The Effect of Different Solutions on Potato and Cucumber Strips

The Effect of Different Solutions on Potato and Cucumber Strips

Plan

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Introduction

Plants in the soil have their roots in a dilute solution of various

mineral ions. Sometimes, the soil they are planted in gets flooded

with sea water (which has an average of 0.3 sodium chloride

concentration). In these cases the roots are observed to wilt and

become flaccid. In my experiment, I will simulate this situation using

potato and cucumber strips, placing them in different solutions

(sodium chloride, glucose and sucrose) at different molar

concentrations.

A substance dissolved in water is called a solute. A solvent is a

liquid that is able to dissolve another substance, a solute, to form a

solution.

Water potential is a measure of the ability of a solution to give out

water. Water potential (y) can be expressed as the sum of the solute

potential (ys) and the pressure potential (yp). (y) = (ys) + (yp)

The water potential of pure water is zero and all other solutions have

a negative water potential. The greater the solute concentration, the

more negative is the value for water potential.

Background Information

The water content of plants depends on environmental conditions. In

land plants, water plays a vital role in structural support and

mineral transport, thus, the lack of water may lead to wilting or

possibly death.

Water is mainly absorbed through the roots by Osmosis. Osmosis is the

diffusion of water molecules from and area of high water potential to

an area of low water potential through a partially permeable membrane.

The roots are covered in specially adapted root hair cells, which

increa...

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* Some results could have been inaccurate due to not allowing excess

solution on the external surface of the cores from draining away

before placing it onto the top pan balance. This superficial water

would be measured as extra mass by the sensitive weighing scales, even

if the cores have been blot-dried on filter paper beforehand.

* Once the cells have been plasmolysed, it is possible that some of

the solution has entered the cell between the cell wall and the cell

membrane, given that the cell wall is fully permeable. This could lead

to inaccuracy of results, as part of the mass in the plasmolysed plant

cores would be caused by this intake of water, which has not been

caused by osmosis.

* The experiment was also lmited by the accuracy of the top pan

balance, which showed mass in grams to one decimal place.