Introduction

Seedless plants are those that do not produce seeds for reproduction. These plants have evolved a mechanism of reproduction known as "alternation of generations" where the diploid sporophyte generation produces haploid spores through meiosis. These spores then develop into haploid gametophytes, which produce both male and female gametes. One of the most notable characteristics of seedless plants is that their reproduction requires the presence of water for fertilization to occur.

Why is water needed for fertilization in seedless plants?

The answer to this question lies in the unique anatomy of the gametophytes in seedless plants. The male gametophyte (antheridia) produces sperm cells, which are released into the surrounding environment. The female gametophyte (archegonia) produces eggs, which remain encased in the plant tissue. For fertilization to occur, the sperm cells must swim through a film of water to reach the egg cell.

This is because the sperm cells do not have the ability to move on their own, as they lack flagella or other means of propulsion. Instead, they rely on water as a medium for transport. The sperm cells swim through the water until they reach the female gametophyte, which is usually located in a moist environment, such as near the soil surface or on the underside of leaves.

What happens during fertilization in seedless plants?

When the sperm cells reach the female gametophyte, they penetrate the tissue and fertilize the egg cell. This results in the formation of a diploid zygote, which develops into the sporophyte generation. The sporophyte grows out of the gametophyte, eventually becoming independent and producing its own spores through meiosis, thus completing the alternation of generations cycle.

It is important to note that the process of fertilization in seedless plants is entirely dependent on the presence of water. Without water, the sperm cells cannot reach the egg cell and fertilization cannot occur.

Conclusion

In conclusion, fertilization in seedless plants requires water because the sperm cells must swim through a film of water to reach the egg cell. This is due to the lack of locomotive structures in the sperm cells. The presence of water is therefore crucial for the continuation of the alternation of generations cycle in seedless plants. Understanding this process is important for the study of plant evolution and ecology.