The art of preparing botany samples

Fabrication of a botanical preparation is not that easy.

It is a lengthy and laborious activity to make a botanical preparation as is shown in the images. It is quite an art to maintain the natural shape of the material, to cut the section as thin as possible, color it, and keep the loose parts of the flower bud in place. We will not go into too much detail about the necessary procedures to achieve a good result. All this has extensively been described in the relevant literature.

Briefly summarized, the following steps are generally taken:

• Fixation of the plant material with for example alcohol, an alcohol glacial acetic acid mixture, or a formaldehyde solution. This must be done in such a way that the material does not lose its natural shape due to shrinking. After fixation, the fixative must be washed out.

• If necessary, the fixed material can be stored longer in alcohol, glycerin, and water mixture.

• In the botanical microtechnique, the embedding of the fixed material in paraffin is most commonly used before cutting very thin slices out of it. Before embedding, the water must be removed from the material with a solvent such as alcohol.

• Before embedding in paraffin, the material can be clarified if necessary using certain solvents.

• The material now enclosed in cubes of paraffin, is cut into micrometer thin slices, the so called coupes, using a slide or a rotary microtome. These are equipped with razor-sharp knives.

• The resulting coupes are attached to an object glass using a special adhesive. The coupe is stretched by careful heating so that it lies as flat as possible on the object's glass. The paraffin is then washed out with a solvent.

• Then the various structures in the coupe are colored. There are many coloring methods available, which make it possible to distinguish structures in the coupe with their typical functions. After coloring, the coup must be made free of water before the next step.

• In order to preserve the preparation for ‘eternity’, the coup is embedded in a mounting agent. The mounting agent is usually a natural or synthetic resin.

• During embedding, the coup is covered with a coverslip, heat may also be added to allow the mounting agent to flow properly. The trick is to avoid the inclusion of air bubbles.

Fig. 1 - Male pine cone seen under the Motic Panthera C microscope, Plan UC 2X, Moticam ProS5 Plus

Fig. 2 - Male pine cone seen under the Motic Panthera C microscope, Plan UC 20X, Moticam ProS5 Plus

Fig. 3 - Male pine cone seen under the Motic Panthera C microscope, Plan UC 40X, Moticam ProS5 Plus

Fig. 4 - Male pine cone seen under the Motic Panthera C microscope, Plan UC 60X, Moticam ProS5 Plus

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