Multi-frequency electrical impedance tomography as a non-invasive tool to characterize and monitor crop root systems
Multi-frequency electrical impedance tomography as a non-invasive tool to characterize and monitor crop root systems
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DOI：
10.5194/bg-14-921-2017
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发表时间：
2017-02-28
期刊：
影响因子：
4.9
通讯作者：
Kemna, Andreas
中科院分区：
文献类型：
--
作者：
Weigand, Maximilian;Kemna, Andreas
更好地了解根-土相互作用和相关过程对于作物育种和管理取得进展至关重要，这促使需要高分辨率和非破坏性的表征方法。迄今为止，这些方法仍然缺乏或受到技术限制，特别是在田间对根生长和功能的表征和监测。在这方面，一种有前途的技术是电阻抗断层成像（EIT），它利用低频（< 1 kHz）的导电和极化特性的成像框架。众所周知，由于在细胞膜上形成的双电层，细胞和细胞簇在交变电流场中表现出电极化响应。这种双层与膜的电表面性质直接相关，而电表面性质又受到营养物动力学（膜两侧的通量和浓度）的影响。因此，可以认为根系的电极化特性与根系中离子的吸收和转运过程有着内在的联系。我们在此提出宽带（mHz至数百Hz）多频率EIT作为用于监测和生理的非侵入性方法学途径，即，作物根系的功能和特性。该方法将成像方法的空间分辨率能力与电阻抗谱的诊断潜力相结合。多频EIT表征和监测作物根系的能力进行了研究，在一个实验室实验中，在一个充满水的根区，也就是说，在营养缺乏的环境中监测的油料作物的根系。我们发现了一个低频极化响应的根系，这使得成功地描绘其空间延伸。随着胁迫条件下根系的生理衰退，整个极化响应的幅度沿着减小。光谱极化参数，来自基于像素的德拜分解分析的多频成像结果，揭示了系统的变化，在空间和光谱的根系电响应。特别是，量化的平均弛豫时间（10毫秒的顺序）表示的长度尺度上的极化过程发生在根系的变化，作为一个响应的长期诱导应力的情况。我们的研究结果表明，宽带EIT是一种有能力的，非侵入性的方法来成像根系的扩展，以及监测与根的生理过程的变化。鉴于其在实验室和现场规模的适用性，我们的研究结果表明一个巨大的潜力的根系的结构和功能成像的方法，用于各种应用。这特别适用于现场规模，其中非常需要相应的方法，但迄今为止还缺乏。
A better understanding of root-soil interactions and associated processes is essential in achieving progress in crop breeding and management, prompting the need for high-resolution and non-destructive characterization methods. To date, such methods are still lacking or restricted by technical constraints, in particular the charactization and monitoring of root growth and function in the field. A promising technique in this respect is electrical impedance tomography (EIT), which utilizes low-frequency (< 1 kHz)-electrical conduction-and polarization properties in an imaging framework. It is well established that cells and cell clusters exhibit an electrical polarization response in alternating electric-current fields due to electrical double layers which form at cell membranes. This double layer is directly related to the electrical surface properties of the membrane, which in turn are influenced by nutrient dynamics (fluxes and concentrations on both sides of the membranes). Therefore, it can be assumed that the electrical polarization properties of roots are inherently related to ion uptake and translocation processes in the root systems. We hereby propose broadband (mHz to hundreds of Hz) multi-frequency EIT as a non-invasive methodological approach for the monitoring and physiological, i.e., functional, characterization of crop root systems. The approach combines the spatial-resolution capability of an imaging method with the diagnostic potential of electrical-impedance spectroscopy. The capability of multi-frequency EIT to characterize and monitor crop root systems was investigated in a rhizotron laboratory experiment, in which the root system of oilseed plants was monitored in a water-filled rhizotron, that is, in a nutrient-deprived environment. We found a low-frequency polarization response of the root system, which enabled the successful delineation of its spatial extension. The magnitude of the overall polarization response decreased along with the physiological decay of the root system due to the stress situation. Spectral polarization parameters, as derived from a pixel-based Debye decomposition analysis of the multi-frequency imaging results, reveal systematic changes in the spatial and spectral electrical response of the root system. In particular, quantified mean relaxation times (of the order of 10 ms) indicate changes in the length scales on which the polarization processes took place in the root system, as a response to the prolonged induced stress situation. Our results demonstrate that broadband EIT is a capable, non-invasive method to image root system extension as well as to monitor changes associated with the root physiological processes. Given its applicability on both laboratory and field scales, our results suggest an enormous potential of the method for the structural and functional imaging of root systems for various applications. This particularly holds for the field scale, where corresponding methods are highly desired but to date are lacking.