Question

Как происходит двойное оплодотворение у цветковых растений

Answer 1

Уникальная особенность цветковых растений - двойное оплодотворение.

В завязь покрытосеменных растений проникает два спермия, один из них сливается с яйцеклеткой, дав начало диплоидному зародышу. Другой соединяется с центральной диплоидной клеткой. Образуется триплоидная клетка, из которой возникнет эндосперм - питательный материал для развивающегося зародыша. Этот процесс, характерный для всех покрытосеменных, открыт в конце прошлого века С.Г. Навашиным.

Answer 2

Double Fertilization in Flowering Plants

Double fertilization is a unique reproductive process that occurs in flowering plants (angiosperms). It involves the fusion of two sperm cells with two different female gametes, resulting in the formation of both a zygote and endosperm. This process is crucial for the successful development of seeds and fruits in flowering plants.

Process of Double Fertilization

The process of double fertilization can be divided into two main steps:

1. Pollen Tube Formation: Double fertilization begins when a pollen grain lands on the stigma of a flower. The pollen grain then germinates and develops a pollen tube, which grows down through the style towards the ovary. This process is known as pollen tube formation.

2. Double Fertilization: Once the pollen tube reaches the ovary, it enters the ovule through a small opening called the micropyle. Within the ovule, there are two female gametes: the egg cell and the central cell. The pollen tube releases two sperm cells into the ovule.

- Fertilization of the Egg Cell: One of the sperm cells fuses with the egg cell, resulting in the formation of a zygote. The zygote will develop into an embryo, which will eventually grow into a new plant.

- Fertilization of the Central Cell: The second sperm cell fuses with the central cell, which contains two polar nuclei. This fusion forms a triploid (3n) cell called the endosperm. The endosperm serves as a nutrient-rich tissue that nourishes the developing embryo.

Significance of Double Fertilization

Double fertilization is a unique feature of flowering plants and has several important functions:

1. Seed Development: The zygote formed through double fertilization develops into an embryo, which is protected within the seed. The seed contains all the necessary nutrients and structures for the embryo to grow into a new plant.

2. Endosperm Formation: The endosperm, formed through the fusion of the second sperm cell with the central cell, provides nourishment to the developing embryo. It is rich in nutrients such as starch, proteins, and lipids, which are essential for the growth and development of the embryo.

3. Fruit Development: After double fertilization, the ovary of the flower develops into a fruit. The fruit protects the seeds and aids in their dispersal. It also plays a role in attracting animals for seed dispersal through its color, scent, and taste.

Conclusion

In conclusion, double fertilization is a unique reproductive process in flowering plants. It involves the fusion of two sperm cells with two different female gametes, resulting in the formation of a zygote and endosperm. This process is essential for seed development, endosperm formation, and fruit development in flowering plants.