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nafex - Re: [NAFEX] Hardening-off Question

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  • From: "Thomas Olenio" <tolenio@sentex.net>
  • To: "North American Fruit Explorers" <nafex@lists.ibiblio.org>
  • Subject: Re: [NAFEX] Hardening-off Question
  • Date: Wed, 10 Aug 2005 17:53:48 -0400

Hi,

If you want a further guess, I would bet dropping temperatures affects internal hormones of the tree that result in domancy.

Sun, cold and time all affect tree hormone production.

My guess is that the cold quickly destroys the hormones actively telling plant cells to grow and hold moisture. When tempertures rise, growth resumes with replenished hormone levels.

Just an uneducated guess.

Later,
Tom


On Wed, 10 Aug 2005 17:29:01 -0400, Ginda Fisher <list@ginda.us> wrote:


On Aug 10, 2005, at 9:46 AM, Lucky Pittman wrote:

At 07:18 AM 8/10/2005, J.Fruth wrote:

Here's a question a lot of us wold like to know the answer to:
Does
anyone have an answer? "Physiologically speaking, what happens
inside the
branches, twigs, trunk, etc. of fruit trees as the harden off for the
winter?"


Jim,
I'm not a plant physiologist/pathologist, but I suspect the answer
lies in
the degree of lignification - development of increasing amounts of
lignins
- the compounds which give woody plants(as well as grasses) much of
their
structural integrity.

Lucky

I am also no specialist, but I would guess that another part of the
answer is the amount of water in the tissue. I bet the tree dries
itself out, increasing the concentration of other "stuff" dissolved
in the sap to increase the freezing point of the remaining liquids
and to decrease the damage that swelling of freezing liquids would
otherwise cause.

This is purely a guess, but I know that in animal cells a lot of the
damage from freezing is actually mechanical damage to the cell
membranes caused by swelling water and ice crystals.

Ginda



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