Dielectric Relaxation of Water and Water-Plasticized Biomolecules in Relation to Cellular Water Organization, Cytoplasmic Viscosity, and Desiccation Tolerance in Recalcitrant Seed Tissues

Abstract

To understand the relationship between the organization of cellular water, molecular interactions, and desiccation tolerance, dielectric behaviors of water and water-plasticized biomolecules in red oak (Quercus rubra) seeds were studied during dehydration. The thermally stimulated current study showed three dielectric dispersions: (a) the relaxation of loosely-bound water and small polar groups, (b) the relaxation of tightly-bound water, carbohydrate chains, large polar groups of macromolecules, and (c) the "freezing in" of molecular mobility (glassy state). Seven discrete hydration levels (water contents of 1.40, 0.55, 0.41, 0.31, 0.21, 0.13, and 0.08 g/g dry weight, corresponding to Ϫ1.5, Ϫ8, Ϫ11, Ϫ14, Ϫ24, Ϫ74, and Ϫ195 MPa, respectively) were identified according to the changes in thermodynamic and dielectric properties of water and water-plasticized biomolecules during dehydration. The implications of intracellular water organization for desiccation tolerance were discussed. Cytoplasmic viscosity increased exponentially at water content Ͻ 0.40 g/g dry weight, which was correlated with the great relaxation slowdown of water-plasticized biomolecules, supporting a role for viscosity in metabolic shutdown during dehydration.

TSDC spectroscopy of relaxational and interfacial phenomena

“…The implications of intracellular water organization for desiccation tolerance were discussed. Cytoplasmic viscosity increased exponentially at a water content < 0.40 g/g dry weight, which was correlated with the great relaxation slowdown of water-plasticized biomacromolecules, supporting a role for viscosity in metabolic shutdown during dehydration [395].…”

“…Sun [395] studied red oak (Quercus rubra) seeds analysing the relationship between the organization of cellular water, molecular interactions, desiccation tolerance, dielectric behaviours of water and water-plasticized biomacromolecules in these seeds during dehydration. The TSDC study showed three dielectric bands: (a) the relaxation of loosely-bound water and small polar groups; (b) the relaxation of tightly-bound water, carbohydrate chains, and large polar groups of macromolecules; and (c) the "freezing in" of molecular mobility (glassy state) (Fig.…”

The Relationship Between Bound Water and Carbohydrate Reserves in Association with Cellular Integrity in Fragaria vesca Stored Under Different Conditions

“…Changes in the bound water fraction are at least partially the result of modifications in the levels of hydrophilic molecules with high water-binding capacity. It was reported that the bound water that represents unfreezable water (Wolfe et al 2002) plays an important role in tolerance to different environmental stresses, such as freezing and drought (Rascio et al 1998;Sun 2000). Indeed, fruit stored at low temperature under adequate high CO 2 concentrations had a larger bound water fraction (Goñi et al 2011), in association with an increase of inulin series fructans, which consist of linear β (2-1) linked fructose residues with a terminal glucose residue (Blanch et al 2011).…”

Thermodynamics of Seed and Plant Growth

“…1 and 5) is presumably associated with the saturation of all primary hydration sites. No consistent differences in the water sorption characteristics has been found between recalcitrant and orthodox seed tissues (Sun, 2000). Contrary to experimental data realized on viable seeds, Krishnan et al (2004aKrishnan et al ( , 2004c established that germinating and non-germinating seeds contained three types of water (bound, bulk and free water) in phase I of hydration.…”

“…From this point, seed viability could be maintained during long periods owing to their glass structure, which was defined by Buitink & Leprince (2004) as a thermodynamically unstable state, with high viscosity (enabled by low tissue moisture and low temperature), so as the viscosity is so high that diffusional movement is effectively prevented for time periods or practical utility. Sun (2000); Walters (2007); Buitink & Leprince (2008) ascertained that glass stability is not upheld per se, it is based on groups of different biomolecules, linked by hydrogen bonds with water molecules. Bryant et al (2001) and Benson (2008) suggested that the formation of a glassy matrix (i.e., vitrification) in could represent a strategy for desiccation tolerance and storage stability, in general.…”