Nuclear Magnetic Resonance in Analysis of Plant Soil Environments

Abstract

This article presents an overview of nuclear magnetic resonance (NMR) methods and their applications in probing the metabolic processes in plants and interaction between plants and soils. The basic principles of both solution‐ and solid‐state NMR are introduced, with an emphasis on useful parameters that can be employed for determining covalent structures and conformations of biomolecules and their environmental derivatives. Both one‐dimensional (1‐D) and two‐dimensional (2‐D) NMR techniques are described, and the advantages of improved resolution and information content for the 2‐D techniques are demonstrated. The substantial improvement in the sensitivity of inverse detection methods for detecting heteronuclei is also shown. Instrumental considerations as well as sample preparation requirements are described for in vivo and in vitro applications and analysis of small and macromolecules. Applications of multinuclear 1‐D and 2‐D NMR in plant metabolism and plant–soil interactions are illustrated. These include in vivo measurements of subcellular compartmentation, determination of metabolite concentrations, enzyme or exchange kinetics, in vitro analysis of plant tissue extracts and root exudates, use of stable isotope tracers for analysis of biochemical pathways, and structural and conformational characterization of natural organic matter (NOM) from soils and sediments. The relative advantages and disadvantages of solution‐ and solid‐state NMR techniques for analysis of plant–soil systems are discussed with examples from characterization of NOM, although 1‐D 13 C solid‐state methods have been of choice due to the polydispersive nature and low aqueous solubility of NOM. However, recent advances in 2‐D solution‐state methods are presented that provide valuable information on structure, conformation, and ligand binding of NOM, which is not practical by solid‐state methods. The limitations of NMR analysis for in vivo, in vitro and NOM are noted, along with a discussion on future prospects for NMR analysis in terms of spectral resolution and detection limits achievable.