HYBRIDIZATION AND THE EVOLUTION OF PLANTS

Summary Polyploidy — both auto‐ and allo — may have dominated the short term evolution of plants because it increases “biochemical versatility” at the primary enzyme level. It actually creates new enzymes with different properties which may extend the range of environments in which normal and successful development may occur.. The new enzymes arise by oligomerisation of related polypeptides produced by related (homoeologous) genes (“hybrid” enzymes). Further study of polyploids may help us understand more about the control of development of the phenotype. There is evidence that the concentration of different isoenzymes changes with the development of tissues. Whether this denotes a causal connection between differentiation and enzyme production, we do not know. But the presence of isoenzymes generated by polyploidy may have allowed such controls to be made more refined and delicate and, thus, helped in ecological success. The determination of the actual amino‐acid sequences of such enzymes may, in the future, perhaps contribute to a further understanding of the role of enzyme hybridization for biochemical versatility as a factor in evolution.