Abstract
This chapter describes polyamine synthesis and catabolism in plants, and discusses the role of polyamines in the interactions between plants and their pathogens (fungi, viruses, bacteria, phytoplasmas and viroids). The fungicidal activities of polyamine inhibitors, and the interplay among signalling pathways and molecules (polyamines and nitric oxide, ethylene, jasmonic acid, salicylic acid, and pathogenesis-related proteins) involved in plant disease resistance are described. Advances in the use of transgenic plants in polyamine research are summarized.