Models of cotton plant architecture expressing several physiological hypotheses about plant resource use and responses to damage are incorporated in the traditional research cycle to investigate the phenomena of compensation for defoliation. Two separate approaches to modelling the uptake and allocation of carbon are used: a detailed bottom-up physiology model expressing ideas about local control, and a top-down, canonical approach where qualitative knowledge about plant responses to defoliation are modelled as flows between plant physiological compartments. The two models provide contrasting methods for developing explanations for the underlying pattern of responses observed in the plants.