A Model of Poplar (Populus sp.) Physiology and Morphology Based on Relational Growth Grammars

Functional-structural plant models (FSPMs), combining the physiological function of a plant with its architecture, require precise and transparent specifications. This can be seen as a new challenge to the design of programming languages. Here we introduce, exemplarily for a model of young poplar trees, our new formalism of relational growth grammars (RGGs), which extend the well-known Lindenmayer (L-)systems to a specific sort of node- and edge-labelled graph grammars. The model has been written in the programming language XL, which extends standard Java by rule-based programming with RGGs and overcomes many of the disadvantages of L-systems. RGGs can bridge different scales: In our model, morphogenetic rules in L-system style are combined with rules describing a regulatory network of hormone biosynthesis and rules updating photosynthate concentrations of shoot modules, all in one and the same formalism.