FORMATION OF FRACTAL CLUSTERS BY IRREVERSIBLE DIFFUSION-LIMITED BY WATER AGGREGATION IN VIABLE AND DRIED SEEDS

摘要

The gravimetry and 1H-NMR spin-spin relaxation rate (R2) measurements wererncombined to describe the rehydration process in viable or previously dried pea andrntriticale seeds. Equations describing the seed hydration process as well as the 1H-NMRrnspin-echo decay functions in spin-spin experiments can be expressed in a stretchedrnexponential form allowing fractal co-dimension (α) calculations. The α valuesrncalculated from the 1H-NMR and water hydration gravimetric data are the same,rnalthough the time scale of these experiments changes according to 1:107 ratio. Half-timernof seed hydration decreases whereas α co-dimension increases as result of drying. Thernswelling potential related to the osmotic pressure reducing the water uptake to zero,rnshifts from the 1.4 Mpa observed for intact pea seeds to the value of 1.6 Mpa for driedrnpea seeds and from the value 1.3 Mpa for viable to the 1.7 Mpa for dried triticale seeds.rnIn pea seeds, the fractal co-dimension increases with increasing drying time from arnvalue of α≈1.18 to a value of α≈1.35 characteristic for polymer chains percolationrnmechanism.