Double Fertilisation: Definition, Process and Significance

Definition

Double fertilisation refers to the combination of two male gametes with one female gametophyte.

Double fertilisation, a major trait of flowering plant species, is their main characteristic. The phenomenon occurs when one female gamete is paired with two males. One of the male gametes fertilises an egg, which results in the formation of a zygote. Another unites with 2 nuclei polar for the formation an endosperm.

Double fertilisation stimulates the plant, leading to ovarian development to fruits as well as the development of ovules in the seed. The diploid state is achieved when the haploid female gametes and male gametes fuse.

Double Fertilisation in Angiosperms

Angiosperms are the most diverse and flower-bearing group of terrestrial plants. Angiosperms’ reproductive part is made up of flowers. They have separate male reproductive organs and female ones. Each one contains both sperm cells and egg cells.

Pollination is a way for pollen grains to achieve stigma through style. Two sperm cells enter the ovule synergid cell. This is followed by fertilization.

In angiosperms results in two structures: zygote & endosperm. Thus, the term “double fertilisation”

Double fertilization (also known as double fertilisation) is a complicated process in which two sperm cellular fusions occur. One fuses to the egg cell, the other with two polar nuclei. These fusions produce a diploid (2n), and a triploid (3n), the primary embryo sperm nucleus.

Endosperm is created by the fusion of three haploid nuclei. This is known as triple fusion. The primary endosperm nuclear unit eventually becomes the primary endosperm cell, then the endosperm.

After numerous cell divisions, the embryo is formed from the zygote.

Angiosperms develop an embryo

Once fertilisation is complete, embryonic development begins. No more sperms are allowed into the ovary. The fertilised ovule becomes a seed. Ovarian tissues form a fleshy egg that surrounds the seed.

After fertilisation, the embryo divides into the lower terminal cell and the lower basal cells. The basal cells develop into suspensors, which help in the transportation of nutrients to the developing embryo. The terminal cells develop into pro-embryo.

The following are the stages involved in developing an embryo.

Angiosperms Embryonic Development: Stages

1. The terminal cell divides and forms a globular proembryo in the first stage. The basal cell divides into a suspensor.
2. Due to the presence of cotyledons, a developing embryo achieves a heart-shaped shape.
3. The growing embryo becomes crowded and begins bending.
4. The embryo completes the seed.

Significance of double fertilisation

This is the significance of double fertilisation:

1. Due to double fertilisation, two products can be obtained.
2. Polyembryony can occur, and the plant is more likely to survive.
3. Double fertilisation results in an endosperm which provides nourishment for the embryo.
4. It increases the viability and quality of the angiosperm seeds.
5. It makes use of both male gametes that are produced by pollen grains.