For many years there has been a growing concern, particularly among researchers in biology education, about the extent to which research findings from one discipline (most usually physics education) can be applied directly to other disciplines (particularly biology education). This paper explores the issue through the use of one particular theoretical construct--Learning Demand--to inform the design of a plant nutrition teaching sequence. Reflections on this experience suggest that the basic construct could be applied to good effect but contextual differences between disciplines make it more difficult to agree common ground in relation to the finer detail. Implications for the development of a common framework for science education are considered. (Contains 3 figures.)