Post Fertilization - Events And Changes In Flowering Plants
Post-fertilisation events in flowering plants are essential for seed and fruit formation. After fertilisation, the zygote develops into an embryo, the endosperm provides nutrition, and the ovule matures into a seed. The ovary changes into a fruit. These post-fertilisation changes are essential for reproduction, dispersal, and survival of angiosperms. They form a core NEET topic under plant reproduction, covering seed formation, embryo stages, and fruit growth.
This Story also Contains
- Introduction to Post-Fertilisation Events
- Embryo Development in Flowering Plants (Embryogenesis)
- Endosperm Formation and Its Types
- Seed Development and Maturation
- Fruit Development in Angiosperms (From Ovary to Fruit)
- Seed Dispersal Mechanisms
- Seed Dormancy and Germination
- Environmental Factors Affecting Post-Fertilisation Events
- Post fertilisation NEET MCQs (With Answers & Explanations)
- Recommended Video On 'Post Fertilisation - Events And Changes In Flowering Plants'
In flowering plants, post-fertilisation events include embryogenesis, endosperm formation, seed dormancy, and fruit development. Each stage plays a vital role in Sexual Reproduction In Flowering Plants. These changes ensure proper nourishment, protection, and dispersal of the future plant. Exam questions often focus on embryo stages, types of endosperm, seed germination, and fruit classification. Mastering these concepts ensures better accuracy and confidence in competitive exams.
Introduction to Post-Fertilisation Events
Post-fertilisation events in flowering plants are the changes that occur after the fusion of male and female gametes. These changes are essential for the formation of seeds and fruits, which ensure the reproduction and survival of angiosperms.
The zygote develops into an embryo, the endosperm provides nourishment, and the ovule matures into a seed. Simultaneously, the ovary transforms into a fruit. These post-fertilisation changes are continuous processes that maintain the plant life cycle. They guarantee propagation, dispersal, and genetic continuity.
Embryo Development in Flowering Plants (Embryogenesis)
Embryogenesis in flowering plants begins with the zygote formed after fertilisation. The zygote undergoes mitotic divisions to form the embryo. The stages are described below:
Proembryo Stage: Initial divisions of the zygote.
Globular Stage: The embryo becomes spherical.
Heart Stage: The embryo becomes heart-shaped as cotyledons develop
Torpedo Stage: Additional elongation and differentiation of the embryo.
Mature embryo: radicle, plumule, and cotyledons are fully developed
Endosperm Formation and Its Types
The triploid cell divides to nourish the developing embryo. The endosperm develops after fertilisation 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
Seed development in flowering plants begins after fertilisation when the zygote develops into an embryo. This process leads to the formation of a mature seed, which ensures the reproduction and survival of the species.
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 in Angiosperms (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. The significance of seeds and fruit formation lies in ensuring protection, nourishment, dispersal, and continuity of plant species across generations.
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 the 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 burst open, for example, touch-me-not.
Seed Dormancy and Germination
Seed dormancy in flowering plants is a protective mechanism that allows seeds to survive during adverse conditions. Seed dormancy ensures that germination occurs only when the environment is favourable, preventing wastage of resources.
Factors That Affect Dormancy
Temperature: Low temperatures can initiate dormancy.
Moisture: The amount of available water impacts.
Light: Some seeds require the action of particular light intensity to end dormancy.
Seed Germination Process
Seed germination in flowering plants is the transition from a resting seed to an actively growing plant. A seed remains in a quiescent state with low metabolic activity until favourable conditions trigger germination. Steps are -
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- External factors necessary for successful seed germination.
Adequate water for imbibition
Correct temperature for enzyme activity
Sufficient oxygen for respiration
Light requirement varies with species
Environmental Factors Affecting Post-Fertilisation Events
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 fertilisation, seed development, and dispersal.
Post fertilisation 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.
Coleorhiza sheath
Scutellum sheath
Epicotyl sheath
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.
Starch
Glucose
Carbohydrate
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
Gamete formation
Gamete transfer
Gertilisation
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.
Recommended Video On 'Post Fertilisation - Events And Changes In Flowering Plants'
Frequently Asked Questions (FAQs)
The post-fertilization changes are the following: from the zygote, an embryo develops; the endosperm forms and the seed and fruit mature.
The endosperm develops from the triploid cell resulting from double fertilization, providing nutrients to the developing embryo.
Seed development in flowering plants occurs through stages: proembryo stage, globular stage, heart stage, torpedo stage
Seed dispersal occurs through wind, water, animals, and mechanical means. All of these have some adaptations that assist in their effective dispersal.
