Pulsed 1H NMR in vivo di †erence spectroscopy and germination were combined to elucidate the e †ect 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 and spin-spin relaxation rate is presented. The R 1 R 2 , 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 e †ects, 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.
Abstract— At 293 K the long‐wavelength absorption and emission band of 1.4 μM allophycocyanin is decreased by estriol (Δ1‐3‐5(10)‐estratriene‐3,16α, 17β‐trio!) in the range 0.8‐6.6 μM in the presence of 11% alcohol (vol/vol). The binding of estriol is shown to be of high affinity, 1:1 with allophycocyanin. The free energy of this binding process (ΔG°) is ‐33.6 kJ mol' and single binding site dissociation constant (KD) 1.0 ×10–6M. Estriol at 21 μM effectively quenches the fluorescence of 1.4 M large molecular weight phytochrome in its red absorbing form at 77 K while having little or no effect on the phototransformation difference spectrum at 293 K.
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