Low-field nuclear magnetic resonance for the in vivo study of water content in trees

Abstract

Nuclear magnetic resonance (NMR) and magnetic resonance imaging have long been used to study water content in plants. Approaches have been primarily based on systems using large magnetic fields (~1 T) to obtain NMR signals with good signal-to-noise. This is because the NMR signal scales approximately with the magnetic field strength squared. However, there are also limits to this approach in terms of realistic physiological configuration or those imposed by the size and cost of the magnet. Here we have taken a different approach--keeping the magnetic field low to produce a very light and inexpensive system, suitable for bulk water measurements on trees less than 5 cm in diameter, which could easily be duplicated to measure on many trees or from multiple parts of the same tree. Using this system we have shown sensitivity to water content in trees and their cuttings and observed a diurnal signal variation in tree water content in a greenhouse. We also demonstrate that, with calibration and modeling of the thermal polarization, the system is reliable under significant temperature variation.

In-Vivo NMR Spectroscopy: A Powerful and Complimentary Tool for Understanding Environmental Toxicity

“…While low field NMRs suffer from reduced resolution and sensitivity, their low cost and portability make them ideal for field deployment with often nothing more than a power supply required for monitoring. Some examples, include a mobile NMR lab for leaf phenotyping in the field [ 180 ], a portable sensor for monitoring water and sap flow [ 181 ], a device to detect water content in trees [ 182 , 183 ], fast field cycling NMR in plant leaves [ 184 ], as-well as lipid and metabolites profiling in seeds [ 185 ]. Advancement in technologies such as dynamic nuclear polarization in combination with low field NMR [ 186 ], and zero/ultra-low field NMR with optical detection [ 187 ] offer potential for huge increases in sensitivity that would advance low field NMR into a powerful tool for in-vivo analysis and monitoring.…”

In vivo Observation of Tree Drought Response with Low-Field NMR and Neutron Imaging

“…The nuclei respond by producing an oscillating magnetic field, with frequency f NMR , that can be detected with an AC magnetometer. The experimental data shown in this paper were obtained using a custom NMR system (Figure 1i ) described in detail in Yoder et al ( 2014 ). In brief, the system consists of a set of Helmholtz coils to produce with a magnitude of 860 μ T .…”

“…Permanent magnet systems have also been demonstrated (Windt et al, 2011 ; Jones et al, 2012 ; Windt and Blümler, 2013 ), but their large size and mass creates a challenge for building a network of detectors on many trees, or for working on plants with diameters greater than 1 cm. Here we provide a detailed analysis of the data obtained with a previously reported (Yoder et al, 2014 ) simplified low field NMR system, weighing just a few kilograms. Such low field measurements are made using static magnetic fields below 10 mT, in contrast to fields of several Tesla used in traditional NMR and MRI machines.…”

Study on the Influence of Water–Rock Interaction on the Stability of Schist Slope

“…The distribution of pores will affect the test results and the change of T2 spectrum was used to analyze the change of micro pore structure under different solution conditions. The shorter the relaxation time of transverse axis, the smaller the micro pore diameter, and the position of T2 spectrum peak value was related to the change of sample pore size, while the size of T2 spectrum area was related to the number of sample pores [24,25].…”