Drought and atmospheric nitrogen deposition (AND) become increasingly serious in recent decades owing to the progressively rising anthropogenic activities. Thus, it is significant to assess the effects of combined drought and AND on plant morphological and physiological performance (MorPhyPer) to better elucidate the mechanisms that drive the successful plant life-history strategies under the combined drought and AND. The objective of this study is to evaluate the combined drought [imitated by polyethylene glycol-6000 (PEG 6000) solution] with different degrees and AND [a mixed N with a 1: 1: 1 ratio of NH 4 –N: NO 3 –N: CO(NH 2 ) 2 –N] with different concentrations on MorPhyPer of wheat ( Triticum aestivum L.) via the garden-pot cultivation under the condition with natural light for nearly sixty days. Results showed that drought dramatically reduced MorPhyPer of wheat. This phenomenon may be attributed to the gradually enhanced osmotic pressure generated by the dehydrated condition, the enhanced degrees of reactive oxygen species, the raised level of plant cell cytoplasm membrane peroxidation, and/or the downgraded plant enzymatic defensive ability. AND notably improved MorPhyPer of wheat mostly owing to the relieved N deficiencies. The combined drought and AND antagonistically affect plant supporting ability, leaf photosynthetic area, and belowground growing competitiveness of wheat. The reason may be due to the increased belowground moisture content under the combined drought and AND which can improve the efficiency and capacity of nutrients absorption (mainly absorb more N nutrients) by root and transport to the aboveground portion and subsequently raise the level of drought resistance. The reason may be also attributed to the enhanced leaf photosynthetic area which can capture more sunlight and increase the tolerance to the adverse environment. Accordingly, AND notably alleviated the unfavorable effects of drought on MorPhyPer of wheat basically.

中文翻译：

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大气氮沉降缓解干旱对小麦生长的不利影响

近几十年来，由于人类活动的不断增加，干旱和大气氮沉降（AND）变得越来越严重。因此，评估干旱和AND联合对植物形态和生理性能（MorPhyPer）的影响，以更好地阐明在干旱和AND联合下驱动植物生命史策略成功的机制具有重要意义。本研究的目的是评估不同程度的组合干旱 [由聚乙二醇-6000 (PEG 6000) 溶液模拟] 和 [混合 N 与 1:1:1 的 NH 4 –N: NO 3 – N: CO(NH 2 ) 2 –N] 在自然光条件下花盆栽培近 60 天对小麦 (Triticum aestivum L.) 的 MorPhyPer 的不同浓度。结果表明，干旱显着降低了小麦的 MorPhyPer。这种现象可能是由于脱水条件下产生的渗透压逐渐增强、活性氧水平增强、植物细胞质膜过氧化水平升高和/或植物酶防御能力下降所致。并且显着改善了小麦的 MorPhyPer，这主要是由于减轻了 N 缺乏症。干旱和AND的联合对抗性影响小麦的植株支撑能力、叶片光合面积和地下生长竞争力。其原因可能是干旱和AND联合作用下地下含水量增加，可以提高根系吸收养分（主要是吸收更多的氮养分）并输送到地上部分的效率和能力，进而提高抗旱水平。 . 究其原因，也可能是由于叶片光合面积增强，可以捕获更多的阳光，增加对不利环境的耐受性。因此，AND显着缓解了干旱对小麦MorPhyPer的不利影响。