Distribution of latex in the plant kingdom

Abstract

In conclusion it should be remembered that the purpose which latex serves in the metabolism of the plant has not been conclusively established. We must also remind ourselves once more that the term ‘latex’ is used in a very loose sense, and the line of demarcation between latex itself and certain other secreted metabolites is by no means clearly defined. It is commonly held that latex is no more than a waste product of metabolism, but, if this is so, it is all the more surprising that laticifers in some at least of the Papaveraceae contain such specialized chemical substances as alkaloids at a very early stage of their development, as Professor Fairbairn’s valuable work (11) has so clearly shown. The mere fact that the latices of different kinds of plants vary in their microscopical appearance and chemical composition suggests that they may not always have the same metabolic significance. Furthermore, the fact that latex is restricted to a small number of plant families, between many of which there is no evidence of close taxonomic relationship, suggests that the capacity to produce latex has been evolved more than once. To the systematic anatomist it seems that there are many morphological entities in the structure of plants, of which laticifers are hut one example, whose existence provides evidence of important underlying differences in metabolism. We are too apt to assume that the metabolism of all photosynthetic plants is uniform. No doubt a basic uniformity exists, but the restricted occurrence of plants with unusual products of metabolism such as latex shows that there is great scope for the study of comparative physiology and chemotaxonomy in the future.