Previous studies reported an effect of water deficit on crop nitrogen (N) demand but the statistical significance of this effect is unclear and the physiological mechanism explaining this effect remains poorly understood. The specific aims of this review are (i) assess whether the parameters of the N dilution curve are significantly influenced by the level of water availability and (ii) provide a synthesis of the plausible physiological mechanisms involved on changes in N dilution. To address the first goal, several datasets assessing the effects of water availability on N status of maize (Zea mays L.), wheat (Triticum aestivum L.), and tall fescue (Lolium arundinaceum (Schreb.) Darbysh.) were combined and then used to fit N dilution curves with a Bayesian statistical approach. Concerning the second objective, we investigate two possible mechanisms, namely a modification in water soluble carbohydrates (WSCs) and an effect on plant architecture and morphology impacting the allometry between structural and metabolic compartment. Our re-analysis of published data for tall fescue, wheat, and maize reveals no conclusive evidence supporting an effect of water availability effect on the N dilution curve. In addition, we show that WSCs accumulation under water deficit condition is unlikely to be accompanied by N-rich soluble compounds, and that a reduction of water availability has limited effect on the allometry of plant mass allocation. Lastly, our conclusion provides new insights on the use of a common critical N dilution curve (one model across water levels) for estimating the crop N status where both water (under no extreme deficiency) and N stresses are operating in order to separate direct effect of water availability from its indirect effect on crop N nutrition status.

以前的研究报告了水分亏缺对作物氮 (N) 需求的影响，但这种影响的统计意义尚不清楚，解释这种影响的生理机制仍然知之甚少。本次审查的具体目标是 (i) 评估 N 稀释曲线的参数是否受可用水量水平的显着影响，以及 (ii) 提供与 N 稀释变化相关的合理生理机制的综合。为了实现第一个目标，几个数据集评估了水的可用性对玉米 ( Zea mays L.)、小麦 ( Triticum aestivum L.) 和高羊茅 ( Lolium arundinaceum(Schreb.) Darbysh.) 被合并，然后用贝叶斯统计方法拟合 N 个稀释曲线。关于第二个目标，我们研究了两种可能的机制，即水溶性碳水化合物 (WSC) 的修饰以及对影响结构和代谢区室之间异速生长的植物结构和形态的影响。我们对已发表的高羊茅、小麦和玉米数据的重新分析表明，没有确凿的证据支持水分利用率对 N 稀释曲线的影响。此外，我们表明缺水条件下的 WSCs 积累不太可能伴随着富含 N 的可溶性化合物，并且水可用性的减少对植物质量分配的异速生长影响有限。最后，