Post Fertilization - Events And Changes In Flowering Plants

What Are Post-Fertilization Changes?

The post-fertilization changes are the changes that occur after a flower is necessary for the formation of seed and fruit. This is a continuous process that finally propagates to the perpetuation of the plant life cycle.

Development of the Zygote (Embryogenesis)

Mitotic division of the zygote forms the embryo. The stages are described below:

1. Proembryo Stage: Initial divisions of the zygote.

2. Globular Stage: The embryo becomes spherical.

3. Heart Stage: The embryo becomes heart-shaped as cotyledons develop

4. Torpedo Stage: Additional elongation and differentiation of the embryo.

5. Mature embryo: radicle, plumule, cotyledons are fully developed

Endosperm Formation (3 Types)

The triploid cell divides to nourish the developing embryo. The endosperm develops after fertilization and serves to nourish the embryo.

Types of Endosperm

• Nuclear: Free nuclear divisions followed by cell wall formation.

• Cellular: Cell wall formation coincides with nuclear divisions.

• Helobial: A fusion of nuclear and cellular types.

Seed Development and Maturation

The sequence from the development of the zygote to the embryo brings about seed formation.

Seed Coat Formation

• The protective outer layers develop from the integuments of the ovule.

• It is the hard protective layer.

Nutrient Storage

• Endosperm or cotyledons accumulate food.

• Water scarcity or dehydration can lead to dormancy

Seed Components

• Seed coat

• Cotyledons

• Embryo (radicle, plumule)

• Endosperm

Fruit Development (From Ovary to Fruit)

The ovary becomes a fruit, which serves to protect and disperse the seed. The ovary wall thickens and differentiates into pericarp layers.

Types Of Fruits

• Simple Fruits: Derived from a single ovary (e.g. cherry).

• Aggregate Fruits: Originate from several ovaries of one flower (e.g. raspberry).

• Multiple Fruits: Originate from ovaries of several flowers (e.g. pineapple).

Hormonal Control of Fruit Development

Major hormones involved in the development of fruit are:

• Auxins: Stimulate cell elongation.

• Gibberellins: Promote growth and development.

• Cytokinins: Stimulate cell division.

Seed Dispersal Mechanisms

Seed dispersal mechanisms contribute to the distribution of seeds for species propagation.

Wind

Seeds are light enough to become airborne (e.g. dandelion).

Water

Seeds are buoyant and distributed by water (e.g. coconut).

Animals

Seeds have either barbs or an attached nutritious reward to attract animals that disperse them (e.g. burs, berries).

Mechanical

Explosive release, i.e., fruits bursts open, for example, touch-me-not.

Seed Dormancy

Dormancy provides for seed survival during adverse conditions until the seed germinates.

Factors That Affect Dormancy

• Temperature: Low temperatures can initiate dormancy.

• Moisture: Amount of available water impact.

• Light: Some seeds require the action of particular light intensity to end dormancy.

Seed Germination Process

A resting or quiescent state of metabolic inactivity.

Steps

• Imbibition is the Water uptake by the seed.

• Stored nutrients are hydrolysed by enzymes.

• Radicle and plumule emergence i.e., root and shoot development.

Conditions Required

• Correct Temperature,

• Water

• Oxygen

• Light (species-specific)

Environmental Factors Affecting Post-Fertilization Changes

The environment plays an essential role in determining changes after fertilisation and the process of seed development.

• Temperature, water, light, and soil changes after fertilisation

• Appropriate environmental conditions are required for the development of seeds and fruits.

• Effects of biotic factors, for example, pests and pollinators

• Biotic interactions can affect fertilization, seed development as well as dispersal.

Post fertilization NEET MCQs (With Answers & Explanations)

Important topics for NEET are:

• Endosperm and its types

• Seed dispersal mechanism

• Hormonal control for fruit development

Practice Questions for NEET

Q1. The radical and root cap of the embryonal axis is encased in a ________ sheath, which is an undifferentiated sheath.

1. Coleorhiza sheath

2. Scutellum sheath

3. Epicotyl sheath

4. None of the above

Correct answer: 1) Coleorhiza sheath

Explanation:

In some plants, particularly monocots like grasses, the radical (the embryonic root) and the root cap of the embryonal axis are encased in a protective structure called the coleorrhiza. The coleorrhiza is an undifferentiated sheath that surrounds and protects the radical and root cap during the early stages of germination. It helps the seedling by protecting the sensitive root tissues as they begin to grow through the seed coat and into the soil. Once the root system develops, the coleorrhiza typically degenerates.

Hence, the correct answer is option 1) Coleorhiza Sheath

Q2. The growing embryo receives nutrition in the form of _________ from reserve food materials found in the cells of endosperm tissue.

1. Starch

2. Glucose

3. Carbohydrate

4. Protein

Correct answer: 1) Starch

Explanation:

In the process of developing into a seed, the endosperm is a type of tissue found in the seeds of flowering plants. The cells of endosperm tissue contain reserve food components. It gives starch-based sustenance to the growing embryo. There are three different categories for endosperm development.

Hence, the correct answer is option 1) Starch.

Q3. Which of the following is post fertilisation event

1. Gamete formation

2. Gamete transfer

3. Gertilisation

4. Embryogenesis

Correct answer: 4) Embryogenesis

Explanation:

Post-fertilization events are those in sexual reproduction that occur after fertilization. Each sexually reproducing organism develops a diploid zygote following fertilization. Embryogenesis refers to the process of an embryo's development from a zygote. Therefore, "Embryogenesis" is the right response.

Hence, the correct answer is option 4) Embryogenesis.

Also Read:

• MCQs on Post fertilization

• Double Fertilization

• Abiotic Factors of Pollination

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