Plant cell division and plant meristematic tissue experiments
Plant cell division and plant meristematic tissue experiments
Source of content: Microbiology Lab.
Operation method
Plant cell division and plant meristematic tissue experiments
Principle
1. to understand the three modes of plant cell division; to recognize the location of meristematic tissues on the plant body and their types. 2. to understand the characteristics of the phases of mitosis and meiosis in plant cells; and to understand the structural features of meristematic tissues.
Materials and Instruments
Onion Root Tip Duckweed Garlic Seedling Permanent Flake Rape Stem Tip Fresh Stem Walnut Acacia Branches Wheat Young Stem Move I. Plant Cell Division For more product details, please visit Aladdin Scientific website.
Glacial acetic acid Acetic acid Magenta acetate GV Acetic acid Potassium iodide Senna water
Microscope Water cups Scissors Petri dishes Beakers Finger tubes Droppers Slides Coverslips Absorbent paper Alcohol lamps Blades Tweezers Dissecting needles Yarns Brushes
Plant cells are constantly undergoing cell division to increase the number of cells as they undergo growth and development. There are three types of plant cell division: mitosis, amitosis and meiosis, of which the most common and widespread is mitosis.
1. Observation of mitosis in plants
(1) Mitosis is the most common form of cell division in eukaryotic cells.
It is named mitosis, also called indirect division, because of the presence of chromosomes and spindle filaments during cell division.
The process of mitosis is complex and includes two steps, nuclear division and cytoplasmic division. People usually divide nuclear division into interphase, prophase, metaphase, metaphase, metaphase and metaphase for the convenience of explanation. But in fact, nuclear division is a continuous process, there are a series of transition states in the middle of each period, which should be carefully observed and understood in the course of the experiment.
(2) Place the onion in a cup of water with the water just touching the base of the bulb disk of the onion, and the onion will grow white roots in 3-4 days. The roots can be cut and used when they reach a length of 1-1.5 cm.
The material can be fixed by placing the cut root tips in glacial acetic acid-alcohol fixative for 2-24 hours at room temperature. If the fixed material is not used in time, it can go through 50% alcohol to 70% alcohol for half an hour each, and then change to 70% alcohol to keep it for spare.
The fixed material is placed in a dissociative solution of alcohol and concentrated hydrochloric acid for 10-20 minutes to dissociate the intercellular layer of the root tip. If fresh material is used, the material can be taken and placed directly in the dissociation solution, which can simultaneously play the role of fixation and dissociation. The length of dissociation time depends on the material, onion or wheat dissociation time can be slightly longer, broad bean dissociation time can be slightly shorter. However, it should be noted that the dissociation time of various materials should not be too long, otherwise it is not easy to stain.
After dissociation and then change the alcohol a glacial acetic acid fixative for 5-10 minutes, can play a role in the softening of the cell wall (i.e., re-erosion of the cell wall).
Then wash off the fixative, place the material in a finger-shaped tube or a small beaker of water for 4-5 times, wash the hydrochloric acid, conducive to staining.
Place the material on a slide, cut off the extension zone and the root crown part, leaving the apical part of the meristematic part of the root tip about 1 mm, add 1 drop of acetate magenta staining solution, leave for 10 minutes, until the root tip is stained to a dark red color, add a coverslip, place the blotting paper or gauze on the top of the coverslip, the left hand presses down on the slide, and with the right hand thumb on the blotting paper or gauze, applying pressure on the apical part of the root tip, pressing the apical material into a homogeneous thin layer. The pressure should be appropriate so that the cells and chromosomes can be spread out; excessive force may destroy the chromosomes. To increase the staining effect, the carrier sheet can be slightly heated on an alcohol lamp.
Finally, a drop of water can be placed on one side of the coverslip, and the water can be sucked into the coverslip from the opposite side of the coverslip with absorbent paper for microscopic observation. By moving the slide around and checking it during the observation, the various stages of mitosis can be found in different fields of view.
This experiment can also be used 1% gentian violet staining for 1 minute, with 20% acetic acid (50% alcohol preparation) wash for a few seconds after the preparation of observation, the chromosomes can be seen as blue-purple.
2. Observation of plant cell mitosis
There are various forms of mitosis, the most common is the transverse constriction division, the cell nucleus is first elongated, then constricted in the middle and finally broken into two daughter cell nuclei. Observe the epidermis of the leaf sheaths of metatarsal or garlic seedlings under a demonstration microscope to understand the phenomenon of plant cell mitosis.
