[NAFEX] Hardening-off Question

Thomas Olenio tolenio at sentex.net
Wed Aug 10 17:53:48 EDT 2005


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 at 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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