AbstractsChemistry

The classification of plants has involved an enormous amount of work on the part of a large number of botanists. It is based on the natural affinities of plants- and has been guided by the concepts of evolution. The tools of the taxonomist have been mainly morphology, anatomy, embryology and palaeontology. However, in many cases it has been impossible to construct accurate phylogenetic relationships. It becomes important, therefore, to discover additional means whereby some of the problems of taxonomy may be resolved. As Gibbs (33) and others have pointed out, the comparative chemistry of plants provides another source of evidence for the determination of their relationships and it has been shown, in a number of cases, that there is a correlation between certain aspects of the chemistry of plants and their arrangement in a natural system based on morphological or other studies. In 1944, Creighton, Gibbs and Hibbert (20) found that there are significant differences between the lignins of some of the major groups of vascular plants. Their conclusions were based on the recovery of certain phenolic aldehydes from alkaline nitrobenzene oxidised lignins. Thus, the Angiosperms and the Gnetales gave syringaldehyde and vanillin on oxidation, whilst the Coniferales, with few exceptions, Ginkgo biloba and the ferns gave only vanillin. [...]