On the Initiation of Organization in the Root Apex

Abstract

Root and shoot apices are the major centers of organization in the development of the higher vascular plant. Apices are sites of origin of new cells formed by repeated cellular divisions in distinctive patterns; they serve as the organizers for the elaboration of tissue patterns in the continuing development of the mature axial structures of the root and stem. Apices are where things happen. Once formed, an apex, either root or shoot, is a remarkably stable structure, unperturbable in its activities of new cell formation and tissue pattern determination. Furthermore, it hides the secrets of its inherent organizational capacity remarkably well. We know very little about the properties of apices which allow them to be essentially autonomous in their functioning. Their activities are programmed in the genetic constitution of the cells of which they are comprised and the coordinated, multicellular tissue patterns which result from correlated intercellular behavior are equally referable to the genes. One of the basic problems of understanding organization in the vascular plants is to understand how apices operate, in what ways they are themselves organized and how this distinctive organization arises.

The author acknowledges the research work and helpful discussions of his graduate students and post-doctoral fellows but takes sole responsibility for the unsupported speculations included herein.