Simulating source-sink control of carbon and nutrient translocation in a modular plant

Modular structure has important consequences for the control of internal resource translocation in plants, and for the decisions concerning growth of plant parts. Some plant parts may act as partially autonomous functional modules with their own resource supply and localized control of growth. Resources for growth are obtained from sources (e.g. photosynthesizing leaves) and are translocated to sinks (e.g. growing meristems). Resource translocation between sources and sinks is determined by the sink strength of growing meristems, which involves a concentration gradient from sources to sinks. If many sinks compete for a limited resource supply, then more resources are proportionally allocated to the strongest sinks. Herbivory and other factors that affect sources or sinks may cause local changes in the allocation of resources. aper presents a simulation model that takes into account modular plant structure and its consequences for source-sink dynamics and growth. In simulations, Scots pine (Pinus sylvestris L.) is described as a data structure tree, where the tree nodes represent individual pine shoots and the links between the nodes serve as routes for carbon and nitrogen translocation. A practical property of this approach is the partial autonomy of pine branches. imulated shoot has its own sink strength and physiological processes determining its resource intake. Resource translocation between the shoots of the simulated tree is controlled by the sink strengths of the existing translocation routes. onstrate the applicability of this simulation approach for questions concerning source-sink dynamics, we have simulated some herbivory treatments, local defoliations and debuddings of pine shoots, and compared the results with corresponding field experiments. The qualitative outcomes of simulated and experimental treatments follow the same general patterns.