In this article we will consider biological concepts that relate to the vital activity of higher plants. This gametophyte and sporophyte, which are components of the life cycle of these amazing organisms.
Features of higher spore plants
Higher spore plants are the first terrestrial organisms of this Kingdom of living nature. The first descendants to the land, called rhinophytes, had a stalking, fork-branching stem. Some fossil representatives of this systematic unit were giant in size, reaching a height of several meters. To master the land-air environment to these plants allowed a number of progressive signs that appeared in their evolutionary process. First of all, they are mechanical and conductive tissues. Thanks to this, new life features have become possible. This is the vertical position of their body in space and the conduct of nutrients throughout the body. Among modern plants representatives of this systematic unit are 4 departments. These are mosses, plauna, horsetail and fern-like. The gametophyte and sporophyte are two generations of a single plant that consistently alternate during their life cycle. This process ensures the continuity of species existence.
Features of sporophyte
Sporophyte is a sexless generation of spore plants. Consider its structure using the example of bryophytes. In summer, on the green shoots of this plant, small boxes appear on elongated legs. Inside them there are spores - cells of asexual reproduction. Getting into the soil, they give rise to green shoots, which already reproduce with gametes. Sporophyte prevails in spore plants, horsetails and ferns, as well as in all seed plants. The gametophyte is dominant only in all bryophytes, which has the appearance of a green leafy shoot.
Cells of asexual reproduction develop in specialized organs, which are called sporangia. In mosses this is a box on the stem, in the case of the paportniki there are Soruses located on the underside of their leaves. A horsetail and a plauna form pineal formations on the tips of spring shoots, which are called Sorus.
Sporophyte horsetail is represented by shoots of two kinds. In spring a sporiferous stalk of brown color appears. There is no chlorophyll in his cells. It develops before the germination of the spores, and then dies. Of the kidneys located on the rhizome, a green summer shoots grow. It is chlorophylliferous. This structure is clearly separated by interstitial sites with reduced leaves. The gametophyte of this plant is practically invisible. This plate is only 1 cm in size. Some of them develop female gametes, on others they are male gametes. Therefore, the sexual generation of horsetails is dioecious.
Plaunas are also characterized by a predominance of sporophyte in the life cycle. These are herbaceous plants with whole leaves. They grow round, therefore people deserve the name "witch rings". Perennial shoots spread along the ground and have raised stems. Their spores, collected in strobila, are in the ground for several years, after which they germinate.
What is gametophyte
The gametophyte and sporophyte are generations, successively replacing each other. When spores germinate, they give rise to the sex generation. It is called a gametophyte. In mosses, both generations are anatomically related, and in the remaining spores develop separately. For example, in ferns the gametophyte has the appearance of a flat plate on which a bundle of accessory roots develops. As a result of its development, the fern gametophyte, which is also called a sprout, gives rise to the asexual generation.
The concept of the life cycle
Sporophyte plants give rise to the sex generation. Sex cells are formed on the gametophyte, for the fusion of which a necessary condition is the presence of water. Therefore, all spore live on well-moistened sections of land. The gametes, in contrast to the spores, have a single set of chromosomes. It is restored as a result of fertilization, therefore the gametophyte itself is always diploid.
So, the sporophyte is a generation of plants with the help of which their asexual reproduction is carried out. In the course of the life cycle, it is replaced by the genital generation - the gametophyte.