Imbibition and water potential .

Imbibition is a special type of diffusion when water is absorbed by solids-colloids causing an enormous increase in volume

1. Wellcome to my presentation

2. Topic Imbibition , water potential , turgor pressure, osmotic pressure , deffusion pressure deficit.

3. Presented by --- Md NAYEEM HASAN

4. Imbibition Imbibition  is a special type of diffusion when water is absorbed by solids-colloids causing an enormous increase in volume. Examples include the absorption of water by seeds and dry wood .

5. Imbibition Imbibition is the absorption of water by hydrophilic colloids. Examples of plant material which exhibit imbibition are dry seeds before germination. Different types of organic substances have different imbibing capacities. Proteins have a very high imbibing capacity,starch less and cellulose least. That is why proteinaceous pea seeds swell more on imbibition than starchy wheat seeds.

6. Certain substances if placed in a particular liquid absorb it and swell up. For example , when piece of dry wood or dry seeds are placed in water they absorb the water quickly and swell up considerably so that their volume is increased. These substances are called as imbibes and the phenomenon as imbibition these exists certain force of attraction in between the imbibing and the imbibed substances.

7. In plants this is because of the presence of a large number of hydrophilic colloids both in living as well as dead cells in the form of proteins, carbohydrates ,such as starch ,cellulose , pectic substances etc. which have strong attraction towards water.

8. Role of imbibition in plants life Imbibition plays a very important role in the life of the plants – The first step in the absorption of water by the roots of higher plants is the imbibition of water by the cell walls of the root hairs. Imbibition of water is very essential for dry seeds before they start germination. As a result of imbibition a pressure is developed which is called as imbibition as imbibition pressure.

9. Water potential Water potential  is the potential energy of water per unit volume relative to pure water in reference conditions. Water potential quantifies the tendency of water to move from one area to another due to osmosis, gravity, mechanical pressure, or matrix effects such as capillary action (which is caused by surface tension). The concept of water potential has proved useful in understanding and computing water movement within plants, animals, and soil. Water potential is typically expressed in potential energy per unit volume and very often is represented by the Greek letter ψ

10. Water potential integrates a variety of different potential drivers of water movement, which may operate in the same or different directions. Within complex biological systems, many potential factors may be operating simultaneously. For example, the addition of solutes lowers the potential (negative vector), while an increase in pressure increases the potential (positive vector). If flow is not restricted, water will move from an area of higher water potential to an area that is lower potential. A common example is water with a dissolved salt, such as sea water or the fluid in a living cell. These solutions have negative water potential, relative to the pure water reference .

11. Turgor pressure Turgor pressure is the main pressure of the cell contents against the cell wall in plant cell. Plant need water to maintain turgor pressure. Turgor pressure caused by fluid pushing against the cell wall. Without it plants will wilt

12. Osmotic pressure Osmotic pressure is directly proportional to the concentration of dissolved solutes in the solution. More concentrated solution has higher osmotic pressure then its pure solvent.

13. Osmotic potential The potential of water molecules to move from a hypotonic solution to a hypertonic solution across a semi permeable membrane.

14. Diffusion pressure deficit (DPD) or suction pressure It is related with osmotic pressure and turgor pressure of cell sap. The difference between diffusion pressure of pure water and solution is called diffusion pressure deficit. In other word DPD of the cell sap or the cells is a measure of the ability of the cells to absorb water and hence it is often calledas the suction pressure. If the solution is more concentrated its DPD increases but it decreases with the dilution of the solution.