Plant mature tissue observation experiment
Plant mature tissue observation experiment
Source of content: Microbiology Lab.
Operation method
Plant mature tissue observation experiment
Principle
1. to understand the morphology, location, structure and function of various mature tissues of plants. 2. to understand the interconnections between different tissues, structure and types of vascular bundles, and the method of isolation of plant tissues.
Materials and Instruments
Sweet potato leaves Neem branches Radish root tips Potato tubers sliced crosswise Pumpkin stems sliced longitudinally and crosswise Tilia stems sliced Pear fruit Corn stems sliced crosswise Move I. Protective tissues For more product details, please visit Aladdin Scientific website.
Distilled water Fennel red Resorcinol Hydrochloric acid
Microscope Slide Coverslip Tweezers Blade Gauze block Mirror paper Absorbent paper Beaker Nylon gauze Glass rod Petri dish
1. Observation of the lower epidermis of the leaf
Take the sweet potato or broad bean leaves, the back side up, on the index finger of the left hand; with the middle finger and thumb clamp the ends of the leaf, use tweezers to tear off a small piece of epidermis, as a clinical slide, placed in low magnification microscope observation, can be seen in the epidermal cells set each other, the side wall was wavy, arranged tightly without cell gaps, the cells have a colorless and transparent cytoplasm and a rounded nucleus. In the epidermal cells distributed between many stomatal apparatus, choose a clearer stomatal apparatus, conversion of high magnification to observe carefully, it consists of two kidney-shaped defense cells and stomatal slits (no paracellular defense cells), pay attention to the observation of the characteristics of the defense cell primary wall and the chloroplasts contained in the defense cells.
2. Observe the pericarp of the stem
Take a neem branch and observe the white granular projections on its surface as lenticels.
With a fingernail to gently scrape off the outermost brown layer, that is, the cork layer, the inner surface of the green part of the inner layer of the cork, between the two for the cork layer, the three together known as the pericarp.
In local areas, the cork layer splits outward to produce thin-walled cells, forming secondary aeration organization (lenticels). Another transverse section of a linden stem was taken to observe the structure of the periderm.
After the observation, think: What kind of protective tissue are the epidermal cells of the leaves and the peridermis of the old stems? What are the morphological and structural characteristics of each of them in order to adapt to their protective function?
Thin-walled tissues
1. Absorptive tissue
Radish root tip to make a pressure piece, put under the microscope to observe the morphology and structural characteristics of the root hair.
2. storage tissue
Take a small piece of potato tuber, use a double-sided blade for freehand sectioning, select the thinner section on the slide, add 1 drop of distilled water and cover the coverslip under the microscope to observe the structural characteristics of starch storage cells.
3. assimilation tissue
Take the leaves of the oleander to make a freehand transverse section, make a temporary section specimen, and put it under the microscope to observe and understand the structure and function of the fenestrated and spongy tissues of the leaf flesh.
4. Ventilation
Observe the transverse section preparation of old rice roots, in the cortex of old rice roots there is a part of cell disintegration, forming a large cavity (air cavity), with the role of aeration, known as the aeration tissue.
Observe these thin-walled tissues and think: why are they also called nutrient tissues, basic tissues?
Third, the mechanical organization
1. thick horn tissue
Take pumpkin (or mint, apple, linden) stem cross section, first observed at low magnification, find the corners, and then change the high magnification from the outside and inside the observation, the outermost layer of neatly arranged flat cells for the epidermis, with multi-cellular epidermal hairs, immediately inside the epidermis in the cortex, there are several layers of green-stained cells, their cell walls in the corners and corners of the thickening, is living cells, and sometimes see the chloroplasts within the cells, for the Thick angular tissue.
2. Thick-walled tissue
(1) Fiber
In the thick horn tissue above the inner side, there are several layers of oval thin-walled cells, thin-walled cells, in its inner side there are several layers of cells dyed red, its cell wall is uniformly thickened and lignified, the cell lumen is small, there is no protoplasmic body, it is a dead cell, for the thick-walled tissues of the fibers.
(2) Stone cells
Take a small piece of fruit pulp near the middle of the pear, pick one of the sandy granular tissue on a slide, with the forceps handle will be scattered stone cell group pressure, add distilled water on the slide and cover with a coverslip to observe, can see the large thin-walled cells surrounded by darker stone cell group, its cell wall is abnormally thickened, the cell lumen is very small, with a clear pattern of holes.
Remove the preparation, a small drop of 40% hydrochloric acid on one side of the coverslip, on the other side of the absorbent paper to remove the water inside the coverslip, the material was hydrochloric acid soaked for 3~5 min, and then add 5% resorcinol alcoholic solution, placed under the microscope to observe, lignin in the stone cell wall can be seen in the lignin met with resorcinol to occur in a cherry-red or violet-red reaction (this method is commonly used in the test of identification of lignin in the composition of the cell wall).
After observation, think: the difference between the thick angular tissue and thick-walled tissue in which aspects? Analyze the relationship between its structure and function.
Fourth, the conductive tissue
1. xylem in the conductive tissue
Take the pumpkin stem longitudinal section under low magnification microscope to observe, the section of the central sides of some cell walls are stained red with a variety of thickening pattern into the tubular cells, they are a variety of types of conduit (tissue).
