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

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