Introduction
The null hypothesis for the experiment was that oxygen production is the same in both plants while the alternative hypothesis was that oxygen production and thus the rate of photosynthesis is higher in Ceratophyllum than in Cabomba due to its efficiency in carbon dioxide utilization (Kitaya, Murakami, & Takeuchi, 2003).
Materials and Methods
Experimental Design
The research question to be answered in the experiment was whether there is rate difference, in oxygen production, in oxygen production between Ceratophyllum and Cabomba. It was predicted that each of the plants would have different oxygen production rates. The dependent variable was the rate in oxygen production while organism was the independent variable. The treatments that related to independent variable were 6 grams for Ceratophyllum for treatment one and 6 grams of Cabomba for treatment two. Water was used as the control in the experiment.
The experiment had two treatments, treatment 1 and 2 with each treatment having two experimental tubes that acted as the replicates. In treatment 1, experimental tube number 1 contained 6 grams of Ceratophyllum and the tube filled with the appropriate amount of pond water. In the experimental tube number 2, 6 grams of Ceratophyllum were added and the tube filled with the appropriate amount of pond water. In treatment 2, experimental tube 1 contained 6 grams of Cabomba and filled with the appropriate amount of pond water. Experimental tube 2 contained 6 grams of Cabomba and filled with the appropriate amount of pond water. Control tubes were filled with pond water.
Experimental Apparatus
The Closed Manometric System
This is a closed system that permits the researcher to monitor changes in pressure that are the result of a gas such as oxygen gas produced in the experiment. The system was used to measure oxygen produced by the aquatic plants. The manometer had the following components: a tank, test tube rank, three glass tubes, three stoppers assemblies, each consisting of a stopper, syringe and pipette, plastic Pasteur pipette, blue water that acted as the fluid indicator in the manometer system, and conditioned water for glass tubes.
Organisms
Two organisms were used in the experiment Ceratophyllum and Cabomba. Six grams of each of these organisms were weighed making sure that the amount of water on the weigh scale was minimal.
Glass Tube Contents-Experimental and Control Tubes
Two glass tubes served as experimental tubes containing organisms while one tube served as the control tube containing mo organism. In the experimental tubes, 6 grams of each organism were added, and the tubes filled with specified water that was conditioned for all the tubes. The control tube contained all the contents that were in the experimental tube except the organism.
Closing the Manometer System
Each syringe plunger was set to approximately 2 on each syringe and stopper used to stopper each glass tube on syringe assembly. A small drop of blue water or fluid indicator was added to the end of each pipette using the plastic Pasteur pipette. The syringe was used to pull water droplet into the main body of the pipette. It was ensured that the droplet was between 3mm and 5mm in length, and any larger droplet was pushed out of the pipette inserted again. Syringe was used to adjust water droplets to a starting position making sure that each pipette was in a horizontal position. Care was taken not to bump the manometer systems to avoid alteration of a water droplet position.
Equilibration
After the setup was complete, each system was allowed to stand for 15 minutes to permit time for the organisms to equilibrate to the variable. During this time, the water droplet or fluid indicator in each pipette was seen slowly moving away from the direction of the stopper as oxygen was being produced. In cases where water droplet did not move or moved in the opposite direction, the system was rechecked to make sure there were no leakages. No movement was expected in the control tube.
Measurements
Using the syringe, the water droplet or fluid indicator was reset to a pre-determined value on the pipette in each of the systems. Timing was started, and pipette reading was taken every two minutes. Reading of the pipette was done from the same side of the water droplet without alternating. The change in position of the water droplet was caused by the oxygen produced by the organisms. Care was taken to avoid the water droplet from moving towards the stopper end of the pipette. Time and pipette readings were recorded in a table. During each two minute wait, the cumulative oxygen production that has occurred in each system was calculated. The measurements were taken every 2 minutes for 16 minutes. The measurements of the cumulative oxygen produced for each tube were added to the appropriate class data sheet.
After the experiment, all the components of the experimental apparatus were returned to their original location and all the water wiped to leave the station clean and dry.
Results
Treatment 1
The cumulative amount of oxygen that was produced in treatment 1 (Ceratophyllum) were measured and recorded in Table 1.
Calculations
Photosynthetic Rate
The photosynthetic rate that was associated with each treatment 1 experimental and control tubes was calculated. A graph of cumulative oxygen produced in mL against time in hours was plotted as shown in Figure 1 below.
The gradients of the slopes were obtained from the equation of the line of best fit. For the organisms in group 1 tube 1, the slope had a gradient of 0.1375mL of oxygen produced per hour. The slope was divided by the mass of the organisms introduced in the experimental tube of 6.07 grams.
Photosynthetic rate=0.1375ml/hour6.07 g
This gives 0.0226ml of oxygen produced per hour per gram of Ceratophyllum
For the organisms in group 1 tube 2, the slope had a gradient of 0.3425mL of oxygen produced per hour. The slope was divided by the mass of the organisms introduced in the experimental tube of 6.05 grams.
