Set up 1) – Normal amount of water; normal amount of oxygen; room temperature
Set up 2) – Normal amount of water; normal amount of oxygen; 4°C (stored in the fridge)
Set up 3) – Normal about of water; no oxygen; room temperature
Set up 4) – Almost no water (2 cm3 per day); normal amount of oxygen; room temperature
Set up No. 1 is the set up with all conditions present for germination. The next three are set ups with one condition missing. When any of the conditions are not present, germination is not expected.
Dependent Variable:
→ Length of seedlings – The rate of germination, in this case the length of the seedlings, will depend on the conditions present for each of the set up. As the conditions for each set up varies, the rate of germination or length of seedling will increase, decrease or stay the same. The length of each seedling will be measured using a vernier caliper, with units in cm.
Controlled Variables:
→ Volume of Water – The volume of water poured per day onto the seeds each day should remain the same, as if the volume changes, the volume of water imbibed by the seed would change, causing the rate of germination to be affected. This in turns affect the length of the seedling. All set ups except Set up 4 should receive the same amount of water per day, which will be maintained at 10cm3. Set up 4 shall receive 2cm3 of water per day. The volume of water will be measured using a 25cm3 syringe.
→ Temperature of surroundings – The temperature of the surroundings must remain the same, as if the temperature changes, the activity of hydrolytic enzymes in the seed embryo will be affected, as enzymes are temperature-sensitive. This will then affect the rate of germination in the seed, which will in turn affect the length of the seedling. All set ups except Set up 2 will be placed in a place with room temperature, with the room temperature ranging from 22°C to 25°C. Set up 2 will be placed in the refrigerator where the temperature will be maintained at 4°C.
→ Amount of oxygen – The amount of oxygen available for germination must remain the same or else the metabolism rate of the seed embryo will be affected, which will in turn affect the rate of germination. This would then lead to the lengths of the seedlings being invalid as more than one condition is not present. All set ups will receive the same amount of oxygen available in the room, except set up 3. Set up 3 will be covered with a layer of oil where oxygen will not get through to the seed.
→ Overall time taken for germination – The amount of time given for each seed to germinate must remain the same, as if the time given for the seeds to germinate varied, some seeds would be able to have more time to grow than the others, which in turns affect the length of the seedlings. The time given for each seed in all the set ups to germinate will be maintained at 1 week.
Apparatus List
Apparatus Setup Diagram
Altogether, there will be four different set ups as mentioned above.
Set Up (1) – Normal Conditions
This set up will have all the conditions needed for the germination of the seed. Like the other set ups, it will have 3 green bean seeds on top of 4 cotton pads. It will receive 10cm3 of water for 7 days, and be placed in an area at room temperature with oxygen. This is so that the seed can germinate as all conditions are present.
Set Up (2) – Unsuitable Temperature
This set up will have all the conditions needed for the germination of the seed except a suitable temperature. Like the other set ups, it will have 3 green bean seeds on top of 4 cotton pads. It will receive 10cm3 of water each day for 7 days, and be placed in the refrigerator with a temperature of 4°C, with oxygen. As the condition for a suitable temperature is not present, the hydrolytic enzymes in the seed would not be able to work as well as when in an optimum temperature; the seed will not be able to germinate.
Set Up (3) – No Oxygen
This set up will have all the conditions needed for the germination of the seed except for a supply of oxygen. Like the other set ups, it will have 3 green bean seeds on top of 4 cotton pads. It will receive 10cm3 of water each day for 7 days, and be placed in an area at room temperature. However, the seeds will be covered in a layer of oil, which will deprive the seeds of the oxygen in the air, hence drowning the green bean seeds. As oxygen is not present, the embryo will be not able to respire in order to provide energy for germination. Without energy, the seed will not be able to germinate.
Set Up (4) – No Water
This set up will have all the conditions needed for the germination of the seed except for a supply of water. Like the other set ups, it will have 3 green bean seeds on top of 4 cotton pads. It will be placed in an area at room temperature with oxygen. However, the seeds will only receive 2cm3 of water each day for 7 days, which will not be sufficient enough for the seeds to germinate. As the supply of water is not sufficient, imbibition will not occur and the metabolism of the seed will remain dormant. Without the metabolic activity of the seed, it will not germinate.
Method
- Lay out all apparatus, clean all of them thoroughly.
- Set up the Petri dishes with 4 cotton pads in each Petri dish. Put three green bean seeds in each Petri dish. Make sure the seeds are of equal distance away from one another.
- Label the set ups 1, 2, 3 and 4. Set up 1) will be the seeds with normal conditions, 2) will be the set up with no suitable temperature, 3) will be the set up with no oxygen and 4) will be the set up with no water.
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Using a 25cm3 syringe, pour 10cm3 of water into Set up 1). Try to make sure each seed gets approximately the same amount of water.
- Repeat step 4 for Set ups 2) and 3).
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Using a 25cm3 syringe, pour 2cm3 of water into Set up 4). Try to make sure each seed gets approximately the same amount of water.
