Department of Agronomy and Plant Genetics, University of Minnesota, St Paul, MN, 55108, USA.
Department of Ecology, Evolution, and Behavior, University of Minnesota, St Paul, MN, 55108, USA.
New Phytol. 2023 Jul;239(1):54-65. doi: 10.1111/nph.18929. Epub 2023 Apr 25.
Atmospheric vapor-pressure deficit (VPD) is increasing in many regions and has a large impact on plant productivity. A VPD increase leads to raising transpiration rate (TR) and soil-water demand, risking productivity penalties. Like water, nitrogen is critical to productivity, but the effect of VPD on legume nitrogen fixation is undocumented. To address this, we developed a portable system for quantifying nitrogen fixation noninvasively and at a high temporal resolution by tracking the rate of hydrogen gas evolution by root nodules. Combining field and controlled-environment experiments where we measured leaf gas exchange and H production by nodules, we confirmed the ability of the system to track nitrogen fixation dynamics. Raising VPD from 0.5 to 3 kPa within c. 2.5 h under well-watered conditions increased nitrogen fixation by up to 25% in addition to TR, consistent with the hypothesis that raising VPD in that range might have alleviated nitrogenase feedback inhibition. Genotypic differences were found in this response, indicating a potential for breeding. Our study provides evidence for an important environmental effect on nitrogen fixation that is not taken into account in current crop and vegetation models, pointing to untapped avenues for better understanding climate change effects on legumes and nitrogen cycling.
大气蒸气压亏缺 (VPD) 在许多地区都在增加，对植物生产力有很大影响。VPD 的增加会导致蒸腾速率 (TR) 和土壤水分需求的增加，从而有可能导致生产力下降。与水一样，氮对生产力至关重要，但 VPD 对豆科植物固氮的影响尚未有记录。为了解决这个问题，我们开发了一种便携式系统，可以通过跟踪根瘤产生的氢气的速率来非侵入性地、以高时间分辨率定量测量固氮。我们结合了田间和控制环境实验，在这些实验中我们测量了叶片气体交换和根瘤产生的 H，证实了该系统能够跟踪固氮动力学。在充分供水条件下，将 VPD 在大约 2.5 小时内从 0.5 升高到 3 kPa，除了 TR 之外，还增加了高达 25%的固氮，这与提高该范围内的 VPD 可能缓解氮酶反馈抑制的假设一致。在这种反应中发现了基因型差异，表明有进行选育的潜力。我们的研究为氮固定的一个重要环境效应提供了证据，而目前的作物和植被模型并未考虑到这一点，这为更好地理解气候变化对豆科植物和氮循环的影响指明了未开发的途径。
