Gibberellin and spermidine synergistically regulate polyamine metabolism during the development of Rhododendron flowers

Polyamines (PAs) are involved in various developmental processes, especially plant flowering. Their significant influences have been established; however, the exact mechanism by which PAs regulate flowering remains unclear. To explore PA metabolism flowering, gibberellic acid (GA3, 0~2400 mg L?1) and spermidine (Spd, 0~1 mM) were applied alone or combination during early stage of flower bud formation Rhododendron simsii. The application GA3 advanced initial while that Spd delayed Interestingly, 2 days. Furthermore, from 1 to 2, endogenous levels soluble conjugated insoluble bound fractions key enzymes (e.g., diamine oxidase, arginine decarboxylase, ornithine decarboxylase S-adenosylmethionine decarboxylase) increased, level oxidase decreased. These findings revealed exogenous delay senescence improving biosynthesis preventing degradation. Moreover, enhanced GA3, conversion free forms senescence. Overall, our reveal a potential positive feedback higher contents combined effects synergistically enhancing converting forms, thus reducing degradation