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Post-Fertilisation: Endosperm, Embryo, Seed and Fruit

Post-fertilisation events are the changes after double fertilisation in which the primary endosperm nucleus forms endosperm, the zygote forms embryo, ovule becomes seed, and ovary becomes fruit.

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Student-friendly explanation

After fertilisation, the primary endosperm nucleus usually divides before the zygote develops actively, so nourishment is available for the embryo. Endosperm may remain free-nuclear for a time or become cellular. The zygote develops into an embryo with embryonal axis and cotyledons. In dicots, two cotyledons are present; in monocots, one cotyledon is present. The ovule develops into a seed, integuments form seed coats, and the ovary wall forms the pericarp of the fruit. In true fruits, the ovary mainly forms the fruit, while in false fruits other floral parts also contribute.

How to write this in exams

  1. 1

    Start with the exact idea

    Post-fertilisation events are the changes after double fertilisation in which the primary endosperm nucleus forms endosperm, the zygote forms embryo, ovule becomes seed, and ovary becomes fruit.

  2. 2

    Then show how to use it

    1. Double fertilisation produces zygote and primary endosperm nucleus. 2. Primary endosperm nucleus divides to form endosperm. 3. Zygote develops into embryo. 4. Embryo differentiates into embryonal axis and cotyledons. 5. Integuments harden into seed coats. 6. Ovule matures into seed. 7. Ovary wall forms pericarp and ovary matures into fruit. 8. Other floral parts may contribute in false fruits.

  3. 3

    Add one concrete example

    Coconut water represents free-nuclear endosperm, while the white kernel represents cellular endosperm. Apple is commonly cited as a false fruit because the thalamus contributes to the edible part.

  4. 4

    Avoid this incomplete answer

    A frequent wrong answer is saying endosperm always disappears before seed maturity. In some seeds it is consumed, while in others it persists.

Definition

Post-fertilisation events are the changes after double fertilisation in which the primary endosperm nucleus forms endosperm, the zygote forms embryo, ovule becomes seed, and ovary becomes fruit.

Example

Coconut water represents free-nuclear endosperm, while the white kernel represents cellular endosperm. Apple is commonly cited as a false fruit because the thalamus contributes to the edible part.

Rule to remember

Conversion rule: zygote forms embryo; primary endosperm nucleus forms endosperm; integuments form seed coat; ovule forms seed; ovary wall forms pericarp; ovary forms fruit.

Memory hook

Zygote to embryo, ovule to seed, ovary to fruit.

Examples and method

Worked example

If asked what happens to integuments after fertilisation, answer that they become seed coats. If asked what the ovary wall becomes, answer pericarp.

Method to apply

1. Double fertilisation produces zygote and primary endosperm nucleus. 2. Primary endosperm nucleus divides to form endosperm. 3. Zygote develops into embryo. 4. Embryo differentiates into embryonal axis and cotyledons. 5. Integuments harden into seed coats. 6. Ovule matures into seed. 7. Ovary wall forms pericarp and ovary matures into fruit. 8. Other floral parts may contribute in false fruits.

Diagram support

Label dicot embryo parts such as cotyledons, plumule, radicle, hypocotyl, epicotyl, and seed coat; for monocot embryo label scutellum, coleoptile, coleorhiza, plumule, radicle, and endosperm.

How CBSE asks it

Questions may ask for post-fertilisation changes, differences between dicot and monocot embryo, true and false fruit, or free-nuclear and cellular endosperm examples.

Avoid common mistakes

Common confusion

Students often write that the ovule becomes fruit and ovary becomes seed. The correct relation is ovule to seed and ovary to fruit.

Common wrong answer

A frequent wrong answer is saying endosperm always disappears before seed maturity. In some seeds it is consumed, while in others it persists.

Exam tip

For post-fertilisation answers, present changes as paired conversions: zygote to embryo, primary endosperm nucleus to endosperm, ovule to seed, ovary to fruit.

Quick check

What is the difference between seed formation and fruit formation after fertilisation?

The seed develops from the ovule, while the fruit develops from the ovary. The seed contains the embryo, and the fruit protects and helps in dispersal of seeds.

Answer writing and exam use

1-mark answer

Start with double fertilisation products, list the fate of zygote and primary endosperm nucleus, then write ovule to seed, integuments to seed coat, ovary wall to pericarp, and ovary to fruit with one example.

2-mark answer

Start with double fertilisation products, list the fate of zygote and primary endosperm nucleus, then write ovule to seed, integuments to seed coat, ovary wall to pericarp, and ovary to fruit with one example.

3-mark answer

Start with double fertilisation products, list the fate of zygote and primary endosperm nucleus, then write ovule to seed, integuments to seed coat, ovary wall to pericarp, and ovary to fruit with one example.
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