Windt Carel W, Blümler Peter
Institute of Bio- and Geosciences, IBG-2: Plant Sciences, Forschungszentrum Jülich, Jülich, Germany
Institute of Physics, University of Mainz, Mainz, Germany.
Tree Physiol. 2015 Apr;35(4):366-75. doi: 10.1093/treephys/tpu105. Epub 2015 Jan 15.
Nuclear magnetic resonance (NMR) and NMR imaging (magnetic resonance imaging) offer the possibility to quantitatively and non-invasively measure the presence and movement of water. Unfortunately, traditional NMR hardware is expensive, poorly suited for plants, and because of its bulk and complexity, not suitable for use in the field. But does it need to be? We here explore how novel, small-scale portable NMR devices can be used as a flow sensor to directly measure xylem sap flow in a poplar tree (Populus nigra L.), or in a dendrometer-like fashion to measure dynamic changes in the absolute water content of fruit or stems. For the latter purpose we monitored the diurnal pattern of growth, expansion and shrinkage in a model fruit (bean pod, Phaseolus vulgaris L.) and in the stem of an oak tree (Quercus robur L.). We compared changes in absolute stem water content, as measured by the NMR sensor, against stem diameter variations as measured by a set of conventional point dendrometers, to test how well the sensitivities of the two methods compare and to investigate how well diurnal changes in trunk absolute water content correlate with the concomitant diurnal variations in stem diameter. Our results confirm the existence of a strong correlation between the two parameters, but also suggest that dynamic changes in oak stem water content could be larger than is apparent on the basis of the stem diameter variation alone.
核磁共振（NMR）和核磁共振成像（磁共振成像）提供了定量且非侵入性地测量水的存在和流动的可能性。不幸的是，传统的核磁共振硬件价格昂贵，不太适合用于植物，并且由于其体积和复杂性，不适合在野外使用。但真的有这个必要吗？我们在此探讨新型小型便携式核磁共振设备如何用作流量传感器，以直接测量杨树（黑杨Populus nigra L.）中的木质部汁液流量，或者以类似测树仪的方式测量果实或茎干绝对含水量的动态变化。为了后一个目的，我们监测了模型果实（菜豆荚，菜豆Phaseolus vulgaris L.）和橡树（夏栎Quercus robur L.）茎干中生长、膨胀和收缩的昼夜模式。我们将核磁共振传感器测量的茎干绝对含水量变化与一组传统点式测树仪测量的茎干直径变化进行比较，以测试这两种方法的灵敏度对比情况，并研究树干绝对含水量的昼夜变化与茎干直径的同步昼夜变化之间的关联程度。我们的结果证实了这两个参数之间存在很强的相关性，但也表明，仅基于茎干直径变化，橡树茎干含水量的动态变化可能比表面上看起来的要大。
