Water Potential of a Potato.

Essay by kevp88College, UndergraduateA+, October 2005

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Investigating the Water Potential of a Potato.

I have been asked to investigate the water potential of a potato. During my investigation I will not actually be able to measure a value for, as it is a pressure value (kPa).

Osmosis is a special form of diffusion involving only water molecules. It is defined as "The passage of water from a region of high water potential to a region of low water potential through a partially permeable membrane"

Definition of Water Potential.

The potential for water to move across a selectively permeable membrane, where the osmotic potential of distilled water is 0 (kPa) and any water movement is measured with a negative value.

When a solute is mixed with a solvent the water potential will decrease, and will always be a negative value.

Solute Potential.

As the presence of a solute lowers the water potential, the more concentrated the solute is, the lower the water potential will be.

Pressure Potential.

This is if pressure where applied to a solution it would resist the movement of water. There is an equation that can represent to relationship of water potential, solute potential and pressure potential:

= s + p

Osmosis and Plant Cells

Like animal cells, plant cells contain a number of solutes. When these cells are put into pure water, water moves into the cell because there is a lower water potential in the cell. But unlike animal cells, plant cells cannot control the amount of fluid surrounding the cell.

If a plant cell is placed in a solution with a lower water potential than the plant cell, water will move leave the cell, and the cell becomes plasmolysed (flaccid).

If the plant cell is place in a solution with the same water potential, there will be no net movement of...