Experiment to Investigate Osmosis in Potatoes

Experiment to Investigate Osmosis in Potatoes

The aim of this experiment is to investigate the movement of water in

and out of plant cells. The cells chosen for study will be taken from

potato tubers. Firstly I will explain what osmosis is. Osmosis is the

passage of water from a region of high water concentration through a

semi permeable membrane to a region of low water concentration. This

definition contains three important statements:

a) It is the passage of water through a semi permeable membrane

b) It is the passage of water from a region of high water

concentration

c) It is the passage of water to a region of low water concentration.

All the above statements are included in the definition, but define

certain aspects of it.

Semi-permeable membranes are very thin layers of material which allow

some things to pass through, but prevent others. A cell membrane is

semi permeable. They allow small molecules like oxygen, water, amino

acids etc. to pass through but will not allow larger molecules like

sucrose, starch, protein etc. through. A region of high concentration

of water is either a very dilute solution of something like sucrose or

pure water. In each case there is a lot of water: a high concentration

of water. A region of low water concentration is the opposite of the

above, i.e. a very high concentration of sucrose solution: a low water

concentration.

The water content of plants varies depending on environmental

conditions. In Land plants this water plays a vital role in the

support of tissues and the transport of materials around the organism.

Lack of water leads to wilting and eventually death. Water is mainly

absorbed through the roots, which are covered in specially adapted

root hair cells, with large surface areas and thin cell walls to aid

absorption. It is drawn up the plant through xylem vessels by a pull

resulting from the evaporation of water through the stomata on the

leaves. This evaporation is called transpiration and the xylem flow

resulting is called the transpiration stream. Soluble food substances

formed during photosynthesis are transported around the plant in the

phloem tubes. This movement of water through the plant in the xylem

vessels or phloem tubes is similar to the flow of blood in humans as

it transports soluble mineral salts, nutrients and auxins, (plant

hormones), from p...

... middle of paper ...

... have been what

caused the anomalous results, as it was lighter that the best fit line

i.e. some water may have been lost through harder drying, or squeezing

during the drying process. If some of the water evaporated overnight,

it would have incresed the molarity of the solutions, thus making the

results innaccurate. This could be combatted by putting a bung in the

top of the test tubes to stop the evaporation and keeping the sugar

slution concentrations the same. To improve the accuracy of the

results I would include more concentrations to find the point of

plasmolysis as in my experiment, I did not get to the point of

plasmolysis in my experiment, so if I was to extend this experiment, I

would investigte a wider rage of concentrations to investigate furthur

and increase accuracy. I would also increase the repetitions to 5 per

molarity and increase the molarity to try and find the point of

plasmolysis. I could also decrease the range between each molarity

(every 0.05 for example) to try and find the exact concentration of

the potato cells where there is not net gain. This investigation was

succesful but could still be made more accurate by some of the above

ways.