FROSTS
Jonathan Knisely (Tue, 13 Nov 2007 12:26:49 PST)

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