Imbibition

a. Imbibition : Imbibition is the very first step by which a root hair takes up water, and it is a purely physical, non-living process: it is the swelling of a hydrophilic (water-loving) colloidal material caused by the adsorption of water onto that material's surface. The substance doing the adsorbing is called the imbibant, and the water or liquid being adsorbed is called the imbibate.

The wall of a root-hair cell is made of pectic compounds and cellulose, both of which are hydrophilic colloids and therefore excellent imbibants. As imbibition proceeds, water molecules become tightly bound to these wall materials without ever forming a true solution — the water is adsorbed onto internal surfaces, not merely dissolved. This uptake continues, moving along a concentration gradient, until an equilibrium is reached between the wall material and the surrounding water. …