Modifications to method during practical performance
- Instead of doing 0ml, 5ml, 10ml and 15ml, I decided to do 0ml, 5ml, 10ml and 20ml.
I decided to do 20ml instead of 15ml as 10ml and 15ml were extremely similar.
- Instead of putting 3 green beans per dish I put 4 per dish.
Three beans per dish was probably too little; there was plenty of space left and additional beans may supplement any failure eg. one of the other beans fail to germinate.
- I measured the length after one day and after two days, instead of just measuring the root on the second day
This would enable me to work out the rate of germination as well.
- I formed a square with the green beans and I added orientation.
This would let me measure the length of the same bean on both days ie. No confusion.
Results
After 1 day (Length of root is measured)
After 2 days (Length of root is measured)
Conclusion: There really isn’t an optimum amount of water to germinate green beans; the more the better. As proven by the results, the control (with no water) did not germinate at all, and the more water provided, the longer the root of the germination plant. With 5ml of water, the average root grew 0.875mm after two days, but with 10ml, the length of the average root is more than doubled (13.625mm).
The seeds in Petri dish 2 germinated markedly slower, and even after two days the average length of root did not even exceed the average length posed by the seeds in petri dish 3 after one day. In fact, one of the seeds in Petri dish 2 failed to even germinate at all.
Although the more water the better, there seems to be a more efficient amount of water that can be used; this may be important for agricultural reasons. As can be observed from the above table, the bean that grew the longest root was one that belonged to the Petri dish with 10ml of water, even though Petri dish 4 had twice the amount of water as Petri dish 3. Also, on the first day the seeds in Petri dishes 3 and 4 germinated at almost the same rate.
Evaluation: Below are some things that could be improved and suggestions for improvement are provided:
- Because water was simply measured and poured in, and because the green beans were spread out, not all the beans received the same amount of water.
This situation could be improved by taking the total volume of water for the particular Petri dish and divide it equally for each seed eg. For the 20ml Petri dish measure out 5ml of water for each green bean and pour it directly on each seed. This overlooking of a procedure also probably resulted in a seed in Petri dish 3 growing to a stunning 31mm.
- The Petri dishes were sealed by simply attaching cellophane tape perpendicularly to the opening, meaning the Petri dishes were possibly not completely sealed.
This could have been a problem as the dish would
already be full of cotton wool, and cellophane tape is easily stretched. This could mean that for some of the Petri dishes internal conditions were not constant throughout the experiment. This problem could actually be easily solved; instead of attaching the cellophane tape perpendicularly, attach it parallel to the opening all around the dish. Although this could mean more tape being used up, this does ensure that internal conditions for ALL Petri dishes are constant throughout the whole experiment. Diagrams of this are shown on the right:
- Amounts of cotton wool used for each Petri dish were not equal.
Although this is quite a minor problem, it can easily be solved by first weighing the amount of cotton wool put into each dish and making sure that the weight of cotton wool in all three Petri dishes are the same.
- During the two days over which the experiment was performed over, the seeds could have been displaced to an area with completely different conditions.
This problem probably resulted in a seed from Petri dish 2 that failed to germinate even after two days. A method to solve this is possibly to nip off bits of cotton wool so a little hole for each seed is effectively made.
Below are some things that were implemented well:
- Orientation labels were used.
This enabled me to measure the same green bean on both days.
- Petri dishes were sealed properly
This would ensure that many variables are controlled eg. temperature, CO2 levels, moisture etc.
- Four beans were used for each Petri dish.
This ensures variable control (ie. Number of seeds) and four seeds is manageable yet informative.
