In situ studies of plant seeds using 13 C or 1 H MAS NMR and 1H PFG NMR approaches

Abstract

NMR can be used for in situ studies of lipidic components, mainly triacylglycerols (TAG), in mature seeds. Lipids can be one of the most abundant constituents of seeds in oleaginous crops. The inputs of high-resolution solidstate 1 H or 13 C NMR and pulsed field gradient 1H NMR (PFG NMR) are presented in this chapter. By combining single pulse excitation (SP) and crosspolarization (CP) experiments, both liquid and solid domains of plant seeds can be characterized and the assignments of the corresponding 13 C and 1 H can be performed. As TAG are confined in oil bodies (OBs), analysis of their diffusion properties, determined with PFG NMR, is a well-suited experimental approach to determine OB sizes. In fact, at long diffusion time, TAG mean squared displacement is limited by the OB size. In order to access the OB size distribution, strong intensities of magnetic field gradients are generally required. However, using a standard liquid-phase NMR probe equipped with a weak-intensity gradient coil, the mean size of OBs can be determined. OB diameters obtained by PFG NMR were fully consistent with previously published values obtained by microscopy techniques.