An Investigation to find the water potential of a plant cell.

Authors Avatar

Janine Regan                                                                                                 February 2003

Preston College 46651

An Investigation to find the water potential of a plant cell

Aim and Introduction

The initial aim of the experiment was to determine the water potential of a plant cell. (Measured in kPa, ψ). With the knowledge ofosmosis it was possible to discover the water potential of the cell.  Osmosis states that water molecules move from a region of a higher water potential/concentration to a region of a lower water potential/concentration through a semi permeable membrane, until equilibrium.

 As emphasised, “until equilibrium”, was the key part to the investigation, as it became the aim of the experiment.  It then made sense that if a plant cell, let’s say a potato sample was placed in a known created solution, such as in this case a sucrose solution and in due course no change in mass or volume in either the potato or solution occurs, we would then call this the isotonic solution.  It would show that because no change had occurred then the solution outside the potato cell was at equilibrium, or had the same water potential as in the cell, as no movement occurred across the membrane of the cell.  So this was the aim, to find the figure that matched the water potential inside the potato cell.  

For future reference it is necessary to point out the possible variables that could have affected the final results in any way:

  • Temperature
  • Surface area
  • Volume
  • Concentration

Apparatus

  • Petri dish, with a lid                ×7
  • Scalpel                                ×1
  • Tweezers                        ×1
  • 10ml pipette                         ×2
  • 1M sucrose                         (excess)
  • Distilled water                        (excess)
  • Potato                                ×1
  • Borer                                (approx.1cm width)
  • Paper towel                        ×1
  • Weighing scale                ×1
  • Weighing boat                        ×1
Join now!

Method

  1. Appropriate apparatus was collected.  (Stated previously)
  2. The percentage sucrose solutions, 0%, 10%, 20%, 40%, 60%, 80%, and 100% were created using 1M sucrose solution distilled water.  It was important pure water was used as its water potential was zero kilopascals, this would then not have any affect on the final results.
  3. Before the solutions were made, two pipettes were labelled.  One, ‘sucrose’ and the other ‘distilled water’.  Thus, preventing contamination when measuring and mixing solutions.
  4. The 0% sucrose solution was simply 30ml of distilled water, measured and poured out three times into a petri dish, ...

This is a preview of the whole essay