In order to understand developmental processes in a complex system like a plant, it is necessary to analyze parts of the system individually. Thus, in the preceding chapters the shoot apex as the initiating center of the shoot has been examined in detail, as have the initiation and development of the lateral organs to which it gives rise. The full significance of the processes that occur in these parts, however, can only be appreciated in the context of the integrated system in which they occur. It is appropriate now, therefore, to consider the development of the whole shoot system. Reflection upon the enormous diversity of shoot forms might seem to make this an impossible task, but fortunately the emergence of concepts of shoot architecture has established a framework for the analysis of varied patterns of shoot ontogeny. A relatively small number of developmental processes, occurring in various combinations, provide interpretations of widely divergent shoot forms.

This chapter will consider first the sequence of events by which the individual shoot is elaborated to its final form. It will then examine different developmental potentialities that may be expressed by shoots, often within the same shoot system. The ways in which different shoot expressions fit together into integrated shoot systems will be examined in terms of architectural concepts. Finally, these concepts will be used to interpret some of the major plant growth forms, such as trees, shrubs, and herbs.