Botany - B.Ye. Yakubenko 2017

Part One. Plant Anatomy and Morphology
Chapter I. Cytology
Laboratory Class Topic 1.1. Structure of the Microscope and Working Techniques with It

General Remarks. Laboratory and Practical Classes in botany are conducted using technical devices and various equipment, as well as herbarium, fixed, and living Materials. Magnifying glasses and stereoscopic microscopes are used for macroscopic examination, while light biological microscopes of various types and purposes are employed for the microscopic study of internal Structure. During laboratory sessions, microscopes such as the MBR-1 and Biolam models are most frequently used. With their help, students examine the Internal Structure of plant Cells, Tissues, and Organs, as well as individual phases and stages of their development. Therefore, a thorough knowledge of the Microscope and the techniques for operating it is a prerequisite for successfully performing laboratory work.

Object. MBR-1 or Biolam light biological microscope.

Task:

1. Thoroughly study The structure of the MBR-1 or Biolam microscope.

2. Master the technique of working with the microscope.

Equipment: MBR-1 or Biolam microscope.

METHODOLOGICAL GUIDELINES FOR Studying the Microscope and Operating Techniques. To study the internal structure of cells, tissues, and vegetative and generative plant organs, technical research tools are used, including magnifiers and microscopes of various purposes. Let us briefly review the STRUCTURE OF THE MBR-1 microscope. This Light Microscope consists of the following structural units: mechanical, illuminating, and optical parts (Fig. 11).

Mechanical parts. These include: 1) a massive base, which serves as the microscope's foundation and provides stability; 2) the limb (or carrying arm), which connects most PARTS OF THE microscope (and also serves as a handle for carrying it); 3) the revolving nosepiece with slots for screwing in objective lenses; 4) the body tube; 5) the coarse adjustment knob (or rack and pinion), which serves for coarse focusing and raising or lowering the microscope tube when working with low magnification; 6) the fine adjustment knob, which provides fine focusing to achieve a sharp image of the object at high magnification; 7) the stage, used for placing the specimen and botanical objects; 8) the substage bracket, used to raise the condenser; 9) the stage clips, which serve to fix the specimen on the stage.

Illuminating parts. These include: 1) a mirror with flat and concave surfaces; 2) a condenser, consisting of several lenses that concentrate and intensify the beam of light reflected from the mirror; 3) an iris Diaphragm, used to regulate the flow of light reflected from the mirror.

The optical parts of the microscope include oculars (eyepieces) and objectives. An eyepiece is a metal or plastic mount containing several lenses. Magnification is indicated on the eyepieces by the numbers ×7, ×10, ×15, ×20. The objective also consists of a metal mount housing 8–10 lenses. They have different focal lengths, thus providing varying magnification. Magnification values are indicated as ×8, ×40, ×90. This means that a resolving power of 1.68 µm provides an eightfold magnification marked on the objective as ×8, a resolution of 0.52 µm provides 40-fold magnification, and 0.27 µm provides 90-fold magnification of the microscope objective. The total linear magnification of the microscope is determined by multiplying the objective magnification by the eyepiece magnification. The minimum microscope magnification value is 7 × 8 = 56, and the maximum is 90 × 20 = 1800.

Class="center">

Figure 11. Biolam light microscope

Knowledge of the microscope's structure is a prerequisite for the quality investigation of botanical specimens and the execution of laboratory work. Once familiar with the structure of the microscope, one can proceed to operate it. First of all, it is necessary to master the basic rules of working with the microscope. Below are the most essential ones.

1. The microscope should be placed on the table at a distance of 3 cm from its edge, opposite your left shoulder. To the right of the microscope should be your notebook and a pencil case containing Glass slides, a dissecting needle, pieces of filter paper, a scalpel, forceps, a glass rod, and other necessary instruments.

2. Fully open the iris diaphragm to allow sunlight through and ensure the fullest possible illumination of the field of view.

3. Raise the condenser by turning the substage knob.

4. Raise the microscope tube by turning the coarse adjustment knob counterclockwise (upward). After raising the microscope tube 3–4 cm above the stage, turn the nosepiece so that the low-power objective is positioned opposite the opening in the stage. Check that it is set correctly by pressing it to the right and left. If it does not shift, it means the spring click of the objective lock holds it in the proper position. Lower the microscope tube until the distance between the objective and the stage is about 1 cm.

5. Set up the field of view. Depending on the light source and its brightness, select the appropriate mirror surface (usually the concave one) and direct the illumination source so that the rays reflected from its surface pass through the aperture of the iris diaphragm, the condenser lenses, the objective, the eyepiece, and reach your eye. You should look into the microscope with your left eye while keeping your right eye open toward your notebook. A brightly illuminated field of view will then appear before you in the microscope. This must be set up each time before beginning an observation.

6. Place your prepared or ready-made specimen on the stage so that the studied object covers the opening in the stage, or, if it is smaller, remains in the center of the field of view.

7. Looking with your left eye into the eyepiece and smoothly turning the coarse adjustment knob toward you, you will see the image. Focus it so that all details of the object are clearly visible.

8. Switching from low to high magnification is performed only after a sharp image has been obtained at low magnification. If you have not achieved this, do so by turning the coarse adjustment knob. Having obtained a clear image, grasp both objectives with your left hand and rotate the nosepiece so that the high-power objective marked with the number 40 or 90 is positioned opposite the stage opening. After that, very carefully and only by a fraction of a millimeter or micron, raise the microscope tube by turning the coarse adjustment knob toward you until the image appears. You will see the same object, but in a magnified view. Adjust the image sharpness by turning the fine adjustment knob to the right or left.

9. Select the best area of the specimen for investigation. For this purpose, use the mechanical stage control knobs located on both sides of the stage. The rear knob moves the stage forward and backward. At low magnification, to speed up the work, the specimen can be moved by hand.

10. Upon completing the work, use your left hand to return the nosepiece to a neutral position, remove the specimen, dismantle it, and wipe the glass slide and coverslip. Lower the microscope tube all the way down. Place the microscope into the cabinet in the spot marked with the microscope's number. Knowing the structure of the microscope and the rules of operating it, you can proceed to further studies of botanical objects. However, for this, you must master the technique of preparing slides. We will become familiar with it during The Study of The plant Cell.

Conclusion. The Current state of scientific research requires knowledge of the Water/140.html">Anatomical Structure of PLANTS AND THEIR constituent parts. This can be achieved only by using technical research tools, including light biological microscopes such as the MBR-1 or Biolam.

Self-Assessment Questions

1. What are the most essential parts of a microscope, and how should they be handled during operation?

2. Name the optical and illumination Components of the microscope.

3. Which parts belong to the mechanical system, and how are they operated?

4. What steps are required to set up the field of view?

5. How do you focus the microscope for high magnification? How do you switch from low to high magnification?

6. How can the linear magnification of a microscope be determined?

7. What are objective lenses and eyepieces? What are their magnification values?

8. What is the structure of the condenser, when is it used, and how?