryo + Endosperm → Seed + Fruit

29. Important Transformation Table

Original Structure Post-Fertilisation Structure
Zygote Embryo
Primary Endosperm Nucleus Endosperm
Ovule Seed
Integuments Seed coat
Ovary Fruit
Ovary wall Pericarp
Egg + Male gamete Zygote
Two polar nuclei + Male gamete Primary Endosperm Nucleus

30. Important NCERT Terms

Term Definition
Fertilisation Fusion of male and female gametes.
Syngamy Fusion of male gamete with egg.
Triple fusion Fusion of male gamete with two polar nuclei.
Double fertilisation Occurrence of syngamy and triple fusion in the same embryo sac.
Zygote Diploid product of syngamy.
Primary Endosperm Nucleus Triploid nucleus formed after triple fusion.
Endosperm Nourishing tissue for the developing embryo.
Scutellum Single cotyledon of a grass embryo.
Coleoptile Protective sheath around the plumule in monocots.
Coleorhiza Protective sheath around the radicle in monocots.
Hilum Scar representing attachment of seed to funicle.
Parthenocarpy Development of fruit without fertilisation.
Pericarp Fruit wall derived from the ovary wall.
Albuminous seed Mature seed retaining endosperm.
Non-albuminous seed Mature seed in which endosperm is consumed during embryo development.

31. Board Important Questions

Very Short Answer Questions

  1. What is fertilisation?
  2. Define syngamy.
  3. What is triple fusion?
  4. What is double fertilisation?
  5. What is the ploidy of the zygote?
  6. What is the ploidy of the Primary Endosperm Nucleus?
  7. What does the ovule develop into?
  8. What does the ovary develop into?
  9. What is parthenocarpy?
  10. Give one example of a parthenocarpic fruit.
  11. What is scutellum?
  12. What is the function of coleoptile?
  13. What is the function of coleorhiza?
  14. What is hilum?
  15. What is endosperm?

Short Answer Questions

  1. Explain the process of double fertilisation in angiosperms.
  2. Differentiate between syngamy and triple fusion.
  3. Explain the development of endosperm.
  4. Describe the structure of a dicot embryo.
  5. Describe the structure of a monocot embryo.
  6. Differentiate between albuminous and non-albuminous seeds.
  7. Explain the post-fertilisation changes in a flower.
  8. What is parthenocarpy? Give an example.
  9. Differentiate between true fruit and false fruit.
  10. Explain the role of endosperm in seed development.

Long Answer Questions

  1. Describe the events that occur from pollination to fertilisation in flowering plants.
  2. Explain double fertilisation in angiosperms and describe the two fusion events involved in it.
  3. Describe the post-fertilisation changes that occur in a flower.
  4. Describe the structure of dicot and monocot embryos.
  5. Explain seed formation and describe albuminous and non-albuminous seeds.
  6. Describe the formation of fruit and distinguish between true and false fruits.

32. Multiple Choice Questions

  1. The fusion of male gamete with egg is called:

    • (A) Triple fusion
    • (B) Syngamy
    • (C) Pollination
    • (D) Germination

    Answer: (B) Syngamy

  2. The product of syngamy is:

    • (A) Endosperm
    • (B) Zygote
    • (C) Seed coat
    • (D) Pericarp

    Answer: (B) Zygote

  3. The chromosome number of the zygote is:

    • (A) n
    • (B) 2n
    • (C) 3n
    • (D) 4n

    Answer: (B) 2n

  4. Triple fusion results in the formation of:

    • (A) Zygote
    • (B) Embryo
    • (C) Primary Endosperm Nucleus
    • (D) Seed coat

