Hypothesis: I believe the vascular tissues tested with the sclerenchyma will have a much higher tensile strength in comparison to the vascular tissues without the sclerenchyma. The sclerenchyma is very much lignified. This gives the plant more support meaning it takes a lot more force to actually cause the tissues to break. The vascular bundles being tested without the sclerenchyma will easily snap because the tissues only contain a minor amount of lignin and a lot of packing tissue which is not as tough as the sclerenchyma.
Key equipment: I will be using two clamps to hold the bull dog clips and tissues in place; two bulldog clips will be held by the clamps. I will then need to attach two rubber tubes approximately 5cm in length to the bulldog clip so I can place my vascular tissue between them for a good grip. When the vascular tissue is in place I will need a mass holder and masses to hang off the centre of the tissues until the bundles break.
Safety:
Here is a risk assessment table for the hazards associated with this experiment.
(0-5 = Safe experiment, 5-10 = Take Care, 10-15 = Teacher controlled, 15+ = Not safe)
Results
Before we started the actual experiment we did a trail testing to estimate how many grams of mass we would need to aim our experiment towards.
Here are the results from the trail:
After having an estimate to the masses we should for the experiment we carried it out, in my group with I used 10g masses for vascular tissues not containing sclerenchyma. Here are my own results:
The range for my result was (180-80) 100. Here are the class results for groups with and without sclerenchyma.
The result highlighted is an anomalous result and has not been included in the average. The next table shows the same results converted into the amount of force needed to break the vascular bundles.
I have also drawn out bar graphs containing error bars and averages attached.
Conclusion
From my results I can see there is a definite increase in force and mass needed to break the vascular bundles attached to the sclerenchyma. We can see this because the result bars for the sclerenchyma bundles was significantly higher up the y axis in comparison to the vascular bundles without the sclerenchyma. These results help me conclude that my hypothesis was correct and the added sclerenchyma really does increase the strength of the vascular bundles due to their lignified walls giving the plant structure more strength. There is a clear increase in the force and mass needed to break the structures shown on my graphs.
Evaluation
On my graph there were wider error bars for my results with sclerenchyma and narrow error bars for results without the sclerenchyma the wider error bars show there is more uncertainty in the measurements and errors may have occurred making the results slightly unreliable and invalid. However, the narrow error bars show reliability and little uncertainty in the results.
The measurements take were not taken with too much accuracy because there were a number of things we could not control. For example we could not control the length of vascular tissue actually clamped, because some of the length of the tissue was used in attaching it to the experiment. Also, the tissues kept on slipping out of the bulldog clips so we were unable to test the actual strength of the material, but only the amount it can hold in the clip, it was hard to tell whether it was slipping out or if it was actually snapping. There could have still been traces of sclerenchyma left on the vascular tissue I was testing that could have altered some of the results slightly. This may have been the case for test 5 in my group results where the results were significantly higher than the other results. Random errors would have included the times where the vascular tissue had slipped out of the clips and had to be re-used, this would have reduced the strength of the tissue. We did not have time to improve our methods or carry out repeats. The results were validated by the whole class although there may have been some variations in the range most of the results were still following the same pattern and trends shown and expected in the hypothesis. This experiment in my opinion was valid and reliable in proving my hypothesis correct.
If I could extend or improve this experiment I think I would find a better method to holding the vascular tissue that took up less of the tissue, for example using just one bull dog clip and holding it up right. Maybe hanging weights off it this way would be a better idea. Making more repeats maybe 10 for each one would give a better average. If I was to extent this experiment I could try to test how the length of the plant affects the tensile strength of the overall vascular tissue and change my independent variable to length of plant tissue. Maybe still keep the variables from this experiment but extend my overall result and testing. More time would also be needed in consideration.