Each living organism goes through a certain life cycle: from conception (laying) to death (death), and plants are no exception. Their distinctive feature is the process of reproduction, which consists in the alternation of sporophyte and gametophyte.
But what is a gametophyte - in more detail we will analyze in this article. It should be said that quite often the gametophyte is not isolated, but exists in conjunction with the sporophyte or directly depends on it.
What is a gametophyte?
The term "gametophyte" comes from the Greek word "gamete", that is, the reproductive cell and phyton (plant) and in translation means the sexual generation or one of the stages of plant development. In biology, the haploid sexual generation has a letter designation - "n".
Kinds
To understand what a gametophyte is, you need to understand how it is formed and what it is. Gametophyte is a hallmark that characterizes the plants belonging to the class of Higher spore. Depending on the differentiation in gametophyte, gametangia (generative organs of sexual reproduction) of two types may develop: female and male.
Propagation Features
The entire process of sexual reproduction in plants occurs in the form of conjugation (i.e., the fusion of protoplasts of two independent vegetative cells). Often on the same individual both gametes and spores can develop simultaneously. But there are also cases in which disputes develop only in one form, and gametes exclusively in another. The individual on which spores develop is called sporophyte, and the one on which gametes are formed is called gametophyte.
Gametophyte in plants
Gametophyte is bisexual and same-sex. In sporophyte, the nuclei have a diploid chromosome set, but in the gametophyte, they are haploid. The vast majority of highly organized algae and almost all higher plants have a clear pattern in the cyclic development and alternation of generations that are reproduced asexually and sexually.
Schematically, the reproduction process can be represented as follows: gametophyte → gamete production → gamete fusion → zygote formation → development of diploid sporophyte → and so on.
The structure of the gametophyte is quite diverse and this directly depends on the types of generational change in certain plant species. So, for example, algae have a uniform generational change (isomorphic), therefore the gametophyte in them is represented by an independent unit that exists separately and is no different from the same sporophyte.
But for laminaria algae, which have a distinctive (heteromorphic) development cycle, the gametophyte has a completely different structure, different from sporophyte, in the form of underdeveloped filamentous and branched thalli. In almost all representatives of sporophytes, including fern-shaped, gametophyte is completely underdeveloped and there is a very short time.
Due to the fact that during the evolution of plants of higher classes a smooth reduction of gametophyte was observed, they lost their gender. For example, seed plants have completely lost the female generation, and all stages of development in them occur on the sporophyte.
Female gametophyte of gymnosperms is represented by multicellular haploid endospermia or several archegonia, as in pine or other gymnosperms, respectively. In equidistant representatives of fern-shaped plants, the sprouts have both sexes.
Male gametophyte of seed plants has the appearance of pollen and originates from microspores, which form gametes, growing into a pollen tube. But the overgrown fern-like growths are bisexual.
Thus, gametophyte does not depend on the timing of the growing season or plant life, but only on its species and evolutionary features.
Conclusion
Thus, the gametophyte, as a sexual generation in the development of plants and characterized by a certain and consistent alternation of generations within its species, has several features. First of all, it is formed from spores, has a haploid set of chromosomes and always forms gametes, regardless of whether they are specialized genital organs or ordinary vegetative cells.
Now you know what a gametophyte is and what its features are.