Diffusion of cell-associated water in ripening barley seeds.

Diffusion rate and restricted diffusion of cell-associated water in ripening barley seeds were examined by NMR microscopy using the pulse gradient spin-echo and the pulse gradient stimulated-echo methods. Changes in the mobility of cell-associated water and properties of cell membranes during ontogeny seed were assessed. Diffusion coefficients for bulk water transfer were high (greater than 0.9 x 10(-5) cm2/s) throughout the growth stages. The highest diffusion coefficient observed was comparable to the self-diffusion coefficient of pure water. Water compartment sizes and the permeability of the cell membranes in the seed were determined by Meerwall and Ferguson's modification of the model of Tanner or by the method of Callaghan et al. The endosperm consisted of large cells and vascular bundle small cells with permeable membranes.