Keywords:
osmosis, plant tissue, sucrose solution, petri dish, concentration, mass, percentage change, water movement, scientific principles
Introduction:
Osmosis is a biological process where water molecules move across a partially permeable membrane from an area of high concentration to an area of low concentration. In this practical investigation, we aim to investigate the process of osmosis in plant tissue. By studying this process, we can gain a deeper understanding of how water moves in and out of cells and how this affects the overall health and growth of plants.
Equipment needed:
- Potato
- Scalpel
- Ruler
- Boiling Tube
- Sucrose solution
- Distilled water
- Paper towel
Method:
- Cut the potato into small cubes of equal size using a scalpel and ruler. 1-2cm3 works well.
- Place the potato cubes in a boiling tube and cover them with a sucrose solution of known concentration.
- Leave the petri dish for an hour and record the initial mass of the potato cubes.
- After an hour, remove the potato cubes from the petri dish and place them on a piece of paper towel to remove any excess liquid.
- Record the final mass of the potato cubes.
- Calculate the percentage change in mass using the formula: Percentage change in mass = ((final mass – initial mass) / initial mass) x 100%
Expected findings:
If the sucrose solution is more concentrated than the potato cells, the water will move out of the cells, and the potato will lose mass. If the sucrose solution is less concentrated than the potato cells, the water will move into the cells, and the potato will gain mass.
In summary
Conclusion:
Based on our findings, we can conclude that the concentration of the solution surrounding the plant cells affects the process of osmosis. If the solution is more concentrated than the cells, water will move out of the cells, causing them to lose mass. If the solution is less concentrated than the cells, water will move into the cells, causing them to gain mass.
Questions:
- What is osmosis?
- How does the concentration of the solution affect the movement of water molecules in osmosis?
- Why is osmosis important for plant growth and health?
- What is the purpose of placing the potato cubes on a piece of paper towel after removing them from the petri dish?
- What would happen to the potato cubes if the sucrose solution was the same concentration as the potato cells?
Answers:
- Osmosis is the movement of water molecules across a partially permeable membrane from an area of high concentration to an area of low concentration.
- The concentration of the solution affects the direction of water movement in osmosis. If the solution is more concentrated than the cells, water will move out of the cells, causing them to lose mass. If the solution is less concentrated than the cells, water will move into the cells, causing them to gain mass.
- Osmosis is important for plant growth and health because it allows water and nutrients to move in and out of plant cells, which is essential for their survival.
- Placing the potato cubes on a piece of paper towel after removing them from the petri dish is important to remove any excess liquid and prevent it from affecting the mass measurements.
- If the sucrose solution was the same concentration as the potato cells, there would be no net movement of water in or out of the cells, and the mass of the potato cubes would remain unchanged.
By conducting this practical investigation, we can gain a better understanding of the process of osmosis in plant tissue and how it affects the overall health and growth of plants. It is a simple and effective way to study the movement of water in and out of cells and can be used to help explain a wide range of biological processes.
In conclusion, investigating osmosis in plant tissue is an important and informative practical investigation for anyone interested in biology and plant science. By following the steps outlined in this guide, you can conduct your own investigation and gain a deeper understanding of this crucial biological process.
Related Practicals
What is Osmosis?
Understand the theory behind osmosis before doing the practical
Cells Under a Microscope
Observe the cell structures involved in osmosis at high magnification
pH and Enzyme Activity
Another IGCSE prescribed practical investigating biological molecules
Food Tests Practical
Test for biological molecules in food samples
Guidance
IA Guidance
Osmosis in plant tissue is one of the most popular IB Biology IAs. To turn this IGCSE prep into a strong IA:
- Research Design: Use sucrose solutions of varying molarity (e.g. 0.0, 0.2, 0.4, 0.6, 0.8, 1.0 mol dm⁻³). Cut potato cylinders with the same cork borer to standardise surface area. Standardise the starting mass and length. Justify your concentration range to span both hypotonic and hypertonic conditions so the isotonic point is captured.
- Data Analysis: Plot percentage change in mass against sucrose concentration. The x-intercept (where %Δm = 0) gives the water potential of the tissue. Include uncertainty bars from balance precision (typically ±0.01 g) and from biological variability across replicates.
- Conclusion: Quote the water potential of the tissue ± uncertainty. Compare to literature values for potato (typically around −0.7 MPa) and discuss whether your value is within accepted range.
- Evaluation: Dominant systematic errors are usually surface water on the tissue after rinsing (blotting consistency), temperature drift, and the assumption of uniform initial water potential across the potato. Suggest a temperature-controlled water bath and a fixed blotting protocol (e.g. five gentle rolls on filter paper).
About the Author
Marc Curran is a science teacher with nearly 20 years of classroom experience across the UK, Bangkok, Shanghai and Hong Kong. He has taught IB, IGCSE and GCSE Science at some of the world’s leading international schools. Practical Science is his free resource library of over 100 laboratory practicals, trusted by more than 600,000 visitors since 2016.
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