D Mc

Thanks guys for the responses.

This whole question came about as I (SMc) was working on an assignment re Constant Strain Hypothesis. So we got into a big discussion about if a conifer puts on "compression" wood in response to stress and it has an injury on the "compressive" (underneath) side of its trunk, is that far worse than if it had the injury on the tensile (upper) side? (Thinking that it would have put compression wood on in response to stress and was not able to because of the injury.) We are supposing the opposite then would be true for an angiosperm.

This discussion then progressed to upper and lower sections of limbs. We have not seen a large, lateral limb that does not have more wood on the bottom. The tree's response to the "stress" of trying to hold this heavy limb being to put more wood on the bottom. This holds true (I believe) no matter whether it is a conifer or angiosperm. But we still call the upper wood "tension" wood and the bottom wood "compression" wood, right?

When a limb on a conifer dies it droops down, when a limb on an angiosperm dies it tends to bend up (not necessarily as dramatically).

We realize there is a cellular difference between conifers and angiosperms. However, the underside of a branch is going to be shaded no matter which it is. So the auxins causing the elongation of xylem cells (correct Mario) would seem to have to react the same. But the text is telling us they achieve the same results (straightening the trunk, or holding the limb) in a different manner.

That's what we want to know. How did they determine this.

So off we go to Ekka's links on tension wood.

S Mc