3. Observation of meiosis in plant cells Meiosis is the cell division that occurs when plants undergo sexual reproduction. The process of cell division is similar to that of mitosis, but the cell divides twice in a row, and the chromosomes are replicated only once, so a mother cell divides into four daughter cells, and the chromosome number of the daughter cells is only half of the chromosome number of the mother cell.
Observe the permanent mounts of plant cells in meiosis during the dichotomous and tetramerous periods to understand the phenomenon of plant cell meiosis.
Plant meristematic tissue
The meristematic tissues are composed of cells with vigorous dividing functions and are found in the young growing parts of the plant body. According to its position in the plant body can be divided into three types: apical meristem, lateral meristem and intermediate meristem.
1. Observation of apical meristem
A 2 mm long section of onion root tip was cut, and the cut tip was cut in half along the longitudinal axis from the center, placed in a 1:1 mixture of concentrated hydrochloric acid and alcohol (95%) for 5 minutes to kill, fix and dissociate the material.
After dissociation, the material was rinsed with water for 10 minutes (just swish the material in water a few times), then the root tip was placed on a slide with a drop of magenta acetate (or iodine solution), and the tip cells were gently dispersed with a knife, and the nuclei were colored after 20 minutes, and the excess dye was removed by aspiration, and the slides were prepared with a drop of water.
First placed under low magnification observation, you can see the apex of the root tip of a cap-like structure, is composed of many loosely arranged cells, called the root crown. Inside the crown is the apical meristem of the root tip. Inside the root crown is the apical meristem of the root tip.
When the lens is converted to high magnification, it can be observed that the cells are tightly arranged, no pores exist, and the shape of the cells is almost equal in diameter. The cell walls are thin, the cytoplasm is dense, and the vesicles are small. The nucleus is larger in proportion to the cell, resides in the center of the cell, and has the ability to divide constantly. Due to the constant division of this part of the cell, the apical growth of the root tip is caused. If the longitudinal section of the stem tip of oilseed rape or other plants to observe, in addition to the periphery of the stem tip without a root crown type of organization and replaced by the leaf primordium and young leaves, the morphology of the apical meristem is also similar to the characteristics.
2. Lateral phloem
Take broad bean or alfalfa fresh stem section, make a freehand transverse section (stained with 1% saffron solution, or made into saffron - fast green double staining of the permanent slide specimen), placed under the microscope observation, you can see the arrangement of vascular bundles arranged in a ring, in the vascular bundles between the xylem (in the section, near the center of the stem, the part of the part of the red saffron stained red) and the phloem (and the xylem at the opposite end, such as the fast green staining, it is stained green or dark green). (the end opposite the xylem, stained green or dark green if stained with fast green), several layers of flattened cells can be clearly seen. The layer of flat cells, also more closely arranged, this is the formation of the layer of cells. The result of cell division can make the stem thicker, so it is called lateral meristematic tissue. Such as plants with secondary growth.
(1) Roots as material, the same can be seen in a similar situation, and make the roots thicker.
In order to more carefully observed to the characteristics of the formation of layer cells, can take walnut, acacia branches, will be stripped of its bark, with a razor blade or forceps in the bark or woody stem of the fresh wound on the surface of the tear or cut a very thin layer, for temporary section, placed under the microscope, you can see the formation of layer cells longitudinal morphology, there are two kinds of, one for the spindle-shaped primitive cells, the other is almost equal to the diameter of the ray of the primitive cells. Spindle-shaped primitive cells, its length than the width can be several times or many times larger, while the cell has a clear intracellular vesicles.
(2) take acacia or other species of old branches, for freehand transverse sections, with 1% aqueous solution of fenghuang temporary sealing microscopic examination, can be observed in the edge of the stem section also has several layers of flat cells, arranged neatly and closely, is the secondary protective tissue - pericarp, which stained red, cells without inclusions of dead cells, for the cork layer. Inside the cork layer there is a layer of light-colored and flat cells for the cork-forming layer, is another kind of lateral meristematic tissue. Its cell division activity results in the formation of the cork layer and the inner layer of the cork, forming the periderm.
3. Interstitial phloem
Take young stems of corn or wheat and make freehand longitudinal sections for temporary sealing and observation or take permanent sections that have been made and observe them under the microscope. Note that at the base of the internode there are some smaller, more tightly arranged, with the ability to differentiate the cell groups, which is the interstitial meristematic tissue.
The result of its activity is the main cause of nodulation in cereal crops.
