A plant's program of architectural development can be a powerful driver of phenotypic integration, and architectural plasticity an important mechanism behind integrated trait responses. In order to assess architecture's contribution to overall trait integration, I simulated architectural growth computationally using several realistic models consisting of combinations of branching, elongation, and meristem-identity rules. Architectural plasticity was embodied in the rules themselves and was expressed as the architectural response to simple simulated environmental variables. In contrast to many plant-growth simulations, mine was based exclusively on individual metamer behavior: architectures, trait correlations, and trait reponses all emerged from the iterated application of rules to each metamer of the simulated plant in each time-step of the simulation. The architectural program's contribution to trait and plasticity integration was assessed by changing rule parameters and observing changes in traits, their correlations, their plastic responses, and the correlations among the responses. Architecture was responsible for strong correlations among many architectural and life-history traits, correlations which persisted across environmental conditions but which differed when rule parameters or the rules themselves were changed. The rules with the greatest integrating effect were those that defined the control of flowering. Rules that defined branching frequency or the duration of meristem viability had relatively little integrating effect. That architecture should play a large role in trait and plasticity integration is unsurprising given the importance of other types of developmental linkage. That architectural rules differ in their effect suggests that the dissection of architecture is an important early step in the study of architecture's evolutionary and ecological consequences. Given how straightforwardly the architectural program can be described computationally, simulation should prove to be a useful tool both in the definition of architectural models and in the elucidation of their importance.

Key words: architecture, development, phenotypic integration, phenotypic plasticity, simulation, trait correlations