Mesogamy

Plants live up to their moniker of “primary” or “universal” producers. They are truly a gift from nature, providing us with necessities like clothing, shelter, food, and oxygen. Plants, like all other living creatures, breathe, vegetate, germinate, excrete, and produce. Ralph B. Strassburger was the first to identify the fertilisation mechanism in blooming plants in 1884. Let’s take a closer look at the fertilisation process in plants.

What is the definition of fertilisation?

Fertilization is the process by which plants reproduce sexually as a result of pollination and germination. After carpal pollination, male gametes (pollen) unite with female gametes (ovum) to generate diploid zygote in a physicochemical process. The entire process takes place within the zygote, which then develops into a seed. Male gametes are delivered into female reproductive organs by pollinators during the procedure (butterflies, birds, honey bees, bats, and flower beetles). As a result, an embryo develops in a seed. Flowers are the reproductive organs of angiosperms, and they reproduce in a different way than the rest of the plant.

• Pollination occurs when pollen-coated male gametes are moved away by water, wind, or other agents like animals and insects. The pollen is then directed to land on the plant’s stigma. Pollination is the term for this process.

• Germination is the process through which the pollen tube grows and penetrates the egg cell in a number of minutes. The pollen grain travels through the tube to reach the egg.

• Ovule Penetration: The pollen tube containing the sperm penetrates the embryo sac, also known as the ovule.

• Fertilisation: The sperms travel down the tube to fertilise the egg after successfully piercing the ovule. The polar nuclei and egg in the ovule are fertilised in most flower-bearing plants, resulting in twofold fertilisation.

The zygote cells divide and develop into an embryo, which is also known as a developing plant, after fertilisation. The embryo was encased in a seed capsule and remained dormant until favourable environmental conditions allowed it to mature into a plant.

Seed Plant Fertilisation

Seeds grow on both sides of leaves or scales, create cones, or predominate at the end of short stalks during the fertilisation process in gymnosperms or seed-bearing plants. The seed is kept inside the ovary.

Flower-bearing Plant Fertilisation

A second fertilisation mechanism happens in the central cell of flower-bearing plants called angiosperms. Either one of the pollen grains releases two sperm cells. For egg fertilisation, the first cell fuses with the zygote, while the second fuses with the twin polar nuclei to generate endosperm.

Fertilisation Process

Fertilisation occurs as a result of the fusing of female and male gametes, as previously stated. Both female and male pollen grains must reach the stigma’s surface for fusion to occur. Pollination is the term for this process. The pollen is delivered to the stigma and germination occurs, with the pollen travelling through the style and into the ovule. Pollen or microspores have two types of cells: generative and pollen tube cells. This pollen tube cell creates a pollen tube for generative cells to travel through.

Pollen tubes require oxygen, water, and various other chemical signals to germinate. While pollen flows through the style on its way to the ovule or embryo sac, the style’s tissue supports the pollen tube’s growth. If the generative cell has not yet ruptured into two cells, it breaks down into two sperm cells during the entire process. Pollen is helped in penetrating the ovule through the micropyle by the chemical production of synergids in the embryo sac.

A diploid zygote is formed when one sperm cell from the sperm cells germinates in the egg cell. The polar nuclei of the surviving sperm cells fuse to form a triploid cell, which produces endosperm. Double fertilisation refers to the twin fertilisation episodes that occur in angiosperms or flowering plants. It is impossible for another sperm to enter after the fertilisation process is completed. The seed is produced by the fertilised embryo sac, while the ovary’s tissues form the fruit that envelops the seed.

Self-Fertilisation

Allogamy is the process by which gametes from two different species – male and female – cross-fertilize. When two gametes from a single individual fuse, this is known as autogamy or self-fertilisation. Hermaphrodites, such as plants and flatworms, are examples of this.

Fertilisation Types

There are three different methods of fertilisation, based on how pollen tubes penetrate the ovule or embryo sac.

Porogamy

Flowering plants, often known as angiosperms, are the most prevalent source of fertilisation. A pollen tube reaches the ovule through a micropyle in this shape. Lilies are a common example.

Chalazogamy

This type of fertilisation occurs in the casuarina plant species. Rather than entering through the micropyle, the pollen tube enters the ovule through chalaza. This is a rare occurrence. Casuarina, Betula, and Juglans are some examples.

Mesogamy

Cucurbit plants, such as bitter gourd, ridge gourd, and numerous other gourd plants, as well as pumpkin, are fertilised in this way. In this form, a pollen tube penetrates the ovule by passing through integuments or its centre portion.

Double Fertilisation

When a single female gamete fuses with two male gametes, this is known as double fertilisation. One of the sperm cells fuses with the zygote, while the other fuses with the two nuclei, resulting in endosperm. The entire angiosperm plant goes through a double fertilisation procedure.

Conclusion

• When you fertilise twice, you get two products.
• Increases the viability of the angiosperm seeds.
• Polyembryony will increase the plant’s chances of survival (the chance to form more than a single embryo from one seed or a single fertile ovum)
• The endosperm produced by double fertilisation feeds the growing embryo.
• The two male gametes produced by pollen grains are put to good use.

These are the various methods of fertilisation in plants, as well as the processes involved. To Understand the differences between various types of fertilisation, you must first understand the notion of fertilisation.