Determining the Influence of Plant Architecture on Light Interception of Virtual Rice Plants on the Simulation Platform GroIMP

Functional-structural plant models (FSPMs) combine the specification of 3-d structure and development of plants with simulation models of some of their functions and thus allow to assess the impact of 3-d architecture on plant performance. The availability and distribution of photosynthetically-active radiation is a key factor for photosynthesis and biomass production in all green plants. The open-source simulation software GroIMP provides a rule-based model specification language, XL, suitable to generate realistic time series of growing 3-d plant shapes, and a spectral raytracer which allows to estimate the amount of radiative power intercepted by each organ of the virtual plants, taking arbitrary light sources (direct and / or diffuse light) and spectral qualities into account. We designed a rule-based 3-d model of rice plants (Oryza sativa L.) during their vegetative growth phase and parameterized it for different cultivars, particularly, Yongdao 6 and Wuxiangjing 14. The model has a time step of 1 day. Internodes were modelled as cylinders and leaves as NURBS surfaces. A mechanical approach was used to estimate the bending of the leaves under their weight. Architectural parameters, like leaf shape and dimensions, leaf angle, number of tillers and number of leaves, were then varied in a continuum between the values which were reported for the existing cultivars, thus producing a large number of "virtually-bred" intermediate cultivars. In simulation experiments, we measured the total amount of intercepted light at the end of vegetative growth, i.e., at the onset of panicle formation. The optimal parameter combinations which we found could, after some validation and improvement of our model, guide the future breeding of rice for improved resource exploitation. However, in the moment our focus is still on the development of the virtual methods and tools rather than on realistic breeding scenarios.