Question

Based on the microstructure of wood, explain the mechanisms responsible for retention of water within the structure of wood.

Answer 1

Wood is a hygroscopic substance which means it absorbs water.

retention of water within the structure of wood varies with the category of wood.

The category is classified with the properties of wood:-

1.Softwoods

2.Hardwoods

In softwood,

The typical softwood structure is fairly simple.

The vertical system consists mainly of axial tracheids, and the radial or horizontal system consists of rays, the bulk of which are ray parenchyma cells.

In Hardwoods,

A typical hardwood structure is much more complex than a softwood one.

The axial system is composed of various kinds of fibrous components, vessel components in different sizes and configurations, and axial parenchyma in different patterns and abundance.

As in softwoods, rays make up the radial network and consist of ray parenchyma cells, but hardwoods exhibit greater variation in cell size and form.

Water gets into the wood in three ways:

1) fluid through the cell lumens through capillary tension

2) vapor through the cell lumens

3) molecular diffusion through the cell walls

Moisture Relations:-The cell wall consists mainly of cellulose and hemicellulose, and the cell wall is hygroscopic by the hydroxyl groups on these chemicals. Lignin is a comparatively hydrophobic molecule, the factor that cements the cells together.

This means the cell walls in wood have a great affinity for water, but the walls' capacity to soak up water is partly restricted by the presence of lignin. Forest water has a significant effect on forest resources, and wood-water interactions have a huge impact on the industrial use of wood in wood products

Wood's equilibrium moisture content is a condition that correlates to air temperature and relative humidity, in which the wood's moisture content stays stable& relative air humidity is the ratio of the amount of water in the air to the average amount of water that the air at the prevailing air temperature will hold up to.

The saturation point at + 20 C in the major Finnish tree species is around 30 percent. Wood's ability to absorb and moisture capacity can be used as a structural advantage.

example :-thermal insulation