Photosynthetic rate=0.3425ml/hour6.05 g
This gives 0.325ml of oxygen produced per hour per gram of Ceratophyllum
For the organisms in group 1 control tube, although there was no organism that was added, the slope had a gradient of 0.0625mL of oxygen produced per hour.
For the organisms in group 2 tube 1, the slope had a gradient of 0.05mL of oxygen produced per hour. The slope was divided by the mass of the organisms introduced in the experimental tube of 6 grams.
Photosynthetic rate=0.05ml/hour6 g
This gives 0.008ml of oxygen produced per hour per gram of Ceratophyllum
For the organisms in group 2 tube 2, the slope had a gradient of 0.105mL of oxygen produced per hour. The slope was divided by the mass of the organisms introduced in the experimental tube of 6 grams.
Photosynthetic rate=0.105ml/hour6 g
This gives 0.0175ml of oxygen produced per hour per gram of Ceratophyllum.
For the organisms in control tube, in group 2, although there was no organism that was added, the slope had a gradient of 0.0225mL of oxygen produced per hour.
For the organisms in group 3 tube 1, the slope had a gradient of 1mL of oxygen produced per hour. The slope was divided by the mass of the organisms introduced in the experimental tube of 6 grams.
Photosynthetic rate=1ml/hour6 g
This gives 0.167ml of oxygen produced per hour per gram of Ceratophyllum
For the organisms in group 3 tube 2, the slope had a gradient of 1.9mL of oxygen produced per hour. The slope was divided by the mass of the organisms introduced in the experimental tube of 6 grams.
Photosynthetic rate=1.9ml/hour6 g
This gives 0.32ml of oxygen produced per hr per gram of Ceratophyllum
For the organisms in control tube, in group 3, although there was no organism that was added, the slope had a gradient of 0.2mL of oxygen produced per hour.
For the organisms in group 4 tube 1, the slope had a gradient of 0.45mL of oxygen produced per hour. The slope was divided by the mass of the organisms introduced in the experimental tube of 6 grams.
Photosynthetic rate=0.45mlhour6 g
This gives 0.075ml of oxygen produced per hr per gram of Ceratophyllum
For the organisms in group 4 tube 2, the slope had a gradient of 0.9mL of oxygen produced per hour. The slope was divided by the mass of the organisms introduced in the experimental tube of 6.05 grams.
Photosynthetic rate=0.9ml/hour6.05 g
This gives 0.149ml of oxygen produced per hr per gram of Ceratophyllum
For the organisms in control tube, in group 4, the slope had a gradient of 0mL of oxygen produced per hour.
For the organisms in group 5 tube 1, the slope had a gradient of 0.65mL of oxygen produced per hour. The slope was divided by the mass of the organisms introduced in the experimental tube of 6 grams.
Photosynthetic rate=0.65ml/hour6 g
This gives 0.108ml of oxygen produced per hr per gram of Ceratophyllum
For the organisms in group 5 tube 2, the slope had a gradient of 0.85mL of oxygen produced per hour. The slope was divided by the mass of the organisms introduced in the experimental tube of 6 grams.
Photosynthetic rate=0.85 ml/hour6 g
This gives 0.142 ml of oxygen produced per hr per gram of Ceratophyllum
For the organisms in group 5 control tube, the slope had a gradient of 0mL of oxygen produced per hour. Since no organism was introduced, there was no photosynthetic rate that was observed.
Treatment 2
The cumulative amount of oxygen that was produced in treatment 2 (Cabomba) were measured and recorded in Table 2.
Calculations
Photosynthetic Rate
The photosynthetic rate that was associated with each treatment 2 experimental and control tubes was calculated. A graph of cumulative oxygen produced in mL against time in hours was plotted as shown in Figure 2 below. The graph of mean oxygen production per hour in the different treatments and their associated control is shown in Figure 3 below.
The gradients of the slopes were obtained from the equation of the line of best fit. For the organisms in group 1 tube 1, the slope had a gradient of 1.5mL of oxygen produced per hour. The slope was divided by the mass of the organisms introduced in the experimental tube of 6 grams.
Photosynthetic rate=1.5ml/hour6 g
This gives 0.25ml of oxygen produced per hr per gram of Cabomba
For the organisms in group 1 tube 2, the slope had a gradient of 1.95mL of oxygen produced per hour. The slope was divided by the mass of the organisms introduced in the experimental tube of 6 grams.
Photosynthetic rate=1.95ml/hour6 g
This gives 0.325ml of oxygen produced per hr per gram of Cabomba
For the organisms in group 1 control tube, the slope had a gradient of 0mL of oxygen produced per hour. Since no organism was introduced, there was no photosynthetic rate that was observed.
For the organisms in group 2 tube 1, the slope had a gradient of 3.8mL of oxygen produced per hour. The slope was divided by the mass of the organisms introduced in the experimental tube of 5.92 grams.
