An Investigation into the Water Potential Of Root Vegetables.

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An Investigation into the Water Potential

Of Root Vegetables.

   The aim of this investigation is to find the water potential of two root vegetables and to evaluate any differences that are found. Root vegetables take in the water they need through a process known as osmosis. Water moves from an area of high water potential to an area of low water potential through a partially permeable membrane. The water potential of root vegetables depends on the concentration of solutes within their cells. Starch is not soluble so the starch content of the vegetables will not affect the water potential. Sucrose however is soluble.

   In the investigation I will find the isotonic solution for each vegetable based on the principle that when the vegetable is in a hypertonic solution it will lose water (and become plasmolysed) and therefore lose mass and that when the vegetable is in a hypotonic solution it will gain water (and become turgid) and gain mass. By calculating the percentage change in each vegetable piece I will be able to find the concentration of sucrose solution at which the vegetable will gain no mass. Once the isotonic solution is found for each vegetable, its water potential can be found by using a reference graph, which shows the water potential for different concentrations of sucrose.

   The two vegetables I will use will be a potato and a swede. Swedes are considered a sweet root vegetable and so its sucrose concentration is probably quite different from that of a potato because the sucrose gives the vegetable its sweet taste.

Method

To carry out this investigation I will need the following apparatus:

  • Two boiling tube racks
  • Ten boiling tubes
  • 200ml of 1mol sucrose solution
  • A 1ml and 10ml syringe
  • 100ml measuring cylinder
  • One potato and one swede
  • A cork borer (1cm diameter) and knife
  • A ceramic tile

I have chosen to use syringes because they are reliable and will be accurate enough to measure out solutions. By using a cork borer I will be able to eliminate some of the inaccuracy that would normally be encountered if I used a knife only to cut up the vegetable pieces. 200ml of 1mol sucrose solution is all that will be needed to make up all the solutions needed.

Procedure.

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  1. I will fill two boiling tubes each with 1, 0.75, 0.5, 0.25 and 0mol concentrations of sucrose solution (30ml) using the syringes and the measuring cylinder. The boiling tubes should be labelled so that it is clear what concentration of sucrose is contained within them.
  2. 15 potato pieces and 15 swede pieces will be cut using the knife and cork borer. The borer will be able to strips of vegetable and the knife will be used to cut the strips into 2cm lengths.
  3. All the pieces will have their masses recorded and then three pieces of potato ...

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This is a well written report that covers all of the necessary aspects of the investigation. 1. The starting section of the report needs to be broken up with subheadings. 2. The tables of results are well presented. 3. Researched information needs to be referenced and a section for this included. 4. The conclusion is concise and so more analysis could be conducted. 5. The evaluation shows a good understanding of some scientific processes and contains good suggestions. ****