Drought and salinity are the most serious environmental factors affecting crop productivity worldwide; hence, it is important to select and develop both salt- and drought-tolerant crops. The perennial smooth cordgrass Spartina alterniflora Loisel is unusual in that it is highly salt-tolerant and seems to prefer ammonium (NH4 + ) over nitrate (NO3 - ) as an inorganic N source. In this study, we determined whether Spartina's unique preference for NH4 + enhances performance under salt and drought stress. Greenhouse experiments were conducted to compare the interactive effects of N source, salinity, and low water availability on plant performance (growth and antioxidant metabolism). Drought significantly reduced growth and photosynthetic activity in S. alterniflora, more so with NH4 + than NO3 - ; in contrast, NH4 + enhanced growth under high salinity. The increased tolerance of S. alterniflora to salt stress in the presence of NH4 + was linked to a high level of antioxidant enzyme activity, combined with low MDA content, EL, and H2 O2 production. In contrast, drought stress negated the growth advantages for S. alterniflora exposed to salt stress in the presence of NH4 + . The susceptibility of S. alterniflora to drought was partly due to reduced antioxidant enzyme activities, thereby reducing the defense against the oxidative damages induced by osmotic stress. In conclusion, in contrast to salt stress, drought stress negates the beneficial effects of ammonium as an N source in the C4 plant Spartina alterniflora.

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干旱和盐度：比较它们对偏好铵的物种互花米草的影响

干旱和盐度是影响全球作物生产力的最严重的环境因素；因此，选择和开发耐盐和耐旱作物非常重要。多年生光滑的禾本科 Spartina alterniflora Loisel 是不寻常的，因为它具有高度的耐盐性，并且似乎更喜欢铵 (NH4 + ) 而不是硝酸盐 (NO3 - ) 作为无机氮源。在这项研究中，我们确定了 Spartina 对 NH4 + 的独特偏好是否会提高盐和干旱胁迫下的性能。进行温室试验以比较氮源、盐度和低可用水量对植物性能（生长和抗氧化代谢）的交互作用。干旱显着降低了互花米草的生长和光合活性，NH4 + 比 NO3 - 更是如此；相比之下，NH4 + 在高盐度下促进生长。在 NH4 + 存在下，互花米草对盐胁迫的耐受性增加与高水平的抗氧化酶活性以及低 MDA 含量、EL 和 H2 O2 产量有关。相比之下，干旱胁迫使互花米草在 NH4 + 存在下暴露于盐胁迫下的生长优势无效。S. alterniflora 对干旱的敏感性部分是由于抗氧化酶活性降低，从而降低了对渗透胁迫诱导的氧化损伤的防御。总之，与盐胁迫相反，干旱胁迫否定了铵作为 C4 植物互花米草中氮源的有益作用。在 NH4 + 存在下，互花米草对盐胁迫的影响与高水平的抗氧化酶活性有关，并与低 MDA 含量、EL 和 H2 O2 产量相结合。相比之下，干旱胁迫使互花米草在 NH4 + 存在下暴露于盐胁迫下的生长优势无效。S. alterniflora 对干旱的敏感性部分是由于抗氧化酶活性降低，从而降低了对渗透胁迫诱导的氧化损伤的防御。总之，与盐胁迫相反，干旱胁迫否定了铵作为 C4 植物互花米草中氮源的有益作用。在 NH4 + 存在下，互花米草对盐胁迫的影响与高水平的抗氧化酶活性有关，并与低 MDA 含量、EL 和 H2 O2 产量相结合。相比之下，干旱胁迫使互花米草在 NH4 + 存在下暴露于盐胁迫下的生长优势无效。S. alterniflora 对干旱的敏感性部分是由于抗氧化酶活性降低，从而降低了对渗透胁迫诱导的氧化损伤的防御。总之，与盐胁迫相反，干旱胁迫否定了铵作为 C4 植物互花米草中氮源的有益作用。互花米草对干旱的影响部分是由于抗氧化酶活性降低，从而降低了对渗透胁迫诱导的氧化损伤的防御。总之，与盐胁迫相反，干旱胁迫否定了铵作为 C4 植物互花米草中氮源的有益作用。互花米草对干旱的影响部分是由于抗氧化酶活性降低，从而降低了对渗透胁迫诱导的氧化损伤的防御。总之，与盐胁迫相反，干旱胁迫否定了铵作为 C4 植物互花米草中氮源的有益作用。