in plants, γ-aminobutyric acid (gaba) is synthesized by polyamine degradation pathway besides gaba shunt. aminoguanidine (ag) is a specific inhibitor of the key enzyme (diamine oxidase, dao) for gaba formation in polyamine degradation pathway. in this study, ag was applied to study the functions of polyamine degradation pathway on growth and gaba accumulation in germinating fava bean under hypo...