Morphological, physiological and biochemical changes and effects of polyamines on regulation of Anoectochilus roxburghii during flowering period

Objective Anoectochilus roxburghii is a valuable medicinal and ornamental plant. The aim of this study is to investigate the morphological and biochemical responses during the flower development stages of A. roxburghii , and to assess the effects of exogenous polyamines (PAs) on bud differentiation and metabolism, thereby providing a theoretical basis for understanding the flowering form and physiology of A. roxburghii . Methods In this study, morphological and biochemical responses in flower development stages of A. roxburghii were investigated using paraffin sections and stereomicroscope. A. roxburghii was divided into five periods, including vegetative growth period, flower bud period, flowering period, late flowering period and fruiting period. During the flowering phase, specific biochemical parameters were measured, including soluble sugar content, superoxide dismutase (SOD) activity, soluble protein content, peroxidase (POD) activity, and catalase (CAT) activity. These measurements were conducted to understand the biochemical changes occurring within A. roxburghii during its flowering process. Furthermore, the effects of PAs on bud differentiation were examined. Additionally, the activities of S-adenosylmethionine decarboxylase (SAMDC) and polyamine oxidase (PAO), as well as the content of polyphenols, polysaccharides, and flavonoids in A. roxburghii , were measured after PA treatment to evaluate the metabolic changes induced by exogenous PAs. Results During the flowering phase of A. roxburghii , soluble sugar content and SOD activity were steadily declining. Soluble protein content was initially increasing and then reducing, and POD and CAT activities showed opposite pattern. In addition, the effects of exogenous PAs on bud differentiation were investigated. Results showed that 3 mmol/L putrescine or 0.3 mmol/L spermidine significantly promoted the bud differentiation of A. roxburghii and advanced the flowering. The activities of SAMDC, PAO, and the content of polyphenols, polysaccharides and flavonoids in A. roxburghii significantly increased after PA treatment, demonstrating that exogenous PA can accelerate metabolism and improved the active ingredients content. Conclusion The flower development of A. roxburghii was divided into five stages, with significant changes in soluble sugar, protein, POD, SOD, CAT, MDA, and PRO levels. Exogenous putrescine and spermidine enhanced bud differentiation and accelerated flowering, increasing SAMDC and PAO activities, suggesting accelerated PA metabolism. PAs also improved active component content. These findings provide a theoretical basis for studying flower morphology and PA-induced flowering regulation of A. roxburghii .