The defect in timber that arises due to the swelling caused by growth of layers of sap wood over the wounds after branch is cut off is called as ...........
How Trees Heal: Defects from Wounds
Like any living organism, trees can suffer from wounds caused by improper pruning, broken branches, or other external damage. The tree's natural response is to heal by growing new wood over the injured area. This healing process, however, can create irregularities in the wood structure, which are considered defects in timber.
📝 Detailed Analysis of the Options
(a) Checks
Checks are cracks that form across the annual rings. They are not a result of growth over a wound but are caused by uneven drying during the seasoning process.
(b) Knots
Knots are a natural part of a tree's growth, formed where branches connect to the trunk. They are embedded branch bases, not a swelling caused by a wound from a branch being cut off.
(c) Shakes
Shakes are internal cracks that form between the annual rings, caused by stresses like wind or frost while the tree is growing. They are separations within the wood, not a surface swelling.
(d) Rind gall
This is the correct answer. A rind gall is precisely the defect described. When a branch is cut off improperly or the tree is wounded, it attempts to heal the area by growing new layers of sapwood over the injury. This results in a characteristic swelling or bulge on the surface of the timber. The wood inside this gall is often irregular and weak, making it a significant defect.
📊 Comparison of Timber Defects
| Defect | Description | Cause |
|---|---|---|
| Rind Gall | Swelling or bulge on the surface | New wood growth over a wound |
| Checks | Cracks across annual rings | Uneven seasoning (drying) |
| Knots | Embedded base of a branch | Natural branch growth |
| Shakes | Separation between annual rings | Stresses during tree growth (wind/frost) |
💡 Study Tips
- Rind Gall = Wound Swelling: The key association is that a rind gall is like a scar or callus on the tree, formed as it heals a wound.
- Knots vs. Galls: A knot is a natural part of the tree's structure (where a branch was). A rind gall is the result of an injury (where a branch was cut badly).
- Distinguish Cracks from Growths: Remember that checks and shakes are types of cracks, whereas a rind gall is a type of abnormal growth.