Post Fertilisation - Events in Flowering Plants: Structures And Events
Post-fertilisation events in the plants start after the fusion of male and female gametes and form the zygote. The zygote performs mitosis to form the embryo, which grows into a new adult. While the embryo forms, the already formed triploid primary endosperm nucleus forms the endosperm. Post-fertilisation events are one of the important events of reproduction.
This Story also Contains
- What are Post-Fertilisation Events?
- Formation of the Zygote
- Endosperm Development
- Embryo Development
- Formation of Seed and Fruit
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The endosperm is the nutritional centre for the growing embryo. The seed is formed from the ovule and contains the embryo, endosperm, and a seed coat. The ovary forms the fruit, helping in the protection of the embryo and dispersal of seeds in the later stage. These events are required reproductive success of the plant and survival. There are changes in the hormone levels as well, which can trigger both seed dormancy and germination for the seed, based on the environmental cues. Post-fertilisation events are an important topic in the field of biology.
What are Post-Fertilisation Events?
The processes after fertilisation in plants, known as the post-fertilisation events, form the seeds and fruits. This includes division and later differentiation of the zygote into an embryo, followed by the formation of endosperm for nourishment and the process through which the ovule matures into a seed and the ovary matures into a fruit, thereby ascertaining propagation and survival of plant species.
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Formation of the Zygote
One of the sperm cells, from a pollen grain, fertilises an egg cell in the ovule to form a zygote. The zygote is diploid in nature and then undergoes division to form the embryo.
Definition and Formation
The fusion of the male and the female gamete becomes the key event in giving rise to a new plant and marks the initiation of seed development.
Structure and Development
After fertilisation, the zygote directly undergoes several mitotic cell divisions to form a multicellular structure, the embryo. The latter will differentiate to produce all the tissues and organs of the mature plant.
Endosperm Development
The endosperm is formed when the other sperm cell from the pollen grain fuses with the 2 polar nuclei, forming the triploid endosperm nucleus. The endosperm development is explained-
Types of Endosperm
The endosperm may develop in one of the following ways:
Nuclear endosperm: It is characterised by free nuclear divisions without immediate cell wall formation.
Cellular endosperm: In this type, the cell wall forms immediately after each nuclear division.
Helobial endosperm: It is intermediate between the free nuclear and cellular endosperm. In this, the primary division results in one large cell and one small cell.
Process of Endosperm Development
Soon after fertilisation, the endosperm develops and grows to form a store of nutrition that feeds the growing embryo. The endosperm undergoes successive cell divisions and differentiates to provide nutrition to the embryo.
Functions of Endosperm
The endosperm supplies the embryo with the required nutrients in the form of starch, proteins, and oils for its growth and development till the seedling becomes photosynthetic.
Embryo Development
The process of the formation of an embryo is called embryogeny. The stages of embryogenesis are:
Globular stage: It is when the embryo is a spherical mass of cells.
Heart-shaped stage: The differentiation of the embryo starts, and it begins to form the rudiments of cotyledons or the seed leaves.
Torpedo stage: Further differentiation occurs in the embryo to elongate it and form the fundamental structure of the plant.
Monocot vs. Dicot Embryo Development
Monocot and dicot embryo development differ mainly in the number of cotyledons—monocots have one, while dicots have two. These developmental differences influence seed structure and nutrient storage.
Embryogeny in dicots | |
The embryo has only one cotyledon. | The embryo has two cotyledons. |
The main parts are- cotyledon, the coleoptile (which covers the plumule), the coleorhiza (which covers the radicle), the plumule, and the radicle. | The different parts of the dicot seed embryo are- Radicle (future root), Plumule (future shoot), Cotyledons (two seed leaves that may store food), Hypocotyl (part between radicle and cotyledons), and Epicotyl (part above the cotyledons). |
Formation of Seed and Fruit
Seeds and Fruits are the products of sexual reproduction in flowering plants. The seed contains the embryo and stores food for the germination process, and the fruit is developed from the ovary and protects the seed.
The seed is the mature ovule, and the parts of a seed help in the protection and nourishment of the embryo.
The dicotyledonous seeds and monocotyledonous seeds have 2 cotyledons and one cotyledon, respectively. The cotyledons help in the storage of food and support the embryo.
The fruit is formed from the ovary after fertilisation. The fruit has a pericarp, and the seeds are contained inside the fruit.
There are mostly three kinds of fruits, which include simple fruits, aggregate fruits, and multiple fruits.
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Frequently Asked Questions (FAQs)
Seed dispersal enables plants to colonise new places; it reduces competition with plant parents and maintains species' existence and diversity as outcomes.
This will be determined by environmental factors like temperature, moisture, light, genetic makeup of the seed and the state dormancy.
Following fertilisation, related events to zygote formation, endosperm development, and seed maturation take place that forms fruits and seeds.
The endosperm with stored nutrients, formed during triple fusion, acts as a source of nutrition to the developing embryo for its growth and maturation into a seed.
In monocots, there is a single cotyledon present in the embryo called a monocotyledon, while that of dicots contains two. Therefore, the embryogenesis between these two are of different patterns.