PLANT WATER RELATIONS
Water is essential for all physiological activities of the plant, and plays a very important role in all living organisms. To
comprehend plant-water relation, an understanding of the following standard terms is necessary.
Membrane permeability is the ability of a membrane to allow passage of gases, liquids, solutes or dissolved substances througt. On the basis of their permeability, membranes are of following ypes
Impermeable : do not allow passage of substances, e.g cuticle layer Permeable : allow the passage of substances, e.g., ceilulose cell walls. Semipermeable : allow passage of only solvent molecules, but not the solute particles, eg, egg membrane, parchment Impermeable Permeable Semipermeable Selectively
permeable Types of membranes on the basis of their permeability membrane Selectively or differentially permeable : allow passage of solute molecules only upto a certain extent, e.g. plasma membrane.
Imbibition is the phenomenon forming a solution. Solid substances or adsorbents, which take part in imbibition are called imbiwood. The liquid, usually water, which is imbibed is known as imbibate. of adsorption of water or any other liquid, by the solid particles of a substance, without
bants, e.g., seeds, dry molecules of water or any other liquid i.e., imbibate are held in between, or over the surface of solid substances, l.e, imbibants, through the of processcapillarity, or by the force of adsorption. Hence, we can say that imbibition is a phenomenon of adsorption. imbibants are hydrophilic colloids. They have a highly negative water potential so, when they come in contact with ter (w, O a steep water potential gradient is established. Water diffuses rapidly into the adsorbent till equilibrium is attained Amount of depnd imbibitionends upon Water potential gradient between adsorbant and water
Affinity of adsorbant for water
Imbibition increases the volume of the imbibant, but the increase is less than the volume of water absorbed. During
mbibition, the water molecules get tightly adsorbed, and become immobilized.
