Double Fertilisation in Plants

Double fertilisation is a unique reproductive process that occurs in angiosperms (flowering plants). It involves the fusion of two male gametes with two female gametes, resulting in the formation of both a zygote and endosperm. This process is essential for the successful development of seeds and plays a crucial role in plant reproduction and survival.

Male and Female Gametophytes
- In plants, the male gametophyte is the pollen grain, which contains two sperm cells.
- The female gametophyte, also known as the embryo sac, is located within the ovule of the flower. The embryo sac consists of seven cells, including the egg cell and two polar nuclei.

Pollination
- Before double fertilisation can occur, pollination must take place. Pollination is the transfer of pollen from the anther (male reproductive structure) to the stigma (female reproductive structure) of a flower.
- Pollen grains are carried by wind, water, or animals, such as bees or birds, to the stigma.

Double Fertilisation Process
1. Pollen Germination:
- Once the pollen grain reaches the stigma, it germinates and produces a pollen tube.
- The pollen tube grows down through the stigma and style, eventually reaching the ovary where the ovules are located.

2. Two Male Gametes:
- The pollen tube releases two male gametes into the embryo sac.
- One male gamete fertilises the egg cell, resulting in the formation of a zygote, which will develop into an embryo.
- The other male gamete fuses with the two polar nuclei to form a triploid nucleus.

3. Formation of Endosperm:
- The fusion of the second male gamete with the polar nuclei results in the formation of a triploid nucleus, which is called the primary endosperm nucleus.
- The primary endosperm nucleus divides repeatedly by mitosis, forming the endosperm.
- The endosperm serves as a nutrient-rich tissue that nourishes the developing embryo.

4. Seed Development:
- The zygote develops into an embryo, which consists of a radicle (embryonic root), a plumule (embryonic shoot), and one or two cotyledons.
- The endosperm and embryo together form the seed.
- The seed matures within the ovule and is eventually dispersed to new locations for germination and the growth of a new plant.

Significance of Double Fertilisation
- Double fertilisation ensures the coordinated development of the embryo and endosperm, providing the necessary nutrients for the embryo's growth.
- The endosperm acts as a food reserve, supplying nutrients to the developing embryo until it can establish its own photosynthetic capabilities.
- This process increases the efficiency of nutrient utilization and enhances the survival and success of angiosperms in various habitats.
- Double fertilisation is a key characteristic that distinguishes angiosperms from other plant taxa and contributes to their evolutionary success.

Double fertilisation in plants is the process in which the fusion of one male gamete with egg cell and also the fusion of second male gamete with central cell in the embryosac of a flower this processes take place simultaneously and this whole process is called double fertilisation in plants .
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