Post Fertilization - Events And Changes In Flowering Plants

Edited By Irshad Anwar | Updated on Jul 02, 2025 07:09 PM IST

Fertilization In Flowering Plants

Fertilization in flowering plants is the process by which male and female gametes fuse to form a zygote.

Description Of Fertilization Process

The fertilization process is described below:

Pollination

Self-pollination: This is the transfer of pollen from anther to the stigma of the same flower, or different flower of the same plant.
Cross-pollination: This is the transfer of pollen from the anther of one plant to another plant's stigma.

Double Fertilization

A pollen grain lands on the stigma, germinates and produces a pollen tube.
The pollen tube grows down the style and into the ovary to the ovule.
One sperm combines with an egg cell to form a zygote (2n).
The other sperm combines with two polar nuclei to form the triploid endosperm (3n).

Post-Fertilization Changes

Such post-fertilization changes in a flower are 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 Zygote

Mitotic division of the zygote forms the embryo.

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Endosperm Development

The triploid cell divides to nourish the developing embryo.

Seed Development

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

Zygote To Embryo Stages

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.

Development Of Seed Coat

The zygote's developmental series goes through a couple of stages of development that eventually lead up to seed formation.

Zygote To Embryo Development Stages

The development stages are given below:

Proembryo Stage

Initial cell divisions of the zygote.

Globular Stage

The embryo develops into a sphere.

Heart Stage

The embryo takes on a heart-like shape as cotyledons develop.

Torpedo Stage

Further elongation and differentiation of the embryo.

Seed Coat Formation

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

Maturation Of Seed

The accumulation of nutrients.
Seeds become dehydrated and their coats harden.

Endosperm Formation

The endosperm develops after fertilization and serves to nourish the embryo.

Endosperm Type

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.

Role Of The Endosperm In Seed Development

Supplies nutrition to the developing embryo.

Development Of The Fruit

The ovary becomes a fruit, which serves to protect and disperse the seed.

Transformation Of The Ovary Into Fruit

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).

Hormones And Fruit Development

Auxins: Stimulate cell elongation.
Gibberellins: Promote growth and development.
Cytokinins: Stimulate cell division.

Methods Of Seed Dispersal

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, for example, touch-me-not.

Seed Adaptations For Various Means Of Dispersal

Special structures such as wings or flotation organs.

Role Of Seed Dispersal In Plant Reproduction

Spreads plants out, reduces competition, and enhances colonization of new locations.

Seed Dormancy And Germination

Dormancy provides for seed survival during adverse conditions until the seed germinates.
A resting or quiescent state of metabolic inactivity.

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.

Process Of Seed Germination

Imbibition: Water uptake by the seed.
Activation of Enzymes: Stored nutrients are hydrolysed by enzymes.
Radicle and Plumule Emergence: Root and shoot development.

Favourable Conditions For Germination

Correct Temperature, water, oxygen, and light.
Environment plays an essential role in determining changes after fertilisation and the process of seed development.
Action of Temperature, Water, Light, and Soil on Changes after Fertilisation
Appropriate environmental conditions are required for the development of seeds and fruits.
Effects of Biotic Factors, for example, Pests, Pollinators
Biotic interactions can affect fertilization, seed development as well as dispersal.

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Frequently Asked Questions (FAQs)

1. What are the changes after fertilization in flowering plants?

The post-fertilization changes are the following: from the zygote, an embryo develops; the endosperm forms and the seed and fruit mature.

2. How is the endosperm developed after fertilization?

The endosperm develops from the triploid cell resulting from double fertilization, providing nutrients to the developing embryo.

3. What are the steps of seed development in flowering plants?

Seed development in flowering plants occurs through stages: proembryo stage, globular stage, heart stage, torpedo stage

4. How do environmental factors affect post-fertilization events?

The overall success of fertilization, seed development, and germination is influenced by factors such as temperature, water, light, and soil conditions.

5. How do environmental factors affect post-fertilization events?

Environmental factors can significantly impact post-fertilization events:

6. What are the various modes of seed dispersal?

Seed dispersal occurs through wind, water, animals, and mechanical means. All of these have some adaptations that assist in their effective dispersal.

7. How do seedless fruits develop, and what implications does this have for reproduction?

Seedless fruits can develop through several mechanisms:

8. Why is the endosperm important for seed development?

The endosperm is crucial for seed development because it serves as a nutrient-rich tissue that supports the growing embryo. It provides energy and nutrients for the developing plant until it can produce its own food through photosynthesis. In some plants, the endosperm persists in mature seeds (like in corn), while in others, it's absorbed by the embryo during development (like in beans).

