title: 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.
authors.affiliation: Inorganic, Isotope and Actinide Chemistry, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA.
authors.forename: Jacob
authors.initials: J
authors.lastname: Yoder
authors.affiliation: Applied Modern Physics, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA.
authors.forename: Michael W
authors.initials: MW
authors.lastname: Malone
authors.affiliation: Applied Modern Physics, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA.
authors.forename: Michelle A
authors.initials: MA
authors.lastname: Espy
authors.affiliation: Earth Systems Observations, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA.
authors.forename: Sanna
authors.initials: S
authors.lastname: Sevanto
mesh_terms: D004780:Environment, Controlled; D009682:Magnetic Resonance Spectroscopy / Q000295:instrumentation / Q000379:methods*; D014197:Trees / Q000737:chemistry*; D014867:Water / Q000032:analysis* / Q000737:chemistry*
chemical_list: D014867:Water