Effect of electric field on physical states of cell-associated water in germinating morning glory seeds observed by H-1-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 germina ting seeds of both control and exposed groups were examined using H-1-NMR s pectroscopy and NMR microscopy. Three water fractions were observed which w ere 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 intracell ular water transport rate was 2.3 x 10(-5) cm(2)/s. The treatment with elec tric 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 untrea ted seeds (3.9 g HzO/dry wt.), the treated seeds held more water in a condi tion 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 d uring the imbibition process. This set of events led to excessive swelling of stored macromolecules, resulting in the disruption of membrane systems a nd irregular organization of tissue structures. (C) 1999 Elsevier Science B .V. All rights reserved.