Pharmaceutical Botany Experiment

Author: Chief Editor: Wang Le Original
Publisher:
Publish Date: 2003-08-01
Features: Preface This book is a supplementary experimental textbook for the planned teaching material "Pharmacognosy" in general higher vocational education for pharmacy. The book is arranged with 13 experiments, among which 11 experiments are about morphology and anatomy, covering the morphology and structure of plant cells, tissues, and various organs; 2 experiments are about taxonomy, covering the use of keys and the identification methods of unknown plants.
Excerpt: Then use forceps to hold one side of the cover slip, or hold the adjacent two corners of the cover slip on both sides of the thumb and index finger, so that the underside of the other side of the cover slip contacts the water drop on the slide. Finally, gently lower the opposite side. This method of covering is to avoid the formation of bubbles under the cover slip. However, if the operation is not performed properly, a small amount of bubbles may still form. In this case, you can gently press the cover slip with the other end of the pencil to expel the bubbles, or remove the cover slip and redo it. After removing the bubbles, if water is found to overflow under the cover slip, use blotting paper to absorb the overflowed water; if water is found not to fill a certain space under the cover slip, use a dropper to add distilled water to that space. Adjust the microscope to focus, place and align the slide specimen. While keeping the condenser position unchanged, gradually reduce the aperture while adjusting the focus of the low-power objective until you see many neatly and densely arranged bar-shaped cells, which are epidermal cell groups. Since the epidermal cells are colorless and transparent or semi-transparent, they are generally difficult to observe. Therefore, only those cells that are perpendicular to the field of view, making their cell walls less transparent, can be seen. These walls are the lateral walls of the cells, while the front wall, being parallel to the field of view, is not visible. To confirm the existence of the front wall and observe other basic structures inside the cells, the cell walls need to be stained. The method is as follows: Remove the slide from the stage and place it flat on the table. Carefully drop 1 drop of potassium iodide iodine solution near the left or right side of the cover slip on the slide (do not let it overflow the surface of the cover slip), allowing it to contact the water under the cover slip. Then, on the other side, use a small piece of blotting paper to contact the water under the cover slip. As the water is absorbed by the blotting paper, the potassium iodide iodine solution enters the space under the cover slip. When the epidermis under the microscope is partially or fully stained yellowish-brown, observe the stained area with the low-power objective. The front wall of the epidermal cells appears light yellowish-brown, proving the existence of the front wall (this reagent only stains the cell walls). Inside the stained cells, it is generally possible to see oval-shaped objects with a darker yellowish-brown color, which are the nuclei. They appear yellowish-brown and have a darker color because we are viewing them through the yellowish-brown "glass" of the cell wall, and their transparency is much lower than that of the cell wall. To distinguish between cytoplasm and vacuoles, switch to the high-power objective. It can be seen that, except for the nucleus, the rest of the internal parts of the cells are relatively light in color. This part can be further divided into two parts based on color and other characteristics: relatively darker, containing many small granular substances, and slightly viscous, which is the cytoplasm; relatively light or very light, without granular substances or other visible substances, and appears more dilute and clean, which is the vacuole. There is no clear boundary line between the two, and their positions are not fixed. The cytoplasm is often distributed close to the cell wall, with the vacuole occupying the inner part; sometimes, the cytoplasm can also be distributed inward, dividing the vacuole into several parts (Figure 2).
Four. Assignments
1. If turning the coarse focus wheel on the microscope you are using can bring the low-power objective close to the stage so that the bottom of the low-power objective is at the same plane as the upper surface of the stage, then after placing and aligning the slide specimen, how can you ensure that the slide specimen will not be crushed when focusing with the low-power objective?
2. When using the high-power objective to observe the slide specimen, if you do not first focus with the low-power objective but directly focus with the high-power objective, do you think it is more difficult to avoid crushing the slide specimen? If you think it is not difficult to avoid, please describe your operation method; if you think it is difficult to avoid, please explain the reason.
3. Some microscopes, after focusing with the low-power objective, require rotating the fine focus wheel in the direction that brings the high-power objective closer to the slide specimen to focus correctly. If you rotate the fine focus wheel in this way and after turning it one full circle, the image still does not appear in the field of view, what will you do?
4. Draw 1–2 epidermal cells observed, labeling the cell wall, nucleus, cytoplasm, and vacuole.
Experiment Two: Identification of Cell Inclusions and Cell Wall Properties
I. Objectives and Requirements
1. Master the basic characteristics of starch grains.
2. Recognize the common types of calcium oxalate crystals.
3. Understand the microscopic chemical methods for identifying cell wall properties.
4. Initially master the technique of hand-sectioning and the hydrate chloral permeation method.
II. Materials, Instruments, and Reagents
Potato tuber, rhizome powder of Rheum palmatum, rhizome powder of Pinellia ternata, young stem of Cinnamomum camphora (grown in the spring of the same year). Microscope, slides, cover slips, fruit knife, white gauze, double-edged razor blade, forceps, dissecting needle, culture dish, matches (or toothpicks), alcohol lamp, blotting paper. Glycerol acetic solution, dilute glycerol, hydrate chloral solution, zinc chloride iodine solution, phloroglucinol solution, concentrated sulfuric acid, Sudan III solution, distilled water. Preparation method of glycerol acetic solution (Scheele's solution): Take equal amounts of glycerol, 50% acetic acid, and distilled water, mix well; preparation method of dilute glycerol: Take 1 part glycerol and add 2 parts distilled water, mix well. If it is to be used for a long time without rotting, a small amount of benzoic acid or phenol can be added; preparation method of hydrate chloral solution: Take 50g of hydrate chloral and dissolve it in 20ml of distilled water; preparation method of zinc chloride iodine solution: Take 13g of zinc chloride and dissolve it in 20ml of distilled water, add 1g of iodine and dissolve, then add 40g of zinc chloride and dissolve again; preparation method of phloroglucinol solution: Take 1g of phloroglucinol and dissolve it in 100ml of 95% ethanol; preparation method of Sudan III solution: Take 0.5g of Sudan III and mix it with 100ml of 95% ethanol.
III. Content and Methods
(1) Observation of Starch Grains
Drop 1–2 drops of glycerol acetic solution onto a clean slide. Use a fruit knife to cut a part from a complete potato stem, and then gently scrape the cut surface with a blade perpendicular to the cut part. Quickly immerse the blade that has scraped the potato in the glycerol acetic solution on the slide, stir slightly, and then remove it. Cover with a cover slip. Place under the low-power objective of the microscope already focused on light to observe the starch grains. During focusing, when some near-elliptical, near-circular, or irregular-shaped colorless particles appear in the field of view, immediately focus accurately. Then gradually reduce the aperture from its original maximum (at the same time, the condenser should be at its highest position), while observing the particles in the field of view. When some particles show a ring-like texture with one ring inside another, stop adjusting the aperture. At this point, it can be confirmed that these particles are starch grains, and the ring-like texture is the layer. In the core surrounded by the layer, there should be a hilum. However, the hilum of potato starch grains rarely appears black and prominent as drawn in the book, but is often faintly visible because it is the relatively lighter part of the entire starch grain.