Why is the cell wall of the root hair cell ( plant) so thin ?

It is thin to enable it to absorb nutrients easily.

Why is the cell wall of the root hair cell ( plant) so thin ?

in order for water and minerals to pass easily

Why is the cell wall of the root hair cell ( plant) so thin ?

As already mentioned. The cell wall is thin and permeable in order to allow water and nutrients to move through the cells and into the circulatory system of the plant. All to do with osmotic pressure if memory serves me right.

Here's a great site with diagrams:

http://www.classteacher.com/virtualschoo...

Here's a heavy but in depth explanation.

http://www.steve.gb.com/science/water_po...

Anyway hope that makes it a little clearer.

There's a great horticultural book that explains lots of planty stuff called The Principles of Horticulture by Adams,

Bamford and Early.