Endospermic legumes are abundant in tropical forests and their establishment is closely related to the mobilization of storage polysaccharides and proteins. Tonini et al. adopt a systems approach to evaluate the effects of abscisic acid (ABA), ethylene and sugars on mobilization in Sesbania virgata during the period of establishment. They find that ABA appears to repress enzyme action and retard degradation of storage protein whilst ethylene has the opposite effect. Changes in concentrations of glucose and sucrose during this period suggest that ABA, ethylene and sugars interact to control the process of storage degradation and thus ensure a balanced flow of carbon and nitrogen to the developing seed.