Salt stress severely impairs plant growth and productivity. Here, the salinity response modulation by nitrogen nutrition forms was evaluated in two important grass C4 species (sorghum and maize). The crops were grown under nitrate (NO₃⁻) or ammonium (NH₄⁺) nutrition and subjected to salinity with 75 mM NaCl for 7 days. Growth, gas exchange, chlorophyll content, chlorophyll fluorescence, oxidative damage, and antioxidant enzyme activities were evaluated. In salt absence, maize plants displayed low shoot dry mass under NH₄⁺ nutrition compared to NO₃⁻ supply; this injury was intensified by salt exposure. NH₄⁺-grown stressed plants’ elevated sensibility is associated with decreased photosynthetic performance due to photochemical limitations. Although the NH₄⁺-grown stressed maize plants activated superoxide dismutase (SOD) and catalase (CAT) antioxidant enzymes, the mechanisms were inefficient to prevent the oxidative damage, resulting in increased malondialdehyde (MDA) and electrolyte leakage (EL) in the leaves. In sorghum, dry mass was also decreased by salinity, except for NO₃⁻-grown plants, at least in the evaluated time point. Salt-stressed sorghum plants showed unaltered CO₂ assimilation under NH₄⁺ nutrition, a response closely related to maintenance of photosystem II efficiency. Additionally, NH₄⁺-stimulated SOD, guaiacol peroxidase (G-POD), and CAT enzymes’ integrated activities were critical in scavenging reactive oxygen species (ROS) under salinity once the increase in MDA and EL was less prominent than reported for maize plants. Findings clearly evidence that grass species display contrasting responses to salinity and the different N forms, highlighting the high susceptibility of salt-stressed maize plants under NH₄⁺ nutrition and an opposite response for sorghum.

盐胁迫严重损害植物生长和生产力。在这里，在两种重要的草 C4 物种（高粱和玉米）中评估了氮营养形式对盐度响应的调节。作物在硝酸盐 (NO ₃ ^- ) 或铵 (NH ₄ ⁺ ) 营养下生长，并在含 75 mM NaCl 的盐度下生长 7 天。评估了生长、气体交换、叶绿素含量、叶绿素荧光、氧化损伤和抗氧化酶活性。在无盐情况下，与NO ₃ ^-供应相比，玉米植株在NH ₄ ⁺营养下表现出较低的芽干质量；盐暴露加剧了这种伤害。NH ₄ ⁺- 由于光化学限制，生长的受胁迫植物敏感性升高与光合性能下降有关。尽管 NH ₄ ⁺胁迫下生长的玉米植株激活了超氧化物歧化酶 (SOD) 和过氧化氢酶 (CAT) 抗氧化酶，但这些机制无法有效防止氧化损伤，导致叶片中丙二醛 (MDA) 和电解质泄漏 (EL) 增加. 在高粱中，至少在评估的时间点，除NO ₃ ^-生长的植物外，干重也因盐度而降低。盐胁迫的高粱植物在 NH ₄ ⁺下表现出未改变的 CO ₂同化营养，一种与维持光系统 II 效率密切相关的反应。此外，一旦 MDA 和 EL 的增加不如玉米植物报道的那么明显，NH ₄ ⁺刺激的 SOD、愈创木酚过氧化物酶 (G-POD) 和 CAT 酶的综合活性对于在盐度下清除活性氧 (ROS) 至关重要. 研究结果清楚地证明，禾本科植物对盐度和不同的 N 形式表现出截然不同的反应，突出了在 NH ₄ ⁺营养下受盐胁迫的玉米植物的高度敏感性，而对高粱的反应则相反。