Wood which is grown having special features, lie special growth patterns and other such properties is known as reaction wood. As the name itself indicates, reaction wood is formed due to its ‘REACTION’ to various environmental factors lie wind, pressure, climate, gravity and many more. Special growth patterns which are usually witnessed on branches and trunks of various trees are made due to the stress produced by environment. There are two types of reaction wood:
- Compression wood
- Tension wood
Now the main difference between compression and tension wood is, compression wood is the reaction wood of conifers while tension wood is the reaction wood of dicots.
What is Compression Wood?
Compression wood is usually formed in conifers on the lower side of the trunk. Wood with high lignin content is compression wood and that is why it is strong in compression. In conifers, compression wood is formed on the underside of its branches. As it is rich in lignin, one of its function is to prevent the branch from drooping. Pith is not present in the center but way above the center point, which indicated much more development on the top. In cross section, these branches form an oval shape. If compression wood would not have been formed then progressive bending and cracking would have occurred in the branches. Compression wood is usually formed on that side of the branch which bears the most pressure. It thereby helps in lengthening and straightening the bend. It has only 30% of cellulose. It helps in maintaining the angle of bending, providing more strength. Precisely, it is a a blessing.
What is Tension Wood?
Tension wood is usually formed in dicots on the upper side of the trunk which is leaning or bent. Tension wood contains more cellulose than compression wood therefore it is very strong in tension and can easily resist leaning or bending. Hardwoods like oaks form tension wood in them on the upper side of the branch. It prevents the branch from drooping or bending, they switch to develop more wood on the underside which is called normal wood. It is usually formed on the part of the plant which is under tension, pulling it towards the affecting force. It has higher amount of cellulose than normal wood, around 60%.
- Reaction wood in angiosperms is tension wood and reaction wood in gymnosperms is compression wood.
- Compression wood is formed on the lower side of trunk while tension wood is formed on the upper side of trunk.
- Compression wood is rich in lignin while tension wood is rich in cellulose.
- Compression wood is formed in conifers like pines. Tension wood in dicots like mango.