Introduction

Identifying mechanisms with potential to increase crop performance under limited water availability is critical to the future of agriculture. Many plant traits (stomatal behavior, specific leaf area, xylem architecture, ROS scavenging, root allocation, and increased osmotic potential) may enable crops to avoid or tolerate water limitation. Additionally, there is evidence that increased nitrogen (N) availability can ameliorate the negative effects of water limitation, although the mechanisms driving this effect are unclear. Here we seek to identify and synthesize the diverse plant physiological mechanisms by which increased N availability may improve plant performance under water limitation. We present four primary plant functional areas in which increased N availability has the potential to offset the negative impacts of water limitation: 1. Belowground resource acquisition, 2. Osmotic adjustment, 3. Photoprotective mechanisms, and 4. Regulation of water and light utilization.

Methods

We synthesized the diverse literature with variable N and water treatments for three important grain crop species: Zea mays, Triticum aestivum, and Oryza sativa. N treatments were standardized to ppm and normalized by soil water holding capacity, background soil N concentrations and number of fertilizer applications.

Results

Ultimately, we conclude that moderate N availability may improve plant yield under water limitation via mechanisms from all four plant functional areas, but high levels of N availability can also be detrimental to plant responses to water limitations.

Discussion

We provide recommendations for specific traits to measure in future field studies, as well as caveats to consider N species, N levels, and timing of N application in such studies.

中文翻译：

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氮的可用性会影响工厂在水分胁迫下的性能吗？性状、机制和全植物效应综述

 介绍

确定在水资源有限的情况下有可能提高作物性能的机制对农业的未来至关重要。许多植物性状（气孔行为、特定叶面积、木质部结构、ROS 清除、根分配和渗透潜力增加）可能使作物能够避免或容忍水分限制。此外，有证据表明，增加氮 （N） 的可用性可以减轻水分限制的负面影响，尽管驱动这种影响的机制尚不清楚。在这里，我们试图识别和综合不同的植物生理机制，通过这些机制，增加氮可用性可能会改善植物在水分限制下的性能。我们提出了四个主要植物功能领域，在这些领域中，增加氮的可用性有可能抵消水限制的负面影响：1. 地下资源获取，2. 渗透调节，3. 光保护机制，以及 4. 水和光利用的调节。

 方法

我们综合了三种重要粮食作物物种的可变氮和水处理的不同文献：玉米、小麦和水稻。氮处理标准化为 ppm，并根据土壤持水能力、背景土壤氮浓度和施肥次数进行标准化。

 结果

最终，我们得出结论，适度的氮有效性可能会通过所有四个植物功能区的机制在水分限制下提高植物产量，但高水平的氮有效性也可能不利于植物对水分限制的反应。

 讨论

我们为未来田间研究中要测量的特定性状提供了建议，并在此类研究中考虑了 N 物种、N 水平和 N 施用时间的注意事项。