Imbibitions are a physical process mainly concerned with adsorption of water. If a living (e.g. seed) or a dead plant (e.g. dry wood) material is kept in water, it absorbs water and swells, up considerably leading to increase in volume.

These substances (seeds, dry wood etc) are called imbibants. The liquid (water) which is absorbed is termed as imbibed substance and the phenomenon is referred to as imbibitions. Imbibitions may be defined as a physical process in which living or dead plant materials take up water or liquid mainly by adsorption due to the presence of hydrophilic or lyophilic colloids inside them through the submicroscopic capillaries present on their general surface of the body.

In plants imbibitions of water takes place by the constituents of cell wall and protoplasm such as carbohydrates, proteins etc.

Conditions necessary for imbibitions

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i. The existence of a diffusion pressure gradient between the imbibant and the substance imbibed.

ii. The existence of certain affinity between components of the imbibant and the imbibed substance.

Dry plant materials and seeds posses too much negative water potential. As a result water moves into them, when the plant materials arc placed in water.

The movement of water into plant materials continues till a dynamic equilibrium is attained. An imbibing does not necessarily imbibe all kinds of liquids. For example, dry plant materials immersed in ether do not swell appreciably. However, rubber, a plant product does imbibe ether and swell appreciably if submerged in it. On the other hand rubber will not imbibe water.

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This shows there exists some affinity or attractive force between the imbibant (rubber) and the liquid ether a considerable amount of materials such as proteins, carbohydrates etc. occur as hydrophilic colloids inside the cells. They have a strong affinity for water. Imbibitions Pressure

It represents the pressure that an imbibant develops when submerged in water. This pressure can be of tremendous magnitude. This fact becomes clear from the splitting of rock brought about by inserting dry wooden stakes in the crcuiccs of rock and soaking them with water.

Why does rock split because too much imbibitions pressure develops due to imbibitions. The imbibitional pressure also helps in breaking soil profiles by germinating seeds.

Factors affecting the rate of imbibitions

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i. Temperature:

The rate of imbibitions increases with the increase in temperature.

ii. Concentration of the Solute:

The presence of solutes in water affects the rate of imbibitions the rate L more in pure water than in a solution. Increase in concentration of the solute decreases imbibitions. Imbibitions totally ceases at a very high concentration of solutes in external solution.

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Biological importance of imbibitions:

i. Imbibitions play a key role in the initial stage of water absorption by the roots.

ii. Imbibitions initiate seed germination.

iii. The imbibitions force is useful in adhering water to the walls of xylem elements.

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iv. It helps fruits to retain water.

v. It also plays a major role in young and actively growing tissues.