Page 11 - LN-cH-11

Significance of Plasmolysis
(i) It allows a plant cell to lose water without dying, it can shrink or increase in size as
water is available within the constraints of the cell wall.
(ii) It is shown by living cells. By this we can determine whether a cell is living or
dead.
(iii) It helps in determining osmotic pressure of plants.
(iv) It proves that cell wall is elastic and permeable.
Imbibition
It is a special phenomenon in which water or any other liquid is absorbed by the solid
particles (colloids) of a substance. This leads them to increase enormously in
volume. The solid particles which imbibe water or any other liquid are called
imbibants. The liquid, which is imbibed is known as imbibate. It is also a type of
diffusion because movement of water occur along concentration gradient as in
diffusion. During imbibition, water molecules get tightly adsorbed and becc
immobilised.
Note:
* During imbibition water molecule lose most of their kinetic energy in the form of
heat. This is called heat of hydration or heat of wetting
* Imbibition can be best explained and seen in absorption of water by seeds and
drywood which acts as absorbents to imbibe water and swell.
Imbibition Pressure
The pressure developed by solid particles, which adsorbs water or any other liquid
when submerged in pure imbibing liquid is called imbibition pressure. It is due to this
pressure in plants that seedlings emerge out of the soil and establish themselves.
Conditions necessary for imbibition to take place are
(i) Affinity between the adsorbant and the liquid imbibed is essential.
(ii) Water potential gradient between the absorbent and the liquid imbibed.