SIMULATING SOURCE-SINK CONTROL OF CARBON AND NUTRIENT TRANSLOCATION IN A MODULAR PLANT

Modular structure has important consequences for the control of intern al resource translocation in plants, and for the decisions concerning growth of plant parts. Some plant parts may act as partially autonomou s functional modules with their own resource supply and localized cont rol of growth. Resources for growth are obtained from sources (e.g, ph otosynthesizing leaves) and are translocated to sinks (e.g, growing me ristems). Resource translocation between sources and sinks is determin ed by the sink strength of growing meristems, which involves a concent ration local changes in the allocation of resources. compete for a lim ited resource supply, then more resources are Herbivory and other fact ors that affect sources or sinks may cause This paper presents a simul ation model that takes into account modular plant structure and its co nsequences for source-sink dynamics and growth. In simulations, Scots pine (Pinus sylvestris L.) is described as a data structure tree, wher e the tree nodes represent individual pine shoots and the links betwee n the nodes serve as routes for carbon and nitrogen translocation, A p ractical property of this approach is the partial autonomy of pine bra nches. Each simulated shoot has its own sink strength and physiologica l processes determining its resource intake. Resource translocation be tween the shoots of the simulated tree is controlled by the sink stren gths of the existing translocation routes. To demonstrate the applicab ility of this simulation approach for questions concerning source-sink dynamics, we have simulated some herbivory treatments, local defoliat ions and debuddings of pine shoots, and compared the results with corr esponding field experiments. The qualitative outcomes of simulated and experimental treatments follow the same general patterns.