    Answer: (C) Primary Endosperm Nucleus

  5. The Primary Endosperm Nucleus is generally:

    • (A) Haploid
    • (B) Diploid
    • (C) Triploid
    • (D) Tetraploid

    Answer: (C) Triploid

  6. After fertilisation, the ovule develops into:

    • (A) Fruit
    • (B) Seed
    • (C) Pericarp
    • (D) Endosperm

    Answer: (B) Seed

  7. After fertilisation, the ovary develops into:

    • (A) Seed
    • (B) Embryo
    • (C) Fruit
    • (D) Endosperm

    Answer: (C) Fruit

  8. The single cotyledon of a grass embryo is called:

    • (A) Coleoptile
    • (B) Coleorhiza
    • (C) Scutellum
    • (D) Plumule

    Answer: (C) Scutellum

  9. Coleoptile protects the:

    • (A) Radicle
    • (B) Plumule
    • (C) Cotyledon
    • (D) Endosperm

    Answer: (B) Plumule

  10. Coleorhiza protects the:

    • (A) Plumule
    • (B) Radicle
    • (C) Scutellum
    • (D) Cotyledon

    Answer: (B) Radicle

  11. Fruit development without fertilisation is known as:

    • (A) Syngamy
    • (B) Triple fusion
    • (C) Parthenocarpy
    • (D) Pollination

    Answer: (C) Parthenocarpy

  12. Which of the following is a false fruit?

    • (A) Mango
    • (B) Pea
    • (C) Apple
    • (D) Tomato

    Answer: (C) Apple

  13. The ovary wall develops into:

    • (A) Seed coat
    • (B) Pericarp
    • (C) Endosperm
    • (D) Embryo

    Answer: (B) Pericarp

  14. The integuments of the ovule develop into:

    • (A) Pericarp
    • (B) Endosperm
    • (C) Seed coat
    • (D) Embryo

    Answer: (C) Seed coat

  15. Which tissue provides nourishment to the developing embryo?

    • (A) Pericarp
    • (B) Endosperm
    • (C) Testa
    • (D) Tegmen

    Answer: (B) Endosperm

33. Fill in the Blanks

  1. Fusion of male gamete with egg is called __________.
  2. Fusion of male gamete with two polar nuclei is called __________.
  3. The product of syngamy is __________.
  4. The product of triple fusion is the __________.
  5. The ovule develops into a __________ after fertilisation.
  6. The ovary develops into a __________.
  7. The ovary wall develops into the __________.
  8. The single cotyledon of a grass embryo is called __________.
  9. The sheath protecting the plumule is called __________.
  10. The sheath protecting the radicle is called __________.
  11. Fruit development without fertilisation is called __________.
  12. The scar representing attachment of seed to funicle is called __________.

Answers: Syngamy, Triple fusion, Zygote, Primary Endosperm Nucleus, Seed, Fruit, Pericarp, Scutellum, Coleoptile, Coleorhiza, Parthenocarpy, Hilum.

34. Match the Following

Column A Column B
1. Syngamy a. Fruit
2. Triple fusion b. Zygote
3. Ovule c. Primary Endosperm Nucleus
4. Ovary d. Seed
5. Coleoptile e. Protects plumule
6. Coleorhiza f. Protects radicle
7. Scutellum g. Single cotyledon

Answers: 1-b, 2-c, 3-d, 4-a, 5-e, 6-f, 7-g.

35. Quick Revision

  • Pollination is followed by pollen germination and pollen tube growth.
  • The pollen tube usually enters the ovule through the micropyle.
  • The pollen tube enters the embryo sac through a synergid.
  • Two male gametes are released inside the embryo sac.
  • One male gamete fuses with the egg. This is called syngamy.
  • Syngamy produces a diploid zygote.
  • The second male gamete fuses with two polar nuclei. This is called triple fusion.
  • Triple fusion produces the triploid Primary Endosperm Nucleus.
  • Syngamy + Triple fusion = Double fertilisation.
  • Zygote develops into embryo.
  • Primary Endosperm Nucleus develops into endosperm.
  • Ovule develops into seed.
  • Integuments develop into seed coat.
  • Ovary develops into fruit.
  • Ovary wall develops into pericarp.
  • Dicot embryo has two cotyledons.
  • Monocot embryo has one cotyledon.
  • In grasses, the cotyledon is called scutellum.
  • Coleoptile protects plumule.
  • Coleorhiza protects radicle.
  • Fruit formation without fertilisation is called parthenocarpy.
  • Apple is a common example of a false fruit.
Most Important Relationships for Examination

Male Gamete + Egg → Zygote (2n)

Male Gamete + Two Polar Nuclei → PEN (3n)

Zygote → Embryo

PEN → Endosperm

Ovule → Seed

Ovary → Fruit

Ovary Wall → Pericarp

Lesson 2 of 24
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