Study Of Imbibition In Seeds Or Raisins: Affecting Factors, Importance

Imbibition in seeds is a common phenomenon occurring throughout Biology. The process serves up to be the first and foremost step when it comes to germination of seed. It can be described as the absorption of water by a certain substance that does not lead to the formation of any solution. Wooden doors during rain and swelling of seeds are a common example of imbibition. Let's take a closer look at the determinants affecting imbibition, its importance, and an experiment to get more in-depth knowledge regarding the topic.

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What is Imbibition?

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The term imbibition can be defined as a process of diffusion which occurs when absorption of water takes place by solids and colloid substances. This in turn leads to an increase in the volume of water. It plays a crucial role in the germination of a seed by setting a base for the process. Diffusion can be defined as the movement of molecules from a place of a higher concentration, to a place of lower concentration.

Being a passive transporter of materials, the process does not require any energy. A good example of this is raisins. When dry raisins are kept fully immersed in a beaker or container for some time, after they are removed, an increase is observed in their mass. This happens because they have absorbed water. During this process, water molecules are overloaded and become capable of moving around freely. The kinetic energy of these molecules transforms into heat energy and is released into the atmosphere. This is popularly called humidity.

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Factors affecting rate of Imbibition

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There are certain factors that disrupt the normal flow of imbibition. These are described as follows:

• Nature of imbibant - The nature of the imbibant plays a major role in influencing the rate of imbibition. Nature changes in different organic substances. Starch is known to have a much lesser capacity as compared to proteins which are known for their greater capacity in imbibing. Cellulose is an organic substance with the least capacity to imbibe. It is because of this reason when imbibition takes place, pea seeds swell more than wheat seeds, as the former contains proteins and the latter contains starch. 
• Temperature - Temperature is directly proportional to the rate of imbibition. As the temperature increases, the rate of imbibition also increases. 
• Concentration of solute - Solute’s concentration is indirectly proportional to the rate of imbibition. When one increases, the other one falls down. For example, if the concentration of the solute is increased, a decrease is witnessed in imbibition. This happens primarily because of a decrease in the diffusion pressure gradient between the imbibant and the liquid being imbibed.
• Surface area - The rate of imbibition is again directly proportional to the surface area of the imbibant. When the surface area shows a rise, the imbibition will also increase. 

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Signifcance of Imbibition

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The significance of imbibition is as follows:

• The process of germination of a seed is initiated by imbibition
• When the roots absorb water in the initial stage, imbibition plays a dominant role
• Water retention due to the active presence of fruits also happens because of imbibition
• The transformation of ovules as they ripen into seeds also takes place because of imbibition. It acts as a driving force that pushes water into the ovules
• As imbibition takes place, it releases a force that helps in the cohesion of water to the walls present outside the elements of the xylem.

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Experiment

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Aim of the experiment: To study and analyze the imbibition of water with seeds.

Theory: We can perform this experiment with seeds belonging to three different species. We can take peas for proteins, rice for starch, and groundnut for fats. Remember to peel off the coating of the seed. 4 ml of each kind of seed is taken and is kept in airtight bottles. After these bottles are weighed. 

Every kind of seed is to be taken and placed inside a beaker after which an equal quantity of water must be poured keeping in mind that seeds are properly immersed. At an interval of 15 minutes, the seeds are taken out and blotted. By observation, you can see that there is a considerable increase in the weight of seeds. 

Result: The percentage increase in weight by each type of seed is determined and plotted graphically.

Explanation: After the dry seeds are peeled off their coats, and put into the water, it causes a physical barrier to absorption. We all know that seeds are responsible for absorbing all the water with the process of imbibition due to the colloidal nature associated with the protoplasm of seeds. 

As a result, the seeds become swollen because of the water and now absorption of water is done by osmotic process. The rate of absorption varies in each seed because of its individual and unique nature. They have different protoplasmic elements which monitor and regulate their capacity to imbibe. 

We can infer from the outcome that, absorption of water is maximum in the case of seeds with protein and minimum in the case of seeds with fat. This is because proteins have a high affinity towards water, unlike fats which are the least. Starch also absorbs water along the surfaces of hydrophilic colloids apart from cellulose.

You can also take dry raisins and conduct a separate experiment. Swollen raisins definitely show a rise in their mass and it is possible due to imbibition. 

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Things to Remember 

• Imbibition is a process where substances like colloids upon being exposed to water, absorb it, leading to an increase in the volume, without forming a solution. Good imbibing is really necessary to be present in the process like seeds, dry wood, etc. these are generally solid substances that take part in binding. 
• There are many factors that may affect the normal flow of this process. These are temperature, nature of the imbibant, solute concentration, and surface area. Temperature and the surface area involved, are directly proportional to the rate of imbibition. One automatically increases when the other shows a rise. 
• The process of imbibition is crucial when it comes to absorption of water by the roots, the initial stage of germination, and so on. It is also responsible for the retention of water in fruits. Imbibition only takes place in the presence of adsorbents where the temperature is high. 
• Diffusion is a contrast in nature when it comes to imbibition. It can be seen only in liquids, and not in solids. Imbibition, on the other hand, is an irreversible process and doesn't need any semipermeable membrane. It just requires colloidal and hydrophilic substances. 

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