Osmosis in Plant Cells

Observation of Osmosis in Plant Cells

Observation of osmosis in plant cells by using potato strips

Adapted from http://www.practicalbiology.org/areas/intermediate/exchange-of-materials/osmosis/investigating-the-effect-of-concentration-of-blackcurrant-squash-on-osmosis-in-chipped-potatoes,44,EXP.html

In this experiment, three weights as well as three lengths have been recorded for each of the three potatoes in the three substances; distilled water, sodium chloride water solution and glucose solution, for each of the three time periods; initial length and weight, after 40 minutes and after 60 minutes.

Tables 1-3; Length of potatoes in each of the indicated solutions over the 0, 40 and 60 minute's period of time, with an error of 0.1, due to our measuring the length with a ruler.

Table 1; Length of potato strips for distilled water, for each of the indicated time samplings

dH2O

0min

40mins

60mins

1st potato [cm error]

4.5 cm

4.7 cm

4.8 cm

2nd potato [cm error]

4.5 cm

5 cm

5 cm

3rd potato [cm error]

4.5 cm

4.7 cm

4.8 cm

Table 2; Length of potato strips for sodium chloride, for each of the indicated time samplings

NaCl

0min

40mins

60mins

1st potato [cm error]

4 cm

4 cm

3.8 cm

2nd potato [cm error]

4 cm

3.8 cm

3.4 cm

3rd potato [cm error]

4 cm

4 cm

3.8 cm

Table 3; Length of potato strips for glucose, for each of the indicated time samplings

Glucose

0min

40mins

60mins

1st potato [cm error]

4 cm

3.8 cm

3.7 cm

2nd potato [cm error]

4 cm

4 cm

3.3 cm

3rd potato [cm error]

4 cm

3.2 cm

3.1 cm

Tables 4-6; Weight of potatoes in each of the indicated solutions over the 0, 40 and 60 minute's period of time, with an error of 0.1, due to our measuring the potatoes with an electronic balance correct to two significant figures.

Table 4; Weight of potato strips for distilled water, for each of the indicated time samplings

dH2O

0min

40mins

60mins

1st potato [g error]

5.5 g

6 g

6.1 g

2nd potato [g error]

5.2 g

5.7 g

5.8 g

3rd potato [g error]

4.9 g

5.4 g

5.5 g

Table 5; Weight of potato strips for sodium chloride, for each of the indicated time samplings

NaCl

0min

40mins

60mins

1st potato [g error]

4.9 g

3.8 g

3.4 g

2nd potato [g error]

4.6 g

3.6 g

3.2 g

3rd potato [g error]

5.6 g

4.7 g

4.3 g

Table 6; Weight of potato strips for glucose, for each of the indicated time samplings

Glucose

0min

40mins

60mins

1st potato [g error]

6.1 g

5.2 g

5 g

2nd potato [g error]

4.4 g

4.9 g

4.7 g

3rd potato [g error]

5.8 g

3.6 g

3.4 g

Observations;

I. All potatoes had to be fully covered by the solution for the measurement to be ideal.

II. Human errors occurred as we cut the potatoes by hand and not with the help of any equipment.

III. The electrical balance had to be cleaned every time we measured for as to avoid any false measurements.

IV. The thinner or bigger in surface the potato was, the quicker the reaction occurred.

By using the results of the experiment, the following graphs occur, so that there is a better understanding of the situation.

Graph 1; Length of potato strips for dH2O for each of the trials

Observations;

I. The trials vary from one another quite a lot indicating the existence of factors affecting the results other than the independent ones

II. Values generally indicate an increase in length as time goes by.

Graph 2; Length of potato strips for sodium chloride for each of the trials

Observations;

I. Length shows little change as time goes by.

II. The trials are very close to one another with only little deviation from the general tendency.

Graph 3; Length of potato strips for glucose for each of the trials

Observations;

I. Values show a tendency for potato strips to become shorter in length as time goes by

II. The above general tendency is supported by the trials since the values do not deviate a lot from one another.

Graph 4; Weight of potato strips for distilled water for each of the trials

Observations;

I. Values indicate a tendency for weight of the potato strips to increase as time passes by.

II. Trials are close to one another yet indicating the case of error too.

Graph 5; Weight of potato strips for sodium chloride for each of the trials

Observations;

I. Values clearly indicate a drop in weight as time passes.

II. In general, while the two trials agree with one another, the third one varies quite a lot. This portrays the need for many measurements to be taken from trials so as to secure safer results.

Graph 6; Weight of potato strips for glucose for each of the trials

Observations;

I. As time passes, the weight of the potato strips exposed to glucose looses weight.

II. Different trials indicate different rates at which this is done though they all comply to the above statement.

CONCLUSION and EVALUATION

As it is already known, osmosis is the passive movement of water molecules from a region of lower solute concentration to a region of higher solute concentration, across a partially permeable membrane. According to this fact and in relation to our prior hypothesis, water should be transferred from the distilled water solution to the potatoes, thus causing them to increase both in length and weight, in contrast to the other two solutions, where water would transfer from the potatoes to the NaCl and glucose solutions, causing them to decrease both in length and weight. This can be illustrated through our tables and graphs, showing the increase or decrease in length and weight respectively.

As the results of this experiment confirm the general fact met above, the experiment can be characterised as reliable. Nevertheless, errors might have occurred due to various reasons;

I. Not all potatoes of the same group had the same size, surface area, or weight since they were cut bare-handed, without any technological support.

II. The electrical balance and ruler where not very precise, thus leaving the possibility of an error to have occurred (+- 0.1 g and +- 0.1 cm respectively).

III. It was very hard to eliminate the possibility of miss-weighting the potato due to the solution which is still there and have not dried up completely.

Ways to improve the method:

I. Use a device to cut the potatoes in even parts

II. Use a specified technological device to measure the potato's length and weight

III. Allow more time for the potatoes to react, especially when they are quite thick.

Future Work:

The same procedure could be applied to a future experiment which wishes to investigate the rate at which osmosis is achieved either in the environment or a controlled situation as is in the laboratory, and even the rate at which osmosis is achieved in different solutions.

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