The Relationship between Water Binding and Desiccation Tolerance in Tissues

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Abstract
In an effort to define the nature of desiccation tolerance, a comparison of the water sorption characteristics was made between tissues that were resistant and tissues that were sensitive to desiccation. Water sorption isotherms were constructed for germinated and ungerminated soybean [Glycine max] axes and also for fronds of several species of Polypodium [P. polypodioides, P. pteropus, and P. vulgare] with varying tolerance to dehydration. The strength of water binding was determined by van''t Hoff as well as D''Arcy/Watt analyses of the isotherms at 5, 15, and/or 25.degree. C. Tissues which were sensitive to desiccation had a poor capacity to bind water tightly. Tightly bound water can be removed from soybean and pea seeds by equilibration at 35.degree. C over very low relative humidities; this results in a reduction in the viability of the seed. We suggest that region 1 water (i.e., water bound with very negative enthalpy values) is an important component of desiccation tolerance.