Reaction wood

Reaction wood is a type of wood that forms in response to mechanical stresses in trees. It is formed in the main stem of a leaning tree or branch and has different properties than normal growth, being more brittle, denser, and prone to cracking. Reaction wood forms in different parts of the tree in softwoods and hardwoods, and it differs physically, microscopically, and chemically.


 * In gymnosperms (conifers), reaction wood forms on the underside of the limb or trunk and is called compression wood (CW).
 * In angiosperms (hardwoods), it is formed on the top of limbs and branches and is called tension wood (TW).

Compression wood is laid on the underside (compression side) of the bend in softwoods, while tension wood is formed on the upper side of the leaning, bent stem or branch in hardwoods. Eccentric and darker zones in the larger cross-cut section show compression wood, while markings on the smaller cross-section are not as apparent.