Ontogenetic changes of water states and structural organization in growing kidney beans: parameter-imaging based on the diffusion measurements.
Physical states of cell-associated water in growing kidney beans was studied by NMR microscopy. 1H-NMR images indicated the changes of water amount in the individual tissues. The seed gradually reduced water and water in the tissues of the pod varied according to growth stages. Images that reflect diffusive motion provide different contrast from that of the proton images; signal intensity was maintained in the tissues containing small amounts of water and showing weak signal on the proton images. These images are related to the activity of metabolism and physiological functions. The parameter-images provided the structural information about cellular matrix, the barrier spacing of water compartments and the reduced permeability of cell-membranes surrounding the compartment, were created based on the restricted diffusion of cell-associated water. The properties of the water compartment changed with the stages of growth in individual tissues of the fruits. Two types of water compartments were detected; one had approximately 65 microm spacing and constant permeability (20-25%) throughout the stages of growth, and another had the smaller and variable spacing (approximately 35 microm), and a lower permeability. The former belongs to the seed and the mesocarp, the exocarp and the epidermis of the pod. While the latter characterizes the properties of the primary tissue in the pod, the endocarp, which increased with development of the pod then showed reduction with the decrease of water in the pod with the fruit growth.