Seven-day-old maize seedlings were subjected to NaCl (150 mM) without or with the presence of equimolar concentrations of urea, potassium nitrate or ammonium sulfate (at 60 kg N ha⁻¹) for the subsequent 15 days. The results show that NaCl significantly decreased photosynthetic activity parameters (Hill reaction, Pn, Ci and Gs), shoot fresh and dry weights, chlorophylls, protein, GSH and AsA. The activities of ALA-D, Rubisco, PEP-C, MDH, PPDK, SOD, CAT and APX were significantly inhibited. On the contrary, NaCl significantly elevated MDA, O^∙−₂, H₂O₂, soluble sugars and proline. The application of the nitrogenous sources mostly ameliorated the photosynthetic activity synchronous with counterbalancing the decreases in growth, protein and pigments. The activities of ALA-D, Rubisco, PEP-C, MDH and PPDK enhanced remarkably with N applied under salinity. Furthermore, enhancements were detected in GSH and AsA contents and SOD, CAT and APX activities, which decreased free radicals, soluble sugars and proline. These effects reveal that maize was vulnerable to NaCl stress; however, N overcame the stress status and ameliorated the plant tolerance to salinity concomitant with repairing photosynthetic activity and maintaining higher antioxidants and ROS homeostasis; urea seemed to be the most efficient. Taken together, these findings conclude that N enhanced the capability of maize to tolerate NaCl via protecting photosynthetic apparatus for normal photochemical functioning and improving antioxidants and ROS homeostasis as effective salt tolerance mechanisms.

在随后的15天中，将7天大的玉米幼苗在无或存在等摩尔浓度的尿素，硝酸钾或硫酸铵（60 kg N ha ^-1）下进行NaCl（150 mM）处理。结果表明，NaCl显着降低了光合活性参数（Hill反应，Pn，Ci和Gs），鲜重和干重，叶绿素，蛋白质，GSH和AsA。显着抑制了ALA-D，Rubisco，PEP-C，MDH，PPDK，SOD，CAT和APX的活性。相反，NaCl显着提高了MDA，O ^∙− ₂，H ₂ O ₂，可溶性糖和脯氨酸。氮源的施用主要与平衡生长，蛋白质和色素的减少同时改善了光合作用。在盐度下施氮可显着提高ALA-D，Rubisco，PEP-C，MDH和PPDK的活性。此外，检测到GSH和AsA含量以及SOD，CAT和APX活性增强，从而减少了自由基，可溶性糖和脯氨酸。这些影响表明玉米很容易受到NaCl胁迫的影响。然而，N克服了胁迫状态，并改善了植物对盐分的耐受性，同时修复了光合作用，维持了较高的抗氧化剂和ROS稳态。尿素似乎是最有效的。在一起