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Jülich, Germany

Dadshani S.,University of Bonn | Kurakin A.,EMISENS GmbH | Amanov S.,University of Bonn | Hein B.,University of Bonn | And 8 more authors.
Plant Methods | Year: 2015

The water status in plant leaves is a good indicator for the water status in the whole plant revealing stress if the water supply is reduced. The analysis of dynamic aspects of water availability in plant tissues provides useful information for the understanding of the mechanistic basis of drought stress tolerance, which may lead to improved plant breeding and management practices. The determination of the water content in plant tissues during plant development has been a challenge and is currently feasible based on destructive analysis only. We present here the application of a non-invasive quantitative method to determine the volumetric water content of leaves and the ionic conductivity of the leaf juice from non-invasive microwave measurements at two different frequencies by one sensor device. A semi-open microwave cavity loaded with a ceramic dielectric resonator and a metallic lumped-element capacitor- and inductor structure was employed for non-invasive microwave measurements at 150 MHz and 2.4 Gigahertz on potato, maize, canola and wheat leaves. Three leaves detached from each plant were chosen, representing three developmental stages being representative for tissue of various age. Clear correlations between the leaf- induced resonance frequency shifts and changes of the inverse resonator quality factor at 2.4 GHz to the gravimetrically determined drying status of the leaves were found. Moreover, the ionic conductivity of Maize leaves, as determined from the ratio of the inverse quality factor and frequency shift at 150 MHz by use of cavity perturbation theory, was found to be in good agreement with direct measurements on plant juice. In conjunction with a compact battery- powered circuit board- microwave electronic module and a user-friendly software interface, this method enables rapid in-vivo water amount assessment of plants by a handheld device for potential use in the field. © 2015 Dadshani et al.; licensee BioMed Central. Source

Klein N.,Imperial College London | Klein N.,EMISENS GmbH | Krause H.-J.,Julich Research Center | Vitusevich S.,Julich Research Center | And 6 more authors.
IEEE MTT-S International Microwave Symposium Digest | Year: 2011

An open metal cavity loaded with a ceramic dielectric resonator and a lumped inductor - capacitor structure allows for simultaneous excitation of the TE01δ dielectric resonator mode at 2 GHz and a lumped element mode at 100 MHz. The measured quality factors are about 7,000 and 400, respectively. Both modes exhibit strongly overlapping evanescent fields above the aperture outside the cavity. These fields can be used for dielectric and conductivity measurements on liquids stored in non-metallic bottles. The simultaneous use of both modes enables liquid category identification within one second. This method has been successfully applied for bottle scanning in checkpoints. © 2011 IEEE. Source

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