Effective role of putrescene in mitigating harmful effects of salinity on rapeseed seedlings via modulating morpho-physiochemical and molecular processes

Understanding tolerance mechanisms and categorizing reliable physiochemical indicators related to their mechanisms is important for enhancing rapeseed tolerance and sustainable agricultural development. Putrescine (Put), one of the important polyamines, plays a promising role in promoting the synthesis of bioactive compounds related to plant development, especially under stress conditions. Herein, the potential role of Put in alleviating salt stress in rapeseed has been thoroughly investigated via priming application with different concentrations (0.1, 0.3, 0.5, 0.7, and 1 mM). Seed germination-related parameters and hormone-related genes were studied during seed imbibition under 150 mM of NaCl. Additionally, morpho-physiochemical characteristics, ionic content, and ion exchange-related genes were investigated in the shoots and roots of 7-day-old seedlings under salinity stress. Our results showed that Put-priming improved germination parameters by regulating seed germination and hormone-related genes under salinity stress, especially at 0.3 and 0.5 mM Put, compared with unprimed and hydroprimed (HP) seeds. Besides, it significantly enhanced seedling growth by preventing the degradation of photosynthetic pigments and modulating the proline and soluble solute accumulation in shoots and roots. Moreover, MDA, H 2 O 2 , and O 2 contents decreased with Put-priming, especially at 0.5 mM, indicating the significant role of Put in ROS scavenging and inhibiting lipid peroxidation upon stress. Put-priming alleviated salt-induced oxidative stress by enhancing the structure and function of the enzymatic and non-enzymatic antioxidative systems, which protect the integrity of cellular membranes in seedlings under stress conditions. Our study observed increased Na + and decreased K + contents under salt treatments versus control (Ctrl), whereas Put treatments not only reduced Na + but also increased K + accumulation, lowering the Na + /K + ratio, especially at 0.3 and 0.5 mM Put versus unprimed and HP seedlings. Put-priming showed strikingly stronger effects on intracellular Na + and K + homeostasis by regulating ion exchange-related genes, which upregulated the gene expression of BnH + -ATPase , BnNHX6 , BnSOS1 , BnSKOR , BnHKT1, and BnHKT8 that modulated Na + influx and K + efflux under salinity stress. Our results provide an integrative understanding and scientific basis for the exogenous application of Put as a promising method for improving salt tolerance in rapeseed seedlings at morpho-physiochemical and molecular levels, which provides a convenient, fast, and environmentally friendly strategy to help crops adapt to be used for cultivation in saline soil. • Put regulating germination and hormone-related genes upon salt stress conditions. • Put enhances seedling growth, preserves photosynthetic pigments, and reduces oxidative stress. • Put-priming reduced salt-induced ion toxicity via osmolyte and antioxidant systems. • Put-priming modulates intracellular Na + and K + homeostasis by upregulating genes of ion exchange. • Put is a promising material in ameliorating rapeseed growth under salt stress.