Botany

How to Examine a Plant Specimen



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Examining a plant specimen takes skill and practice but you can learn to perform examinations with ease and efficiency. Plant specimens are examined for many reasons. It might be to identify the plant itself or to classify a new specimen. It may be to analyse the plant for symptoms of disease or pests. It might also be to confirm which species it is from a genus in order to decide if it is an invasive, natural or poisonous specimen.

Some genus such as umbeliferae have several similar looking plants and only examination can tell which species you have. This can be an important factor if you have the plant on pastures where it might poison grazing animals and you can decide if it is worth the cost of spraying or if the plant is harmless. Whatever the reason, there are certain procedures to follow during the examination.

First, set the plant specimen out so you can clearly see the different parts. Taking a white board, divide the plant into leaves, stems, roots, flower buds and, if possible, open flowers and seed parts.

Starting from the bottom up, examine the roots. Look closely and see if there is a tap root or if the plant has a fibrous root system. If it has a tap root, is it long, tapered or round in shape and does it have branched smaller roots or many root hairs? These characteristics will help narrow the plant within its genus.

Next, look at the stem. Is it rounded or ridged? Is it hairy or does it have adaptations like thorns or needles along it? Is it green or a different colour and is it woody or not?

Now examine the leaves. Are the margins entire or toothed? Do the veins run parallel to the midrib or branch from it? This will tell you if it is a dicotyledon or monocotyledon. Are the leaves long and strap-like with entire margins? If so the plant is a monocotyledon. Are the leaves waxy or hairy?

Still looking at the leaves, does each leaf arise from a single stem or do several smaller leaves (leaflets) arise from a point? Are the leaflets arranged opposite each other or alternately?  All these characteristics should help you to narrow down your plant identification. Do the leaves have a stalk or do they arise from the stem (sessile)?

Next look at the flower buds - are they thick, waxy, brown, dry, moist or covered in sticky secretions? Do the flowers inside have petals, sepals or tepals and are the petals coloured? 

Putting all these characteristics together, you should now be able to list the root type, leaf type, stem characteristics, flower and bud characteristics and be able to identify the plant from your examination.

More in-depth examinations can be made by preparing slides to reveal the inner tissues such as palisade, mesophyll and specially adapted cells like aerenchyma, which only certain plants (water living ones) possess which will help further examination and identification.

The examination of plants is fascinating and can be the key to identifying completely new species. Most examinations can be done simply using nothing more than a magnifying glass but some need more specialist equipment due to their size or the need to look at cells. Whichever way you do it, examination of plants can be easy and can reveal so much about plants to us and perhaps share a few of their secrets.

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