Question

Почему эндосперм покрытосеменных растений триплоиден, а остальные клетки диплоидные?

Answer 1

Эндоспрерм - особая ткань, которая развивается после слияния диплоидной центральной клетки и гаплоидной гаметы. Все же остальные клетки и ткани есть результат митотического деления зародыша, образовавшегося после слияния мужской и женской гамет. (Все это происходит параллельно в завязи пестика и называется двойным оплодотворением).

Answer 2

Endosperm and Ploidy in Seed Plants

In seed plants, the endosperm is a tissue that provides nourishment to the developing embryo. It is typically triploid, meaning it contains three sets of chromosomes (3n), while the rest of the cells in seed plants are diploid, meaning they contain two sets of chromosomes (2n).

The ploidy level of cells is determined by the number of sets of chromosomes they possess. In most organisms, including plants, the ploidy level is determined by the process of fertilization. During fertilization in seed plants, the male gamete (sperm) fuses with the female gamete (egg) to form a zygote. The zygote then undergoes cell division to develop into an embryo.

In seed plants, there are two types of fertilization: double fertilization and triple fusion. Double fertilization occurs when one sperm fertilizes the egg to form the zygote, while the other sperm fuses with the central cell to form the endosperm. This process is unique to flowering plants (angiosperms) and is one of the reasons for their evolutionary success.

The endosperm is formed by the fusion of a haploid sperm cell with a diploid central cell, resulting in a triploid (3n) nucleus. This triploid nucleus then undergoes multiple rounds of cell division to form the endosperm tissue. The endosperm serves as a source of nutrients for the developing embryo, providing it with essential substances such as carbohydrates, proteins, and lipids.

On the other hand, the rest of the cells in seed plants, including the cells of the embryo, are diploid (2n). This means they have two sets of chromosomes, one inherited from the male parent (sperm) and the other from the female parent (egg). The diploid cells of the embryo will eventually develop into the various tissues and organs of the mature plant.

In summary, the endosperm of seed plants is triploid (3n) because it is formed by the fusion of a haploid sperm cell with a diploid central cell during double fertilization. The rest of the cells in seed plants, including the cells of the embryo, are diploid (2n).