Electrical impedance imaging of water distribution in the root zone
Electrical impedance imaging of water distribution in the root zone
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DOI：
10.1088/0957-0233/25/5/055110
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发表时间：
2014-05-01
影响因子：
2.4
通讯作者：
York, T. A.
中科院分区：
文献类型：
--
作者：
Newill, P.;Karadaglic, D.;York, T. A.
该论文描述了一种利用电阻抗的分布式测量来对植物根区内部和周围的水传输进行成像的技术。该技术具有分析地下表型的潜力，例如作物育种计划中的耐旱性状。技术目标是实现自动化、低成本的高通量筛选仪器。最终该技术的目标是现场在线测量。出于演示目的，目前的工作考虑对实验室规模的种植玉米植物的根管进行测量。每个 rhizotron 都配有 60 个呈矩形阵列的电极。为了减少电化学效应，电容耦合非接触式导电 (C4D) 电极的表面具有绝缘层，并且块体材料的电阻是根据光谱考虑推导出来的。测量电极对之间的电阻抗以构建二维图。提出了这种电极的改进电模型，其中包括绝缘层和块体材料的电阻和电抗分量。在含水的平行板测试池上进行的测量证实 C4D 技术能够测量电阻抗。该测试单元已用于探索含水量、压实度和温度对土壤测量的影响。结果证实电阻抗测量对水分含量非常敏感。由于压实高达 0.21 kg cm(-2) 的压力和约 2%/℃ 的温度分数敏感性，观察到阻抗分数变化高达 20%。压实和温度的影响在干燥条件下最为显着。对正在生长的玉米的测量揭示了几周内根管内阻抗的变化。将结果与仅容纳土壤的对照容器进行比较。
The paper describes a technique that is proposed for imaging water transport in and around the root zone of plants using distributed measurements of electrical impedance. The technique has the potential to analyse sub-surface phenotypes, for instance drought tolerance traits in crop breeding programmes. The technical aim is to implement an automated, low cost, instrument for high-throughput screening. Ultimately the technique is targeted at in-field, on-line, measurements. For demonstration purposes the present work considers measurements on laboratory scale rhizotrons housing growing maize plants. Each rhizotron is fitted with 60 electrodes in a rectangular array. To reduce electrochemical effects the capacitively coupled contactless conductivity (C4D) electrodes have an insulating layer on the surface and the resistance of the bulk material is deduced from spectroscopic considerations. Electrical impedance is measured between pairs of electrodes to build up a two-dimensional map. A modified electrical model of such electrodes is proposed which includes the resistive and reactive components of both the insulating layer and the bulk material. Measurements taken on a parallel-plate test cell containing water confirm that the C4D technique is able to measure electrical impedance. The test cell has been used to explore the effects of water content, compaction and temperature on measurements in soil. Results confirm that electrical impedance measurements are very sensitive to moisture content. Impedance fraction changes up to 20% are observed due to compaction up to a pressure of 0.21 kg cm(-2) and a temperature fraction sensitivity of about 2%/degrees C. The effects of compaction and temperature are most significant under dry conditions. Measurements on growing maize reveal the changes in impedance across the rhizotron over a period of several weeks. Results are compared to a control vessel housing only soil.