Anatomical changes during adventitious root formation

Abstract

Organization is one of the most characteristic traits of living organisms. It is especially conspicuous in the orderly growth that every organism undergoes and which produces the specific forms so characteristic of a particular species [1]. The evidence for biological organization is manifested in studies in which the normal processes of growth and development are modified experimentally, e.g. by removing parts of the growing body. Thus, a ‘cutting’ removed from a plant, under appropriate conditions, may produce a new root system and finally an entire individual with a balanced ratio of root to shoot. These regeneration processes are present in a great range of plants. Roots that originate in locations other than from the embryo or as branches of the primary root are termed adventitious [2, 3]. They may arise spontaneously on intact plants, especially at nodes of prostrate stems and on rhizomes, or stolons or they may develop only as a response to damage when part of the plant has been deliberately or accidentally severed from the existing root system. This involves various anatomical changes associated with wound responses in addition to those involved in root formation itself. Adventitious roots are produced vigorously and rapidly in some species under appropriate conditions, but much less readily in others, and plants can be grouped according to their ease of rooting (Fig. 1).