Putrescine improves salt tolerance of wheat seedlings by regulating ascorbate and glutathione metabolism, photosynthetic performance, and ion homeostasis

To supply more insights into the roles of putrescine (Put) in alleviating salt stress in wheat crops, we explored the effects of Put on ascorbate (ASC) and glutathione metabolism, photosynthetic performance, and ion homeostasis in leaves of salt-stressed wheat seedlings. Our results displayed that salt stress increased the activities of enzymes in ASC and glutathione metabolism, including ascorbate peroxidase, dehydroascorbate reductase, monodehydroascorbate reductase, glutathione reductase, gamma-glutamylcysteine synthetase, and L-galactono-1,4-lactone dehydrogenase, which increased reduced ascorbate (AsA), dehydroascorbate (DHA), reduced glutathione (GSH), oxidised glutathione (GSSG), total ASC and total glutathione contents. Whereas, salt stress induced higher increases in the contents of DHA and GSSG than those of AsA and GSH, which led to reduced AsA/DHA and GSH/GSSG. Meanwhile, salt stress reduced photosynthetic rate (P-n), maximum photochemical efficiency of PSII (F-v/F-m), and the contents of chlorophyll and carotenoids, and destroyed Na+/K+ homeostasis, which further inhibited plant growth. In comparison with salt stress alone, Put strengthened the activities of the above enzymes, which further increased the above metabolites contents, as well as AsA/DHA and GSH/GSSG in leaves of salt-treated seedlings. In this way, Put reduced malondialdehyde content and electrolyte leakage. Besides, Put also increased P-n, F-v/F-m, and above pigments contents, and maintained Na+/K+ homeostasis. Meanwhile, Put increased plant height and biomass of salt-treated seedlings. The present findings clearly implied that Put enhanced salt tolerance of wheat crops by strengthening ASC and glutathione metabolism, photosynthetic performance, and maintaining ion homeostasis in leaves. Therefore, Put can be applied to strengthen the salt tolerance of wheat crops in production and cultivation.