What term describes wood that is altered to counteract a lean in a tree?

• A. Reaction wood
• B. Compression wood
• C. Tension wood
• D. Normal wood

Answer: (A)

When a tree leans, it forms reaction wood as a response to the mechanical stress. This wood is altered in structure and properties so it helps reorient the stem toward an upright position. In gymnosperms, the reaction wood on the lower side is called compression wood and tends to push the trunk upward, though it can be brittle and cause lumber warping. In many hardwoods, the reaction wood on the upper side is called tension wood and works to pull the stem upright, often with a distinctive gelatinous layer. Normal, unaltered wood doesn’t have this stress-driven change. So the term for wood modified to counteract a lean is reaction wood.