Flowering plants are distinguished by the fact that they fertilise themselves twice. In this phenomenon, one female gamete fuses with two male gametes to form a new gamete. The formation of a zygote occurs when one of the male gametes fertilises an egg, and the construction of an endosperm occurs when the other male gamete joins with two polar nuclei to form an endosperm.

Double fertilisation stimulates the growth of the plant, culminating in the development of ovules into fruits and the development of ovarian development into the seed. It is only after the haploid male gametes and female gametes unite that the plant is restored to its diploid state. The suspensor is formed as a result of the division of the basal cell, which finally connects with the maternal tissue.

Double Fertilization in Angiosperms

Angiosperms are flower-bearing flora, and they are the most diverse institutions of terrestrial plant life in terms of structure and function. The reproductive component of angiosperms is shaped by the flowers, which contain separate male and female reproductive organs. The gametes carried by each of them are sperm and egg cells, respectively.

Pollination aids in the transportation of pollen grains to the stigma by style. The two sperm cells make their way into the ovule-synergid cell. This is followed by the process of fertilisation.

Fertilization results in the formation of two structures, specifically the zygote and the endosperm, which gives rise to the term “double fertilisation.”

Doubling the number of sperm cells results in two polar nuclei, one of which fuses with the egg mobile and the other which fuses with the other two polar nuclei, resulting in two diploid (2n) zygotes and a triploid (3n) number one endosperm nucleus (PEN), respectively.

Triple fusion is the term used to describe the process by which endosperm is created by fusing three haploid nuclei together. Endosperm nuclei grow into the number one endosperm mobile (p.c.) and then into the endosperm in their final stages of development.

After a number of cell divisions, the zygote will develop into an embryo.

The embryo begins to develop, becomes congested, and eventually begins to bow.

During the last stage, the embryo entirely fills the seed’s volume.

Development of Embryo in Angiosperms

The instant the process of fertilisation is completed, the embryonic development process is initiated, and no further sperm cells are permitted to pass through the ovary. The fertilised ovule develops into a seed, and the ovarian tissues mature into a fleshy fruit that surrounds and protects the seed during development. Following the fertilisation process, the zygote divides into two cells: the higher end cell and the lower basal cell. When this happens, the suspensor transforms into a device that helps to transfer nourishment to the developing embryo. The higher terminal cell develops into a pro-embryo during development.

Phases of Development of Embryo in Angiosperms

The following are the stages of an embryo’s development that occur at various times throughout its life:

• The terminal cell dissociates during the earliest period of development, resulting in the formation of a globe-shaped pro-embryo. As an added bonus, the basal cell divides and becomes a suspensor.
• Because of the presence of cotyledons, the growing embryo takes on a heart-shaped form as it develops.
• During development, the developing embryo becomes crowded and begins to adjust into various shapes.
• The embryo takes up the entirety of the seed’s surface area.

Significance of Double Fertilization

• Due to the fact that there are only two fusions, only two products are produced.
• The triploid primary endosperm nucleus (PEN), which is produced as a secondary product of fertilisation, develops into a nutritive tissue known as the endosperm, which is responsible for giving nutrition to the developing embryo.
• The outcome of the fusion process retains the diploid state that existed earlier in the life cycle. The diploid zygote develops into an embryo, which then develops into a new plant as a result of the process.
• The process of double fertilisation entails the use of both the male gametes produced by a pollen grain and the female gametes.
• As a result, the likelihood of poly-embryology increases, which in turn improves the likelihood of the new plant surviving and reproducing.
• Double fertilisation stimulates the growth of the plants’ reproductive organs, which are responsible for the development of ovary into fruits and ovules into seeds.
• Due to the fact that angiosperms are characterised by double fertilisation, the seeds of angiosperms are extremely accessible.
• A result of double fertilisation is the re-fusion of characteristics, which results in variance in the qualities of the offspring.

Conclusion

Plants that blossom have a sophisticated fertilisation technique that is called double fertilisation . In this procedure, a female gametophyte (megagametophyte, also known as the embryo sac) is joined together with two male gametes (sperm). It is important to note that in angiosperms, double fertilisation results in the production of an embryo as well as an endosperm, both of which are necessary for the generation of viable seed. Diploid plants produce diploid embryos and triploid endosperm tissue, while triploid plants produce triploid endosperm tissue. There are two maternal parent genomes in the endosperm, and one paternal parent genome in the endosperm .