NMR methods have a unique capability for the studying of water relations in biological systems by virtue of their being noninvasive and nondestructive.
We will show here the potential use of the proton NMR technique for studying all aspects of water relations of plants including: (1) water exchange across the membranes of both single cells (algae) and cells within tissues, (2) radial water transport (short distance) and controlling steps of water transport in root tissue, and (3) xylem (long distance) transport of water in plants.
In addition we will demonstrate the potential of magnetic resonance imaging (MRI) in studying different aspects of water relations of plants by observing water as seen in a MR image of a cross section through plant tissue (stem or root) obtained no ninvasively.
The basic discoveries of nuclear induction made in 1946 laid down the fundamentals of the nuclear magnetic resonance (NMR technique, which has had an explosive development, with application in all branches of physics, chemistry and biology. The sophisticated 13C and 31P NMR spectroscopy has been successfully applied to studies of metabolism and transport processes in plants (Loughman & Ratcliffe, 1984; Roberts, 1987).
Since our interest here is in water transport in plants we shall consider those NMR techniques which can measure resonance and relaxation of hydrogen nuclei, i.e. protons, in water molecules, and will also show that the proton NMR signal of water in plants is dependent on the state of water in the tissue and on the motion of the fluid within the NMR probe.