What is Triple Fusion?- An Overview and Reproduction Structure of Angiosperms

The sexual reproduction of flowering plants results in the formation of fruits and seeds is known as Double fertilization. It takes place in both unisexual and bisexual plants with the help of male and female reproductive structures. Double fertilization involves the fusion of male gamete, egg cells and polar nucleus inside the ovaries of plant reproductive structure. It results in the formation of a zygote by syngamy and endosperm by triple fusion. Here, we are going to learn about triple fusion and its process in detail.

Keyterms: Sexual Reproduction, Flowering plants, Fruits, Seed, Double fertilization, unisexual plants, bisexual plants, male gamete, egg cells, polar nucleus, zygote, endosperm, triple fusion

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What is Triple Fusion?

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Triple Fusion is a process of sexual reproduction in flowering plants called angiosperms. In this, a fusion of one sperm nucleus with two polar nucleus takes place inside an embryo sac of an angiosperm which results in the formation of the endosperm. An endosperm is like a covering layer of an embryo and it contains oils, proteins that give nutrition in the form of starch.

Triple Fusion

Read More: Embryology

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Reproduction Structure of Angiosperms

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• A whole complete flower consists of four organs named sepals, petals, stamen and carpels which are attached to the stalk.
• Sepals are the first layer of flower that covers the flower bud and it is also known as the calyx.
• Next to the calyx, the petals are present which are coloured and it is also known as the corolla.
• The calyx and corolla are the non-reproductive part of the flower that are used to protect the inner parts and attract pollinators.
• The calyx and corolla constitute the perianth when both calyx and corolla are the same in colour and structure it is known as tepals.
• Next to the corolla, the stamens are present which is known as the male reproductive structure of angiosperms and it is known as androecium.
• Stamens produce spores and it usually has two parts, the filament and the pollen sac. The filament is the slender stalk that bears the pollen sac where the pollen is produced.
• Finally, at the center, the carpels are present which is known as gynoecium. It encloses the embryo sac and ovules with egg cells.
• The carpal is the combination of stigma, style, and ovaries where stigma and style are like a path between pollen sac and ovaries.
• After the fertilization process, the ovules result in the formation of seed, and carpels result in the formation of fruit.
   

Reproduction Structure of Angiosperms

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Triple Fusion Process

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• The stamen has another filament. When the anther contacts with stigma the pollen cells germinate and result in the formation of pollen tubes.
• The pollen tubes enter into the carpel of the flower and reach the embryo sac where it releases two male gametes(sperms nuclei).
• One of the male gametes fuse with the egg cell in the embryo sac and another male gamete fuses with two haploid polar nuclei located in the central cell.
• The fusion of male gamete with egg cells results in the formation of zygote and this fusion is known as syngamy.
• The fusion of one male gamete with two polar nuclei located in central cell results in the formation of triploid nuclei and this fusion is known as triple fusion.
• This fusion process results in the formation of endosperm which plays a significant role in the embryonic development.
• There are three types of endosperm development they are cellular, nuclear and helobial.

Read More: Biotic Factors

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Terms related to Triple Fusion

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Endosperm

The endosperm is a tissue that is a product of a fusion of male gamete and two polar nuclei cells and it is covering a layer of an embryo in a seed which acts as a food storage part and helps in embryonic development.

Endosperm

There are three types of endosperm formation, they are

• Cellular Endosperm Development
• Nuclear Endosperm Development
• Helobial Endosperm Development

Embryo

It is a part of seed covered by endosperm and it has premature roots, stems and leaves of a plant within it. It is formed as a result of fertilization in plants.

Double Fertilization

This is the process of fusion of one male gamete with the egg cell and another male gamete with the two polar nuclei results in the formation of zygote and endosperm respectively.

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Things to Remember

• There are two types of flowers in the plant kingdom, they are unisexual and bisexual. The reproduction of unisexual and bisexual flowers results in the formation of fruits and seed.
• The reproductive tissue of the plant is known as a flower which has four parts, sepals, petals, stamen, and carpel.
• Sepals and petals are like accessory parts of a flower that helps in the protection of reproductive parts and attracts pollinators.
• The stamen and carpel are the original reproductive structure in the flower.
• The unisexual flower has either stamen or carpel whereas the bisexual flower has both stamen and carpel in it.
• The stamen consists of anther and filaments whereas the carpel consists of stigma, style, and ovaries.
• The fusion of male gamete and female egg cells results in the formation of zygote whereas the fusion of male gamete with two polar nuclei results in the formation of endosperm.