Comparative Biosynthetic Pathways in Higher Plants

During the last ten years or so, variation in secondary plant products between different taxa has been increasingly used in systematic and evolutionary studies. However successful this approach has been, it now needs to be tempered by a consideration of the underlying variation in the biosynthetic pathways leading to the compounds in question. In some cases cognate compounds are formed by two or more pathways in different taxa; in others the same biosynthetic route is regulated in different ways. It is necessary, therefore, to examine the ontogeny and characteristics of the individual enzymes involved. Examples of such approaches are given for a large number of different classes of compound. including naphthoquinones, flavonoids, rneta-carhoxv aromatic amino acids, branched chain sugars and lignin.