Modelling plant structure and growth has undergone major changes in the last decades along two major lines: the integration of ecophysiological knowledge in process-based models which often lack a description of plant topology and geometry, and the generation of three-dimensional virtual plants using morphogenetic models which simulate architectural development in a stable and homogeneous environment. There is now a trend to merge these two approaches, that is to link plant architecture and function. This trend is based on the recognition that plant structure: (i) is the joint output of the physiological processes and the morphogenetic programme of the plant, (ii) determines the external environment of the trees which itself regulates their functioning, and (iii) directly conditions the physiological processes within the tree. Such models can be used in forestry in various ways