GRAAL: Growth, Architecture, ALlocation: a functional-structural model to analyse the interactions between growth and assimilates allocation integrating processes from organ to whole plant

An integrated functional-structural model, called GRAAL, has been developed to simulate and analyse the interactions between morphogenetic processes and assimilate partitioning during the vegetative development of individual plants. GRAAL associates models of plant morphogenesis and models simulating the growth of plant compartments as related to assimilate availability. Using objectoriented methods, knowledge is formalized at the organ level (i.e., local rules of development and functioning). The behaviour of the plant arises from interactions between the organs and the integration of the processes within the whole plant. Shoot and root organs are initiated as a function of temperature. Using the source–sink concept, organ growth is calculated from its potential growth and assimilate availability within the whole plant. In the case of maize plants as regards carbon assimilates, simulation results indicate that the model reproduces the main features of plant functioning (e.g., kinetics of root:shoot ratio for carbon, changes in priority between organs and plant plasticity to carbon availability). More generally, the model is a generic framework for testing and sorting hypotheses on processes involved in plant development. In this respect, it is an integrated ecophysiological tool for analysing the interactions between genotypic and environmental characteristics affecting plant behaviour