Osmosis On Plant Tissue Experiment
Investigate the effect of a range of concentrations of salt or sugar solutions on the mass of plant tissue.
Students are required to investigate the effect of osmosis and water potential on the mass of plant tissue. They are required to use appropriate apparatus to prepare dilutions of sugar or salt solution and assess the effects of different concentrations by measuring the change and calculating the percentage change in length and mass of potato cylinders before plotting their results on a graph.
Equipment (per pair of participants)
If preparing own potato cylinders
• A potato
• Scalpel
• Forceps
• Cork borer
• White tile
• 15cm ruler
• Boiling tubes and rack
• 10ml measuring cylinder
• Top pan balance (measuring to two
decimal places)
• Sodium Chloride/Sucrose
• Deionised water
• CLEAPSS Hazcards: 40C, 47B
Investigating the Effect of Solutions on Potato Cylinders
Method
- Preparing the Potato Cylinders
- Cut the Cylinders
- Use a cork borer to prepare five identical potato cylinders from a single potato.
- Trim and Measure
- Carefully trim off the potato skin using a scalpel, ensuring all cylinders are uniform in size.
- Measure and record the initial length of each cylinder in a suitable table.
- Preparing the Solutions
- Create Serial Dilutions
- Start with a 1 molar solution of either sucrose or sodium chloride.
- Use serial dilution to prepare four different concentrations of the solution, including the 1 molar concentration.
- Label the Boiling Tubes
- Prepare and label five boiling tubes:
- One as ‘water’ or ‘zero’ concentration (control).
- The others with the specific concentrations of the prepared solutions.
- Recording Initial Measurements
- Weigh the Potato Cylinders
- Use a 2 decimal place balance to weigh each potato cylinder.
- Record the initial mass of each cylinder in your results table.
- Add Solutions
- Measure 10mls of each solution accurately and pour them into the appropriately labelled boiling tubes.
- Add 10mls of water to the tube labelled ‘water’ or ‘zero’.
- Place the Cylinders in Tubes
- Place one potato cylinder into each boiling tube.
- Allow the Experiment to Proceed
- Set the Time and Conditions
- Leave the tubes for a set amount of time.
- If possible, use a water bath at 30°C to speed up and amplify the results.
- Recording Final Measurements
- Remove and Measure
- After the set time, remove each potato cylinder carefully from the tubes.
- Measure and record their final length and final mass.
- Record Data in a Table
- Ensure all measurements are accurately noted for each concentration.
- Calculating Changes
- Determine Changes
- Calculate the change in mass and change in length for each cylinder.
- Percentage Change
- Use the formula to calculate percentage change:
- Percentage Change=(Change in ValueInitial Value)×100\text{Percentage Change} = \left(\frac{\text{Change in Value}}{\text{Initial Value}}\right) \times 100Percentage Change=(Initial ValueChange in Value)×100
Technician tips
• 1L of accurate 1M sucrose solution is made by adding 342.3g of sucrose to 750mls of deionised water, heating slightly and stirring to dissolve and transfer the solution via a funnel into a volumetric flask. Use a wash bottle to rinse any remaining sucrose solution from the beaker and funnel into the volumetric flask and then fill the volumetric flask to the meniscus line. Insert the stopper and invert the flask several times to fully mix.
• 1L of accurate 1M sodium chloride solution is made by adding 58.44g of sodium chloride to 750mls of deionised water, heating slightly and stirring to dissolve and transfer the solution via a funnel into a volumetric flask. Use a wash bottle to rinse any remaining sodium chloride from the beaker and funnel into the volumetric flask and then fill the volumetric flask to the meniscus line. Insert the stopper and invert the flask several times to fully mix.
• This accurately prepared solution can then be diluted by students to prepare the lower molarity solutions.
• Potato cylinders could be prepared for students in advance to negate the need for the use of sharp implements in the classroom. Pre-preparing the cylinders also ensures that potato waste is kept to a minimum. The cylinders need to be completely skinless for them to be the most effective.
• If students are preparing their own cylinders, a supply of plastic straws can be helpful to remove the potato cylinders from the cork borers.
• An electronic water bath could be provided and set at 30°C. Placing the tubes in the water bath and leaving them for 30 minutes will give a more noticeable change in mass and length.
To do this practical, you will need
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Investigate the effect of a range of concentrations of salt or sugar solutions on the mass of plant tissue. The experiment involves using an apparatus to prepare dilutions of sugar or salt and assess the effect of different concentrations. To do this practical students will need safety googles, ruler, class dissection bundle, cork borer set, boiling tube, boiling tube rack, 10ml measuring cylinder, white tile, top pan balance, sodium chloride, sucrose, deionised water, digital water bath and volumetric flask. Shop our full range of biology equipment at Philip Harris.
