Fertilization In Flowering Plants - SS3 Biology Lesson Note

Fertilization in flowering plants, also known as angiosperms, involves the fusion of male and female gametes, resulting in the formation of a zygote and the development of a seed. Here is an overview of the process of fertilization in flowering plants:

1.       Pollination: Pollination is the transfer of pollen from the male reproductive organs (anthers) to the female reproductive organs (stigma) of a flower. This can occur through various mechanisms, including wind, water, or the assistance of animals (insect pollination, bird pollination, etc.). Pollination is essential for bringing the pollen grains in contact with the stigma.

2.       Germination of Pollen Grain: Once the pollen grain lands on the stigma, it absorbs moisture and germinates. A pollen tube begins to grow out from the pollen grain, extending down through the style, a structure connecting the stigma and ovary.

3.       Pollen Tube Growth: The pollen tube grows through the style, guided by chemical signals and structures known as transmitting tissue. The pollen tube contains two haploid cells: the generative cell and the tube cell. The generative cell divides to form two sperm cells.

4.       Double Fertilization: When the pollen tube reaches the ovary, it enters the ovule through a small opening called the micropyle. At this point, double fertilization occurs. One sperm cell fuses with the egg cell, forming a diploid zygote, which will develop into an embryo. The other sperm cell fuses with two polar nuclei in the ovule's central cell, forming a triploid cell called the endosperm nucleus. The endosperm nucleus develops into the endosperm, which provides nutrients for the developing embryo.

5.       Seed Development: Following fertilization, the zygote and endosperm begin to develop within the ovule. The ovule matures and becomes a seed, which typically contains the embryo, endosperm, and a protective seed coat. The seed coat helps protect the developing embryo from desiccation and mechanical damage.

6.       Seed Dispersal: Once the seed is fully developed, it may be dispersed by various means, such as wind, water, animals, or self-dispersal mechanisms. Dispersal allows the seed to find new habitats for germination and growth.

Fertilization in flowering plants ensures the production of viable seeds, allowing for reproduction and the continuation of the plant species. The process of double fertilization, unique to angiosperms, ensures the formation of both the embryo and the endosperm, providing nutrients for the developing embryo. This successful fertilization and subsequent seed development contribute to the survival and dispersal of flowering plants in their environments.