Learn: Required Practical 3 - Water Potential in Plant Tissue (Calibration Curve)

Welcome!Great to see you back! You've already learned about cell membranes, osmosis, and transport. Today, we'll build on that understanding by exploring Required Practical 3: Water Potential in Plant Tissue. Let's discover how to determine water potential using a calibration curve!

What is Water Potential?Water potential measures the tendency of water to move from one area to another due to osmosis. It is measured in units of pressure (kPa) and can help us understand how water moves in and out of cells. Pure water has the highest water potential of 0 kPa, while solutions with solutes have negative water potential values.

Why is this Practical Important?This experiment helps us understand how water moves in and out of plant cells. By determining the water potential of plant tissue, we can see how cells interact with their environment and maintain their shape and function. This is crucial for understanding cell membranes and transport, which you've already studied!

Steps in the Practical1. Cut uniform pieces of plant tissue (e.g., potato cylinders).2. Prepare sucrose solutions of known concentrations.3. Place the plant tissue in each solution for a set time.4. Measure the change in mass of the tissue after soaking.5. Calculate the percentage change in mass.6. Plot the calibration curve to determine the water potential.

How to Calculate Percentage Change in MassTo find the percentage change in mass, use the formula:Percentage change = [(Final mass - Initial mass) / Initial mass] × 100This tells us how much the mass of the potato has changed after being in the solution. A positive value means the potato gained water, while a negative value means it lost water.

Creating a Calibration CurveA calibration curve is a graph showing the relationship between sucrose concentration and the percentage change in mass of the plant tissue. It's used to find the sucrose solution where the mass change is zero, which matches the water potential of the plant tissue.

Why Does Mass Change?Osmosis causes water to move across the cell membrane. If the sucrose solution is more concentrated (lower water potential) than the plant tissue, water leaves the cells, causing a loss in mass. If the solution is less concentrated (higher water potential), water enters the cells, increasing the mass.

Review Time!Great work! You've learned about water potential, osmosis, percentage change in mass, and calibration curves. Let's test your understanding with a few questions!

Well Done!You've completed the lesson on Required Practical 3! You've mastered water potential, osmosis, calibration curves, and calculating percentage change in mass. Keep practising and you'll be ready for any challenge.