Technology of storage and primary processing of agricultural products

Questions for self-examination
1. What is the origin and significance of the doctrine of the biosphere?
2. What are the main geological strata and the distribution of life in them?
3. What is the importance of studying biomass?

5 LABORATORY WORK.

Topic: The growth of the dust tube. Double fertilization

The purpose of the work. Gain an understanding of the process of fertilization in plants, sporogenesis and gametogenesis. It consists of studying the process of merging gametes formed in the dust with gametes formed in the apical sac.
The content of the work. In plants, sex cells forming process will take place in two stages: the first stage sporogenezda gaploid chromosome cells - and will be playing in the second stage - gametogenezda a few times as a result of the division gaploid chromosome cells to the oocyte is formed.
Clove powder plants, microspores forming process mikrosporogenez, female sex cell - Megasport forming process called megasporogenez.
In the subepidermis tissue of the young pollen, a special spore-forming tissue - archespores - is formed. Archespora divides by meiosis and forms four haploid chromosomal microspores - tetrads, which are attached to each other .
As a result of the maturation of the microspores , the cell tetrad separates from each other, forming dust particles wrapped in two separate shells . The outer shell exina surface is rough with holes, the inner shell intina surface is smooth. At the same time, the process of microsporogenesis ends and microgametogenesis begins.

Figure 1
As a result of the first mitotic division of the microspore nucleus, a number of large vegetative and small generative cells are formed. In the latter - the second mitotic division, the generative cell divides to form two male cells - sperm. The vegetative cell and its nucleus do not divide; in which the reserve nutrients accumulate, allowing the generative cell to divide and the pollen tube to grow along the seed column .
This means that a spore with a haploid number of chromosomes splits twice by mitosis , resulting in the formation of 3 cells in the dust sac - two sperm and one vegetative cell.
An archespore cell is formed in the subepidermal layer (apical sac) of the young seed bud located in the flower node . It divides by meiosis , forming four megaspores on the haploid chromosome. One in four cells grows; and three perish and are gradually absorbed into the cytoplasm. This phenomenon is called megasporogenesis.
Then the process of megagametogenesis begins. In this case , a single growing cell of the tetrad, the nucleus of the megaspore , divides 3 times by mitosis , but the cell does not divide. As a result of this division , eight nuclei of the same size are formed. When four of these nuclei are located in the aunt part of the sperm and the other four in the micropile part , they become independent cells . Then one cell from each pole moves towards the center of the apical sac. The remaining three cells in the micropile part of the ovary are called the egg apparatus, the large cell in the middle is called the egg cell, and the satellite cells on either side of it are called synergists . The two cells with the haploid chromosome located in the center of the atrial sac are called the central cells of the atrial sac, and they often do not join each other until they are fertilized. The three cells located in the aortic portion of the apical sac are called antipodes.
Thus, as a result of three consecutive mitotic divisions of the megaspora in the ovarian sac , eight nuclei of the same genetically identical, haploid chromosome are formed, of which only one matures and becomes an egg cell.
The mature pollen grains of the plant begin to germinate slowly as they fall into the maternal beak of the flower . Some plants , each in the dust of them 2 Some of the sperm nucleus (cotton and tobacco), 3 nuclear plants (g'alladosh). It is known that as a result of the division of the generative cell , a sperm nucleus is formed inside the dust grain . This process occurs during the growth of the dust tube.
For example, in a cotton plant, the maturation of 2 sperm nuclei occurs 8-9 hours after pollination in a pollen tube. The growth of the pollen tube is due to the bulging growth of the spore intina shell .
In some plants, for example in the G.hirsutum type of cotton , several (2-3) pollen tubes germinate from one pollen grain . Vacuum tube motherhood tumshuqchasining later motherhood column pass through the tissue to grow seeds in the bud . In the cotton plant, the maximum growth rate of G hirsutum powder tube is 1.6 mm per hour, passing through the maternal column is 10-13 hours. The number of growing dust depends on the number and quality of dust particles that fall into the mother’s beak. Usually there are a large number of pollen tubes growing into the uterine column , but very few of them reach the ovary and the ovary sac. The muzzle bag can sometimes hold one, and sometimes even 2-3 dust tubes. It was observed that the number of seed buds that reach 2-3 pollen tubes in a cotton plant is 5-6% .
The pollen tube is responsible for delivering sperm into the ovarian sac . After the sperm nucleus maternal reproductive cell (tuxumxujayra added).