3 Determining the water potential of potato tuber cells
The production of a dilution series of a solute to produce a calibration curve with
which to identify the water potential of plant tissue.
Osmosis is the net movement of water molecules from an area of high concentration to an
area of low concentration across a partially permeable membrane. Water potential is the
measure of the tendency of water molecules to diffuse from one area to another and is
determined by factors such as the concentration of a solute.
What is meant by plasmolysis?:When a plant cell loses water via osmosis when in a
hypertonic solution, it shrinks.When in a hypotonic solution, water rushes into the cell and
when in an isotonic solution there is no net gain or loss of water.
The aim of this experiment is to produce a calibration curve, allowing us to investigate the
water potential of plant tissue.
Independent variable: Concentration of the sucrose solution
Dependent variable: change in mass of the potatoes
All other variables need to be controlled so they do not affect results and make them
inaccurate. These include:
● Size of cut out potatoes (need to be as similar as possible-use a ruler with cutting
into smaller pieces)
● volume/amount of solution (measure using a 5cm² syringe)
● Temperature (can affect activity so needs to remain constant-use a water bath and
measure regularly using a thermometer)
● Time between taking of initial and final mass (needs to be the same for all the potato
chips as if more they would have more time for osmosis to occur- measure with a
timer)
Furthermore safety precautions need to be ensured including wearing adequate hand and
eye protection ( gloves, goggles), a lab coat and caution while handling glass equipment and
a scalpel.
Results Table
Concentration Initial mass/g Final mass/g Change in % change in
of sucrose mass/g mass
solution/
moldm-з
0.0 1.25g 1.35g +0.10g 8%
0.2 1.40g 1.48g +0.08g 5.71%
0.4 1.43g 1.33g -0.10g -6.99%
0.6 1.41g 1.29g -0.12g -8.51%
0.8 1.36g 1.21g -0.15g -11.03%
The production of a dilution series of a solute to produce a calibration curve with
which to identify the water potential of plant tissue.
Osmosis is the net movement of water molecules from an area of high concentration to an
area of low concentration across a partially permeable membrane. Water potential is the
measure of the tendency of water molecules to diffuse from one area to another and is
determined by factors such as the concentration of a solute.
What is meant by plasmolysis?:When a plant cell loses water via osmosis when in a
hypertonic solution, it shrinks.When in a hypotonic solution, water rushes into the cell and
when in an isotonic solution there is no net gain or loss of water.
The aim of this experiment is to produce a calibration curve, allowing us to investigate the
water potential of plant tissue.
Independent variable: Concentration of the sucrose solution
Dependent variable: change in mass of the potatoes
All other variables need to be controlled so they do not affect results and make them
inaccurate. These include:
● Size of cut out potatoes (need to be as similar as possible-use a ruler with cutting
into smaller pieces)
● volume/amount of solution (measure using a 5cm² syringe)
● Temperature (can affect activity so needs to remain constant-use a water bath and
measure regularly using a thermometer)
● Time between taking of initial and final mass (needs to be the same for all the potato
chips as if more they would have more time for osmosis to occur- measure with a
timer)
Furthermore safety precautions need to be ensured including wearing adequate hand and
eye protection ( gloves, goggles), a lab coat and caution while handling glass equipment and
a scalpel.
Results Table
Concentration Initial mass/g Final mass/g Change in % change in
of sucrose mass/g mass
solution/
moldm-з
0.0 1.25g 1.35g +0.10g 8%
0.2 1.40g 1.48g +0.08g 5.71%
0.4 1.43g 1.33g -0.10g -6.99%
0.6 1.41g 1.29g -0.12g -8.51%
0.8 1.36g 1.21g -0.15g -11.03%