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Using a 50cm3 measuring cylinder, pour 50cm3 of oil into set up 3). The layer of oil should submerge the seeds completely so that there will be no oxygen.
- Place Set up 2) into the refrigerator, which will have a temperature of 4°C. This is so that the seed will be deprived of a suitable temperature.
- Place Set ups 1), 3) and 4) near a window.
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For the next 6 days, using the 25cm3 syringe, pour 10cm3 of water into Set ups 1), 2) and 3). For Set up 4), using the 25cm3 syringe, pour 2cm3 of water.
- At the end of the week, making sure there are no zero errors, measure the length of the germinated seedlings using vernier calipers.
- Tabulate the results.
Results
The table shows the length of seedlings in cm in each of the different set ups after one week.
Analysis of Results
After conducting the experiment, it is found that when all three conditions, presence of water, presence of oxygen and a suitable temperature were present, the seed was able to germinate. However, without any one of these conditions, the seed was unable to germinate, as can be seen from the table of results. Set up (2) was placed in an area with very low temperatures, and was not able to germinate. This meant that without a suitable temperature, the seed would not be able to germinate. Set up (3) was covered with a layer of oil, preventing the seeds from taking in any oxygen from the air, and was unable to germinate as well. This meant that without oxygen, the seed would not be able to germinate. Set up (4) was deprived of a sufficient supply of water, and the seeds were also not able to germinate. Therefore, it can be seen that if any one of these conditions are not present, the seed cannot germinate, and that all conditions must be present for germination to occur.
Conclusion
The results from the experiment showed that only when there was the presence of water, presence of oxygen and a suitable temperature, would the seed germinate. Therefore, I can say that my hypothesis is supported and correct.
This is because:
The seed needs water to undergo imbibition, which would then allow the water to set off the metabolic activity in the seed. The water also dissolves crucial chemicals inside the seed embryo which activates the hydrolytic enzymes. With the hydrolytic enzymes activated, nutrients are then supplied to the seed embryo. Therefore, without water, the seed will not be able to germinate as the embryo will have no nutrients.
The seed also needs oxygen to germinate, as a seed that has yet undergone germination does not have leaves. Leaves contain chlorophyll, which is vital for photosynthesis. The absence of leaves means the absence of chlorophyll, which means that the seed cannot make food to supply energy for itself before it grows leaves. Therefore, oxygen allows the seed to undergo aerobic respiration, providing energy for germination.
Lastly, the seed will also need a suitable temperature before it can germinate. As there are hydrolytic enzymes in the seed that needs to be activated before nutrients can be supplied to the seed, the enzymes will need a suitable temperature to perform its best in. If the temperature is too low or too high, the enzyme activity will be too low or close to none, or the enzyme structure will be denatured, hence not able to even function at all.
Therefore, it is only under all conditions that the seed can germinate.
Reliability
I can say that my experiment is reliable because I relied on three seeds instead of just trying to germinate one seed. This enables my results to be more accurate. There were no problems during the experiment and the lengths of the seedlings were similar to each other. The apparatus used were all reliable and in good condition. The method was as precise as possible, taking note of all the details, especially the apparatus set up diagram, where everything was listed and drawn out. For example, I tried to make sure the amount of water given to each seed was approximately the same so that each seed would receive the same amount of water. In Set up (3), I also made sure that the seeds were fully submerged in the layer of oil so that absolutely no oxygen in the air would be available to the seeds. The method described and explained every step, and provided the results needed. The results analysis were described and explained with as much details as possible, and there were no miscalculation and major errors during the experiment.
Validity
The experiment was valid, as the apparatus used measured everything needed, for example, I used a 25cm3 syringe to measure 2cm3 and 10cm3 of water for the seeds. I also used a 50cm3 measuring cylinder to measure 50cm3 of oil to pour onto the seeds. In addition, a vernier caliper was used to measure the length of the seedlings, which is used to measure lengths and thicknesses up to 0.01cm. It was also checked for any zero errors before it was used. The refrigerator in which Set up (2) was placed in was thermostatically controlled, so the temperature was constant throughout, and there was no need for a use of a thermometer. The method was valid as the dependent and independent variable were measured and results were obtained. The hypothesis was valid as the outcome of the experiment supported it.
Limitations and Improvements
If I could do the experiment again,
→ One or two more seeds could be used so that I could get a better reading on the trends. In addition, I only took the final results, which is the final length of the seedlings. I could have observed the growth of all the seeds closely so that I would be able to further explain and analyze my results.
→ Over the weekend, the seeds were not tended to, so during those two days there was a lack of water for the seeds. I could have brought the set up home with me so that I could tend to them with full attention instead of leaving them in school.
→ During the night and day, the room temperature can vary by 4-5°C. In order to keep the temperature constant in the future, I could put it in a thermostatically controlled room or container. This would ensure that the temperature will remain constant throughout, hence not affecting the seeds’ germination.
