Effect of electric field on physical states of cell-associated water in germinating morning glory seeds observed by 1H-NMR

Morning glory seeds in dry conditions (0.099 g H2O/dry wt.) were exposed to electric fields and germinated. The physical state of water in the germinating seeds of both control and exposed groups were examined using H-1-NMR spectroscopy and NMR microscopy. Three water fractions were observed which were characterized by different relaxation times (T-1) and chemical shifts. The average region containing long T-1 fractions was approximately 50 mu m in diameter and consisted of half-permeable barriers. The maximum intracellular water transport rate was 2.3 x 10(-5) cm(2)/s. The treatment with electric field (500 kV/m for 60 min) increased the fraction with the shortest T-1 and decreased that with the longest T-1. Because the total water content in the treated seeds (3.4 g HzO/dry wt.) was similar to that in the untreated seeds (3.9 g HzO/dry wt.), the treated seeds held more water in a condition in restricted motion than the untreated seeds. It is thought that the membrane systems were affected by the electric polarization which led to an unusual accumulation of water and the hydration of stored macromolecules during the imbibition process. This set of events led to excessive swelling of stored macromolecules, resulting in the disruption of membrane systems and irregular organization of tissue structures. (C) 1999 Elsevier Science B.V. All rights reserved.