MODELING PLANT-GROWTH AND ARCHITECTURE - SOME RECENT ADVANCES AND APPLICATIONS TO AGRONOMY AND FORESTRY

Modelling plant structure an growth has undergone major changes in the last decades along two major lines: the integration of ecophysiologic al knowledge in process-based models which often lack a description of plant topology and geometry, and the generation of 3-D virtual plants using morphogenetic models which simulate the architectural developme nt in a stable and homogeneous environment. There is now a trend to me rge these two approaches, that is to link plant architecture and funct ioning. This trend is based on the recognition that plant structure: ( i) is the joint output of the physiological processes (water and carbo n balance, etc.) and the morphogenetic programme of the plant, (ii) de termines the external environment of the trees which itself regulates their functioning (competition for space, light attenuation, etc.), an d (iii) directly conditions the physiological processes within the tre e (hydraulic structure, self-shading, allocation of photosynthates, et c.). Such models can be used in agronomy and forestry in various ways: to investigate the effects, local and global, immediate and delayed, of the biophysical environment on plant morphogenesis and yield; to st udy light attenuation through the canopy, to analyse the transport of water and the allocation of photosynthates within the plant; to analys e the competitive interactions among different plants in the same stan d; to calibrate remote sensing techniques and to visualize large lands capes.