Impact of chemical stimuli and temperature on water transport and mobility in germinating rape seeds by pulsed1H NMR spectroscopy

Abstract

Pulsed 1H NMR in vivo difference spectroscopy and germination were combined to elucidate the effect of exogenously applied estriol or ethanol on water retention in fully hydrated rape seeds. The presence of estriol or ethanol in the imbibition medium resulted in a reduction of the photoreversible phytochrome. An approach to the assessment of cell membrane permeability related to the intracellular water exchange rate, using the bi‐exponential feature in the water proton spin–lattice relaxation rate R1 and spin–spin relaxation rate R2, is presented. The intracellular water exchange rate increases approximately two‐ and three‐fold in seeds pre‐treated with estriol or ethanol solution in comparison with water imbibed seeds. The activation energy for the germination rate was 61±6, 42±4 and 37±4 kJ mol‐1 and the transition temperature was 281±2, 286±2 and 284±2 K for seeds imbibed with water, estriol and ethanol solution, respectively. The temperature dependence of the intracellular water exchange rate showed comparable values of activation energy and transition temperatures. All the results support the hypothesis that the two effects, thermal activation and increase in the seed cell membrane permeability, combine during water transport into the cell and result in the germination of rape seeds imbibed with estriol or ethanol solution. © 1997 John Wiley & Sons, Ltd.