9. How do different types of endosperm development affect seed structure?

There are three main types of endosperm development:

10. How does the maternal plant influence seed development?

The maternal plant influences seed development in several ways:

11. How do seed storage compounds accumulate during seed development?

Seed storage compounds accumulate through complex biosynthetic pathways:

12. What is programmed cell death in seed development, and why does it occur?

Programmed cell death (PCD) is a genetically controlled process of cell elimination that occurs during seed development. It's important for:

13. What is double fertilization in flowering plants?

Double fertilization is a unique process in flowering plants where two sperm cells from a pollen grain fertilize two different cells in the ovule. One sperm fertilizes the egg cell to form the zygote, while the other fuses with two polar nuclei to form the endosperm. This process ensures the development of both the embryo and its nutritive tissue.

14. How do fruits contribute to seed dispersal after fertilization?

Fruits play a crucial role in seed dispersal by:

15. How do symbiotic relationships affect post-fertilization events in some plants?

Symbiotic relationships can influence post-fertilization events:

16. How does fruit development relate to seed development?

Fruit development is closely linked to seed development. After fertilization, hormonal changes trigger the ovary to develop into a fruit. As the seeds develop inside, the fruit grows and matures. The fruit provides protection for the developing seeds and often aids in seed dispersal. The type and structure of the fruit are determined by the specific adaptations of the plant species for seed protection and dispersal.

17. What is the importance of seed banks in plant conservation, and how do they relate to post-fertilization events?

Seed banks are crucial for plant conservation because they:

18. How do epigenetic changes during seed development affect plant characteristics?

Epigenetic changes during seed development can have significant effects:

19. What is the role of calcium signaling in post-fertilization events?

Calcium signaling plays crucial roles in post-fertilization events:

20. What is apomixis, and how does it differ from sexual reproduction in flowering plants?

Apomixis is a form of asexual reproduction in plants where seeds are produced without fertilization. It differs from sexual reproduction in several ways:

21. How do genetic factors influence post-fertilization events?

Genetic factors play a significant role in post-fertilization events:

22. What is the difference between albuminous and exalbuminous seeds?

The main difference lies in the presence of endosperm in mature seeds:

23. What is the role of cell wall modifications in seed development?

Cell wall modifications play several important roles in seed development:

24. How does the zygote develop into an embryo?

After fertilization, the zygote undergoes a series of cell divisions (mitosis) and differentiation. It first divides asymmetrically to form a smaller apical cell and a larger basal cell. The apical cell develops into the embryo proper, while the basal cell forms the suspensor, which anchors the embryo and aids in nutrient transfer. The embryo then develops cotyledons, a radicle (embryonic root), and a plumule (embryonic shoot).

25. What is the significance of the suspensor in embryo development?

The suspensor plays a crucial role in early embryo development by:

26. How does the ovule transform into a seed?

The ovule transforms into a seed through several changes:

27. What is polyembryony, and how does it occur?

Polyembryony is the development of multiple embryos within a single seed. It can occur through several mechanisms:

28. What are the main types of embryo development patterns in flowering plants?

There are three main types of embryo development patterns in flowering plants:

29. What is seed dormancy, and why is it important?

Seed dormancy is a state in which seeds are unable to germinate even under favorable conditions. It's important because it:

30. How do seeds acquire desiccation tolerance?

Seeds acquire desiccation tolerance through several mechanisms:

31. What is the role of plant hormones in post-fertilization events?

Plant hormones play crucial roles in coordinating post-fertilization events:

32. What is seed coat development, and why is it important?

Seed coat development involves the transformation of ovule integuments into a protective layer around the seed. It's important because:

33. What is vivipary, and how does it differ from normal seed development?

Vivipary is a phenomenon where seeds germinate while still attached to the parent plant. It differs from normal seed development in several ways:

34. What is seed priming, and how does it relate to post-fertilization events?

Seed priming is a technique that partially hydrates seeds to initiate metabolic processes associated with germination, without allowing full germination. It relates to post-fertilization events by:

35. How do seed storage proteins differ from other plant proteins, and why are they important?

Seed storage proteins are specialized proteins that:

36. What is the significance of seed size variation in plant reproduction strategies?

Seed size variation is significant because it reflects different reproductive strategies:

37. How do environmental stresses during seed development affect seed quality and plant fitness?

Environmental stresses during seed development can have significant impacts:

38. What is seed coat-imposed dormancy, and how does it develop?

Seed coat-imposed dormancy is a type of physical dormancy where the seed coat prevents water uptake or gas exchange. It develops through:

39. How do seed dispersal mechanisms influence post-fertilization development?

Seed dispersal mechanisms can influence post-fertilization development in several ways: