Topic: “Why is flowering plants called fertilization double” is studied in the sixth grade of the school. However, not every adult can explain the subtleties of this process.
Plants, like all living things, reproduce using three main methods. The first is vegetative, that is, a new plant appears from any part of its "parent" - the root, stem, leaf, even a single cell. The second is called asexual, because plants emerge from spores and are similar to mothers. So mushrooms and some algae multiply. The most perfect is the fertilization of plants sexually.
In the plant world, this process occurs through the fusion of gametes, which can be the same in size (isogamy), different in size (heterogamy) and fundamentally different from each other (oogamy). We can say that fertilization is the process of combining male (sperm) and female (egg) gametes, which results in the formation of a cell with a double set of chromosomes (zygote), from which a new plant will emerge.
Why is flowering called double fertilization? There is a special organ of reproduction - a flower. Its constituent parts are: stamens on a duster with anther (contains pollen), ovary, column, pestle (with stigma), pollen tube, which reaches the embryo sac, where the ovule is located. From the course of school biology, many remember something about the pestle and stamen and may think: this is why in flowering plants fertilization is called double. But this is not so.
In the anther, as already mentioned, pollen is formed, which consists of two cells - a large vegetative and a smaller, generative one. When the anther opens, these elements are spread by wind or insects. Once on the pestle (directly on the stigma), the pollen cells sprout so that the vegetative part becomes a pollen tube attached to the embryo sac. Through it, a generative cell enters the bag, which during its penetration is divided into two sperm. One of them reaches the egg, merges with it, forming a zygote, and the second connects to the secondary nucleus. This process is the reason why in flowering plants, fertilization is called double.
Some modern plants successfully combine different methods of reproduction, which increases the survival of the species. And at the time when this process was just beginning, this method of reproduction was a very important, evolutionary process. This is due to the fact that an organism created by fusion of cells with different sets of chromosomes had greater variability and adaptability to the environment. Modern physical and chemical studies have shown how sexual reproduction of plants is complex in nature. For example, it was found that pollen and stigma of the pestle have different pH levels, different levels of the isoelectric point of proteins, different enzyme and amino acid composition, which, however, contributes to the optimal course of physiological processes when these cells combine.
