Michael said:

The logic works for me, but experience tells me otherwise. I have
bent
some extremely old branches with tight growth rings. The trees that
were allowed to dry out before the stylings were significantly easier
to
bend. I attribute this to the amazing strength of the water swollen
inner bark.

The first step is to reason something out, as I did in my post, but
the second step is to test the hypothesis. There are two hypotheses I
can come up with: one, that increased tension in the water columns of
the xylem with drying-out makes the branch more flexible, or two, that
turgor of the inner bark has some effect on the breakability of the
bark (I can't think of any way that the inner bark could influence the
wood, sorry!).

I like the former hypothesis. To test it, I'd use tomato plants.
Tomatos transport water to the leaves by two different methods:
positive pressure, pushing water up the stem by an osmotic pump or:
negative pressure, using transpiration to PULL water up the stem. If
the pressure of water in the xylem has an effect of flexibility, then
I'd expect the tomatos using the ionic pump to snap easily, and the
tomatoes using transpiration to snap. I have tools to measure soil
water potential and leaf water potential; I have tools that can
measure the pressure I'm putting on stems. The only problem I can see
is that I'd be exposing the plants to different levels of humidity,
and that would be a complicating factor.

However, if I got promising results with the tomato, I could try:
sugar maple saplings!!!! In spring, before leaves emerge, maples use
an osmotic pump to move water up the stem ("the sap is running").
After leaves emerge, maples use a transpiration pump.

Now you've got me all excited! Except today I am grinding up soybean
roots to use the tissue for PCR analysis!


Nina. Yes. I dream about experiments.