Post-fertilisation Structures and Events — Revision Notes

⚡ 30-Second Revision

**Ovule $\rightarrow$ Seed**
**Ovary $\rightarrow$ Fruit**
**Integuments $\rightarrow$ Seed Coat (Testa, Tegmen)**
**Ovary Wall $\rightarrow$ Pericarp**
**Zygote ($2n$) $\rightarrow$ Embryo ($2n$)**
**Primary Endosperm Nucleus (PEN, $3n$) $\rightarrow$ Endosperm ($3n$)**
**Nucellus ($2n$) $\rightarrow$ Perisperm (if persistent, e.g., black pepper)**
Endosperm Types — Nuclear (free nuclei), Cellular (walls form), Helobial (intermediate).
Seed Types — Albuminous (endosperm present, e.g., castor, maize), Non-albuminous (endosperm absent, food in cotyledons, e.g., pea, bean).
Fruit Types — True (from ovary only, e.g., mango), False (other floral parts, e.g., apple, strawberry), Parthenocarpic (seedless, without fertilisation, e.g., banana).

2-Minute Revision

Post-fertilisation events are the transformations that occur in a flower after successful double fertilisation, leading to the formation of seeds and fruits. The ovule matures into a seed, and the ovary develops into a fruit.

The zygote, formed by syngamy, develops into the embryo, which is the future plant. The primary endosperm nucleus (PEN), formed by triple fusion, develops into the endosperm, a nutritive tissue for the embryo.

Endosperm development can be nuclear (free nuclear divisions), cellular (immediate cell wall formation), or helobial (intermediate). The integuments of the ovule form the protective seed coat, while the ovary wall becomes the pericarp (fruit wall).

Seeds are classified as albuminous if they retain endosperm (e.g., castor, maize) or non-albuminous if the endosperm is consumed and food is stored in cotyledons (e.g., pea, bean). Fruits are true if they develop solely from the ovary (e.

g., mango) or false if other floral parts contribute (e.g., apple, strawberry). Parthenocarpic fruits develop without fertilisation and are typically seedless (e.g., banana). These events are crucial for plant propagation and dispersal.

5-Minute Revision

Post-fertilisation events are the culmination of sexual reproduction in flowering plants, initiated by double fertilisation. This process involves the transformation of the fertilised ovule into a seed and the ovary into a fruit.

The zygote ($2n$), resulting from syngamy, undergoes embryogeny to form the embryo. This development typically follows stages like proembryo, globular, heart-shaped, and mature embryo, with distinct features in dicots (two cotyledons) and monocots (single scutellum, coleoptile, coleorhiza).

The primary endosperm nucleus (PEN, $3n$), formed by triple fusion, develops into the endosperm, which provides nutrition to the growing embryo. Endosperm development can be nuclear (free nuclear divisions, e.

g., coconut water), cellular (immediate cell wall formation, e.g., Petunia), or helobial (intermediate). The integuments of the ovule harden to form the protective seed coat (testa and tegmen), while the ovary wall differentiates into the pericarp, the fruit wall.

Seeds are categorized as albuminous (endospermic) if they retain endosperm in maturity (e.g., castor, maize) or non-albuminous (exalbuminous) if the endosperm is fully consumed and food is stored in cotyledons (e.

g., pea, bean). Some seeds may also retain remnants of the nucellus as perisperm (e.g., black pepper). Fruits are classified based on their origin: true fruits develop only from the ovary (e.g., mango), while false fruits incorporate other floral parts like the thalamus (e.

g., apple, strawberry). Parthenocarpy is the development of seedless fruits without fertilisation (e.g., banana), which can be natural or induced. These transformations are vital for protecting the embryo, providing nourishment, and facilitating seed dispersal, ensuring the continuity of the plant species.

Prelims Revision Notes

Post-fertilisation Structures and Events: NEET Quick Recall

I. Key Transformations:

Ovule — $\rightarrow$ Seed
Ovary — $\rightarrow$ Fruit
Integuments — $\rightarrow$ Seed Coat (Outer: Testa, Inner: Tegmen)
Ovary Wall — $\rightarrow$ Pericarp (Fruit wall)
Zygote ($2n$) — $\rightarrow$ **Embryo ($2n$)**
Primary Endosperm Nucleus (PEN, $3n$) — $\rightarrow$ **Endosperm ($3n$)**
Nucellus ($2n$) — $\rightarrow$ Perisperm (if persistent, e.g., Black Pepper, Beet)
Funicle — $\rightarrow$ Stalk of seed
Micropyle — $\rightarrow$ Micropyle of seed (for water/gas exchange)

II. Endosperm Development:

Function — Nourishment for developing embryo.
Types

* Nuclear: Free nuclear divisions, then cell walls (e.g., Coconut water, Maize). * Cellular: Cell wall formation after each nuclear division (e.g., Petunia, Datura). * Helobial: First division forms wall, then free nuclear in chambers (e.g., Asphodelus).

III. Embryo Development (Embryogeny):

Zygote divides only after some endosperm formation.
Dicot Embryo — Zygote $\rightarrow$ Proembryo $\rightarrow$ Globular $\rightarrow$ Heart-shaped $\rightarrow$ Mature embryo (Plumule, Radicle, 2 Cotyledons, Hypocotyl, Epicotyl).
Monocot Embryo — Single cotyledon (Scutellum), Plumule covered by Coleoptile, Radicle covered by Coleorhiza.

IV. Seed Structure and Types:

Parts — Seed coat, Hilum, Micropyle, Embryo.
Albuminous (Endospermic) Seeds — Endosperm persists (e.g., Castor, Maize, Wheat, Coconut).
Non-albuminous (Exalbuminous) Seeds — Endosperm consumed, food in cotyledons (e.g., Pea, Bean, Groundnut).

V. Fruit Development and Types:

Pericarp — Fruit wall (Epicarp, Mesocarp, Endocarp).
True Fruits — Develop only from ovary (e.g., Mango, Tomato, Pea).
False Fruits (Accessory Fruits) — Other floral parts contribute (e.g., Apple, Pear, Strawberry - thalamus; Cashew - pedicel).
Parthenocarpic Fruits — Develop without fertilisation, typically seedless (e.g., Banana, Seedless Grapes). Can be natural or induced.

VI. Ploidy Levels (Crucial for NEET):

Egg cell: $n$
Male gamete: $n$
Zygote: $2n$
Central cell: $2n$
Primary Endosperm Nucleus (PEN): $3n$
Endosperm: $3n$
Embryo: $2n$
Nucellus: $2n$
Integuments: $2n$
Synergids: $n$
Antipodals: $n$

Vyyuha Quick Recall

To remember the fate of floral parts after fertilisation:

Old Ovaries Form Fruits. Old Ovules Start Seeds. Inner Integuments Turn To Tegmen. Outer Integuments Turn To Testa. Zygotes Evolve Embryos. PEN Ends Endosperm.