I tend to favor Jim McKenney's explanation. What I have observed, and what I have read, is that there may be a difference among plants in their ability to tolerate subfreezing temperatures based upon the presence of 'antifreeze-like' soluble compounds that can prevent the nucleation of ice crystals in plant cells. Differences between kale and lettuce might be partially explained by something like this. I don't believe that the cells would 'want' to deplete themselves of water--what would they do when the temperature got higher at midday? I wonder whether the anecdotal benefit of dousing frosted plants (that are not frozen) with water is because of the significant heat capacity of water as it undergoes a phase change from liquid to solid. The splash of water would prevent the nucleation of intracellular ice--all that 'outside' water would need to freeze before the intracellular water (with those special solutes) would freeze. Jonathan Knisely Coastal Connecticut, USDA 6a