The chemical relationships of plants
When Linnaeus classified plants, animals and rocks, he used their morphological characteristics. For example, he looked at a flower and counted the number of stamens and pistils, and put all the plants with, for example, five stamens in one group, all those with four in another. It is not a natural system but it was better than the systems that existed earlier. He got the idea after having studied lots of different kinds of flowers and having read what other botanists had written.
As evolution has proceeded, plants have developed and new species have appeared. It is not just the exterior of plants that has changed, but also the interior. The reason for the change can be found in the plants’ DNA which, in its turn, affects many enzyme systems. Plants can then produce other chemical substances that assist in coping with the demands of the environment. It may be that substances produced by the plant can provide defence against insects, larger animals, bacteria, viruses, and fungi.
Evolution has thus caused plants to develop, not only differences in appearance, but even chemical differences. The difference between a wood anemone and a blue anemone is not just appearance but also their content. Different plants contain different chemical substances. But there are also similarities. Plants that are closely related often contain chemically related substances. That is why all kinds of foxgloves contain poisonous, cardio-active substances. It is often a result of their living in similar environments where, for example, the development of a certain defensive mechanism can assist in the survival of the plant.
By examining all the details of the look of plants, their chemical constituents and enzymatic activities, it is possible to make a more precise study of the relationship between plants.