Determination of water "bound" by soluble subcellular components during low-temperature acclimation in the gall fly larva, Eurosta solidagensis.

The third instar larvae of the goldenrod gaIl fly, Eurosta solidugensis, overwinter inside stem galls on goldenrod plants and display a cold hardiness which allows the insects to survive prolonged freezing at temperatures as low as -30°C (17). A number of metabolic adjustments have been linked to the process of freezing tolerance in animals or frost hardiness in plants including: changes in amounts and types of lipids (6, 23), increases in the content of polyhydric alcohols, and/or other sugars with corresponding decreases in glycogen or starch content (6, 14), changes in the amounts and types of amino acids present (6, 14), and increases in the amount of water “bound” by subcellular components (14, 16, 18). In E. solidagensis, there is a well-documented increase in the concentrations of the polyols, glycerol and sorbitol, with acclimation to low temperature (3, 17), and changes in the levels of other sugars, glycogen, and amino acids have also been demonstrated (21). The role of bound water as a mechanism of cold hardening has been investigated in both plants and animals. Bound water is thought to be that water which is “ordered” by cellular components and which, because of ordering, displays altered features as compared to “bulk” water, in-