The evolution of chemosystematics.

Chemosystematics has been used to distinguish plants and other organisms that are useful for food and those best avoided. Originally unwritten, this knowledge has been progressively formalized with useful, harmful and inactive chemical constituents from relevant taxa now identified and recorded. This knowledge has led to insights into taxonomy of these plants, animals and micro-organisms. Advances in analytical instrumentation, in particular chromatography, followed by electronic detection methods, have speeded these studies, culminating in metabolic profiling, ("metabolomics"). The huge array of chemical constituents isolated from plants combined with morphological and cytological data take their place as part of the overall Natural History of the organism in its environment. The study of, DNA (genomics) and to a certain extent m-RNA (transcriptomics) and proteins (proteomics), has led to the immense subject of molecular biology which relates the phenotype of a taxon to its genome. This type of chemosystematics on its own does not of course describe the small molecules in plants, often called, perhaps misguidedly, "secondary compounds", or how they relate to each other, to the plant containing them or to the environment. Economic uses flow from this knowledge, such as the topic of non-protein amino acids and amines, which from 1958 to the present has produced information from the chemotaxonomic to the severely practical. Literature on the subject from 1909 to the present charts developments in the discovery of new compounds and their use in systematics. Often a mere catalogue, a list of plant constituents is nevertheless part of the overall description of a plant.