Each molecule of the conduit is connected to each other by a perforation formed in the end wall, and passes up and down. On close examination, the smaller arm diameter, the wall with spiral thickening and lignification for the threaded ducts, the larger diameter, with reticulate thickening and lignification for the reticulated ducts (note that in the section of some catheters or a section of catheters, because only cut to the middle of the lumen of the catheter, and therefore only see the catheter on both sides of the side wall and the middle cavity, but can not see the thickening of the pattern on the wall of the catheter).
Occasionally, annular conduits with very small diameters; with annular thickening and lignification of the walls can be seen in sections. Ducts are tubular structures that transport water; they are arranged in columns longitudinally within the xylem. Observe the structural features of the ducts and the differences between different types of ducts. Longitudinal sections of stems of mint, apple, etc. may also be observed.
2. Conducting tissues in the phloem
Observe the longitudinal section of pumpkin stems, distributed in the xylem inside and outside the two sides of the green stained mainly phloem, where you can see some of the caliber of the larger long tubular cells (each cell that is a sieve tube molecules) up and down and the formation of tubular structures, that is, for the sieve tube.
Changing to high magnification can be seen where the end wall connecting the upper and lower two sieve tube molecules is slightly enlarged, stained darker, can see the horizontal or inclined end wall, that is, the sieve plate, and in some cases, you can see the sieve holes on the sieve plate.
Sieve tube without nucleus, its cytoplasm often contracted into a bundle, away from the side wall, wider at both ends, narrower in the middle, which is the protoplasmic filaments through the sieve holes, thicker than the intercellular connecting filaments, especially known as contacting stoand (connecting stoand).
In the sieve tube next to the immediate vicinity of one to several darker stained, elongated companion cells. These companion cells have dense cytoplasm and nuclei. Sieve tubes are tubular structures that transport organic nutrients, and they are arranged in longitudinal rows in the phloem.
Observe the characteristics of sieve tube structures. Observe also longitudinal sections of stems of mint, apple, linden etc.
Think after observing: How can xylem and phloem be distinguished in longitudinal and transverse sections of stems? What are the differences between the ducts and sieve tubes?
V. Structure and types of vascular bundles
1. infinite vascular bundle of dicotyledonous plants (open vascular bundle)
Take the pumpkin (or other double in leaf plants) stem cross section to light naked eye observation, see the pumpkin stem section in the center of the star-shaped medullary cavity, around the medullary cavity of the thin-walled tissue there are five larger and five smaller vascular bundles are arranged in close proximity to each other.
Under the low magnification microscope, a large and clear vascular bundle was selected for observation, and it was seen that the vascular bundles were divided into four parts from the outside (by the outer side of the stem) to the inside, namely, the outer ligamentous part, the formation layer, the xylem and the inner ligamentous part. The xylem consists of two to three large diameter reticulated ducts with cell walls stained red and several small threaded or ringed ducts, tubules, and wood thin-walled cells with cell walls stained green. On both the inner and outer sides of the xylem, the smaller cells, stained green, are the inner and outer phloem.
The outer phloem was selected and carefully observed with a high magnification lens. It is composed of sieve tubes, companion cells and bast thin-walled cells. The sieve tubes are polygonal with a large diameter, and in some cases a single sieve plate with sieve holes in the end wall can be seen. Next to the sieve tube is a small cell with dense cytoplasm and darker staining in the form of a triangle or trapezoid, which is the companion cell. Within the phloem, the large cells without companion cells are phloem thin-walled cells. Between the outer phloem and xylem, there are several layers of tightly arranged flat, nearly rectangular shape and more regular cells, for the formation of the layer area. The formation layer is a lateral meristematic tissue, its cell division can make the vascular bundles expand.
Between the inner phloem and xylem there are also formation layer cells, but without the ability to divide. Because of the formation layer in the pumpkin stem vascular bundle, it is called infinite (open) vascular bundle, and because it has two inner and outer bast, so it is also called double bast vascular bundle, the whole name is double bast infinite vascular bundle.
2. Finite vascular bundle of monocotyledonous plants (closed vascular bundle)
Take corn stems (or rice stems) transverse section observation, can be seen in the basic tissue scattered with many vascular bundles.
Select a large and clear vascular bundle observation, can be seen around the vascular bundle there is a circle of thick cell wall, was stained red thick-walled tissue, known as the vascular bundle sheath. In the sheath against the outer part of the cell wall stained green for the phloem, the outer part of the primary phloem is mostly destroyed, the inner part of the posterior phloem in some larger polygonal cells for the sieve tube, in the sieve tube next to a smaller trapezoidal or triangular cells for the companion cells.
The inner part of the phloem is xylem with 1-2 small annular or threaded ducts, and the upper part of the v-shape is posterior xylem with a large perforated duct on each side.
There is no formation layer between xylem and phloem, so the corn vascular bundle is called limited (closed) vascular bundle, and because the phloem is arranged on the outside, so it is also known as the outer phloem vascular bundle or outer phloem limited vascular bundle.
Observe and think: Why are vascular bundles divided into infinite and finite? What are the differences in their structure and function?
Sixth, secretory structure
Compare and contrast the characteristics of various secretory structures
1. Transverse section of citrus rind to observe the secretory cavity. 2.
2. a cross section of a young pine stem to observe the secretory tracts (resin tracts) in the phloem and xylem. 3. a cross section of a dandelion root to observe the secretory tracts (resin tracts).
3. transverse section of dandelion root to observe the lactiferous ducts.
