Woody Reactions (in Trees)
Updated: Nov 21, 2021
Have you ever wondered how trees keep themselves upright? Even through massive weather events throughout their lives? How do trees reach and capture the optimal amount of light?
Well, the answer is very "Woody"! Hope the information below keeps you "Upright" in your seats and keeps your attention "Standing tall"!
The Axiom of Universal Stress
The axiom of uniform stress is based on the theory that trees carry out their secondary growth in such a way that bending stresses are averaged out over the outer surfaces of the tree and the tree's resulting aerial form avoids stress concentrations and repairs “notch stresses”.
A Woody Reaction
Reaction wood in a woody plant is wood that forms in place of normal wood as a response to gravity, where the cambial cells are oriented other than vertically. It is typically found on branches and leaning stems. It is an example of mechanical acclimation in trees.
Progressive bending and cracking would occur in parts of the tree undergoing predominantly tensile or compressive stresses were it not for the localised production of reaction wood, which differs from ordinary wood in its mechanical properties. Reaction wood may be laid down in wider than normal annual increments, so that the cross section is often asymmetric or elliptical. The structure of cells and vessels is also different, resulting in additional strength. The effect of reaction wood is to help maintain the angle of the bent or leaning part by resisting further downward bending or failure.
There are two different types of reaction wood, which represent two different approaches to the same problem by woody plants: Compression Wood or Tension Wood.
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