Have you ever glanced through a microscope in your school laboratory? If you look at a slide of plat stem through the microscope, you will be amazed to see the minutest details in cell. Botanists study the internal structure of plants mainly by examining their cross-sections under a microscope. These thin slices can tell us a lot about the structure of the cells that make up the plant and how they vary in different parts of the plant.
Internal Structure of Plants
In 1665, a scientist named Robert Hooke looked at a piece of cork under microscope and saw that it was made up of many tiny compartments. He named them cells and this term has been in use eve since. The equipments needed for obtaining the sections include a sharp razor, a small fine brush and a number of watch glasses and microscopic slides.
The sharp razor is used to cut off thin slices of plant stem as required. Cross-sections as well as the longitudinal pieces are obtained in the same manner. In case of fresh material, to obtain best results, the razor and the material must be kept moist with water. It should be cleaned with alcohol if the specimen is a preserved one.
To prevent shrinkage, the sections are brushed with water or alcohol. For quick examination, the sections are placed on a slide with drop of glycerin. The thin ones that show the cells clearly can be obtained for permanent use.
Staining is a process of adding dyes to observe the various tissues in different colors. The razor-cut sections are placed in alcohol and then dipped in a mixture of stains and alcohol.
After some time, the sections are transferred to a series of watch glasses full of alcohol. This removes water and the excess stain. The alcohol is removed by dipping the sections in clove oil or benzene. The section is then placed on a clean glass slide with a drop of Canada balsam resinous glue). A thin glass is added as a cover ship and sealed by warming the balsam of harden it. The slide, properly labeled, can then be stored and examined whenever required.
Details of time exposure for staining varies with the stain and materials used. The information can be collected form a textbook or worked out by practice. In laboratory analysis, many modern techniques are being adopted for in-depth studies on the subject.
