171 Incorporation of 3D Plant Structures in Genetic and Physiological Models P.H.B. de Visser, L.F.M. Marcelis, G.W.A.M. van der Heijden and G.C. Angenent Plant Research International (PRI) Wageningen The Netherlands J.B. Evers, P.C. Struik and J. Vos Crop and Weed Ecology Group Wageningen University, Wageningen The Netherlands Keywords: Chrysanthemum, Arabidopsis thaliana, carbon dynamics, gene expression, L-system, virtual plant, morphology, simulation Abstract The recently developed virtual plant modelling approach has strongly increased the potential of model applications in crop sciences. Virtual plants are based on a new modelling concept and are generated in a 3-dimensional (3D) virtual space. The technique facilitates the incorporation of 3D environmental effects on plant growth and development. The methodology to generate virtual plants is described for Arabidopsis flower mutants and for Chrysanthemum plants. The profiling method was used to create 3D images of existing plants by merging 2D digital pictures of the plant silhouette to a 3D object. The data from the digitised plants were used to calibrate an architectural model for Arabidopsis, based on the L- systems algorithm. This architectural model was able to simulate the morphological differences between a number of plant genotypes. On the basis of L-systems, a prototype architectural model was made for Chrysanthemum. The L-system calculated temperature driven growth and light interception on the basis of radiosity. A method is presented to link this 3D model to a physiological growth model to incorporate effects of carbon dynamics. The first results show that the combined strength of both models may help to understand and visualise plant growth and appearance. INTRODUCTION Few studies have incorporated the visualisation of 3D plant structures in genetic and -growth models (e.g. Sievänen et al., 2000). The number of possible applications for this is rapidly increasing as a consequence of powerful 3D tools that can facilitate the incorporation of 3D functionality. The L-system formalism is able to generate detailed and realistically visualised 3D plants on a computer screen, referred to as ‘virtual plants’ (Prusinkiewicz et al., 1999). The L-system is used in this paper as a basis for two case studies. Effects of Genes on Morphology To understand the way genes affect plant form, many studies have used mutations of the gene in question to show its effect. For Arabidopsis this research resulted in much information on its genetic pathways (Blázquez et al., 1998). There is a vastly increasing genetic database which requires an easy method of accessing the information concerning specific genotypes. This method may be realised in the form of these new 3D tools. The visualisations used up to now were restricted to schematic 2D representations of the plant or organ form. If the reported effects of genes on morphology could be modelled in 3D, this may contribute to our understanding of the spatial occurrence and outgrowth of tissues and organs. An example is modelling the form of Antirrhinum flower petals which could only be done with the aid of a 3D dynamic model on petal shape development (Rolland-Lagan et al., 2003). The MADS-box genes A, B and C control the flower morphology in Arabidopsis and many other species. These floral organ identity genes are responsible for the formation of sepals, petals, stamens and carpel of the Arabidopsis flower (Coen and Meyerowitz, 1991). Blocking the expression of one or more of these Proc. Int’l. WS on Models Plant Growth & Contr. Prod. Qual. in Hort. Prod. Eds. M. Fink and C. Feller Acta Hort. 654, ISHS 2004