Welcome to our exploration of plant fertilisation. Fertilisation in plants is the fundamental process where male and female gametes unite to form a zygote. In flowering plants, this involves a remarkable mechanism called double fertilisation, which is unique to angiosperms. Let's examine the key structures involved in this process.
The fertilisation process begins with pollination, where pollen grains containing male gametes are transferred from the anther to the stigma. This can occur through wind, insects, or other pollinators. Once the pollen lands on a receptive stigma, it absorbs moisture and nutrients from the stigma surface. The pollen grain then germinates, forming a pollen tube that will grow down through the style toward the ovary.
Now we reach the remarkable process of double fertilisation, which is unique to flowering plants. The pollen tube enters the ovule through the micropyle and releases two male gametes into the embryo sac. The first male gamete fuses with the egg cell in a process called syngamy, forming a diploid zygote that will develop into the embryo. Simultaneously, the second male gamete fuses with the two polar nuclei in triple fusion, creating a triploid primary endosperm nucleus that will develop into the nutritive endosperm tissue.
Following fertilisation, remarkable developmental changes occur. The zygote undergoes repeated cell divisions to form the embryo, which will become the new plant. The primary endosperm nucleus develops into the endosperm, a nutritive tissue that provides food for the developing embryo. The entire ovule transforms into a seed, protected by a seed coat. Meanwhile, the ovary wall develops into the fruit, which protects the seeds and aids in their dispersal. This completes the reproductive cycle of flowering plants.
In conclusion, plant fertilisation is a sophisticated process that ensures the continuation of flowering plant species. It begins with pollination, followed by pollen germination and tube growth. The unique double fertilisation creates both the embryo and the nutritive endosperm. Finally, the development of seeds and fruits completes the reproductive cycle, allowing plants to disperse their offspring and maintain genetic diversity. This remarkable process has enabled flowering plants to become the most successful group in the plant kingdom.