Photosynthetic rate=3.8ml/hour5.92 g
This gives 0.64ml of oxygen produced per hr per gram of Cabomba
For the organisms in group 2 tube 2, the slope had a gradient of 1.5mL of oxygen produced per hour. The slope was divided by the mass of the organisms introduced in the experimental tube of 6.02 grams.
Photosynthetic rate=1.5ml/hour6.02 g
This gives 0.25ml of oxygen produced per hr per gram of Cabomba.
For the organisms in group 2 control tube, although there was no organism that was added, the slope had a gradient of 0.15mL of oxygen produced per hour.
For the organisms in group 3 tube 1, the slope had a gradient of 3.75mL of oxygen produced per hour. The slope was divided by the mass of the organisms introduced in the experimental tube of 5.99 grams.
Photosynthetic rate=3.75ml/hour5.99 g
This gives 0.626ml of oxygen produced per hr per gram of Cabomba
For the organisms in group 3 tube 2, the slope had a gradient of 4.15mL of oxygen produced per hour. The slope was divided by the mass of the organisms introduced in the experimental tube of 6.02 grams.
Photosynthetic rate=4.15ml/hour6.02 g
This gives 0.69ml of oxygen produced per hr per gram of Cabomba
For the organisms in control tube, in group 3, although there was no organism that was added, the slope had a gradient of 0.2mL of oxygen produced per hour.
For the organisms in group 4 tube 1, the slope had a gradient of 3.125mL of oxygen produced per hour. The slope was divided by the mass of the organisms introduced in the experimental tube of 5.99 grams.
Photosynthetic rate=3.125ml/hour5.99 g
This gives 0.52ml of oxygen produced per hr per gram of Cabomba
For the organisms in group 4 tube 2, the slope had a gradient of 2.575mL of oxygen produced per hour. The slope was divided by the mass of the organisms introduced in the experimental tube of 6.02 grams.
Photosynthetic rate=2.575ml/hour6.02 g
This gives 0.428ml of oxygen produced per hr per gram of Cabomba
For the organisms in control tube, in group 4, although there was no organism that was added, the slope had a gradient of 0.132mL of oxygen produced per hour.
For the organisms in group 5 tube 1, the slope had a gradient of 2 mL of oxygen produced per hour. The slope was divided by the mass of the organisms introduced in the experimental tube of 5.93 grams.
Photosynthetic rate=2ml/hour5.93 g
This gives 0.337ml of oxygen produced per hr per gram of Cabomba
For the organisms in group 5 tube 2, the slope had a gradient of 3.2mL of oxygen produced per hour. The slope was divided by the mass of the organisms introduced in the experimental tube of 5.87 grams.
Photosynthetic rate=3.2 ml/hour5.87 g
This gives 0.545ml of oxygen produced per hr per gram of Cabomba
For the organisms in group 5 control tube, the slope had a gradient of 0mL of oxygen produced per hour. Since no organism was introduced, there was no photosynthetic rate that was observed.
A t-test was done to compare the photosynthetic rate by Cabomba with that of Ceratophyllum. The test showed that there was a statistical significant difference with Ceratophyllum showing a higher photosynthetic rate than Cabomba.
Tables and Figures
Figure 3: Mean oxygen production per hour in the different treatments and their associated control
Discussion
Photosynthesis is the process through which light energy is captured and used to make food in plants. The rate of photosynthesis is usually affected by factors such as the amount of light reaching the plant, temperature and the amount of carbon dioxide available. Increase in light intensity, temperature and carbon dioxide increase the rate of photosynthesis. Low amounts of these factors also reduce the rate at which photosynthesis takes place (Mishra, 2004).
Cabomba refers to a group of submersed aquatic plants. The plants belong to the family Cabombaceae. The plant is usually preferred by most aquarists as a plant that oxygenates fish tanks and is also used as an ornamental plant. On the other hand, Ceratophyllum are those submerged plants that are mainly found in ponds, quiet streams, and marshes. The plants are also known as hornworts and belong to the order ceratophyllales (Simpson, 2011).
The current study aimed to determine the rate of photosynthesis in Cabomba and Ceratophyllum submerged plants. From the results, Cabomba has a higher rate of photosynthesis compared to Ceratophyllum organism. There was a significant difference between the rates of photosynthesis of the two organisms. This data does not support the null hypothesis that was set. Additionally a previous study that compared the rate of these organisms reported a lower photosynthetic rate in Cabomba than in Ceratophyllum. This study did not support these findings. The high rate may be contributed to the efficiency that the plant has in using carbon dioxide (Kitaya, Murakami, & Takeuchi, 2003).
In conclusion, the two organisms tested did not have the same rate of photosynthesis with Cabomba having the highest photosynthetic rate.
Reference List
Kitaya, Y. O., Murakami, K., & Takeuchi, T. (2003). Effects of CO2 concentration and light intensity on photosynthesis of a rootless submerged plant, Ceratophyllum demersum L., used for aquatic food production in bioregenerative life support systems. Advances in Space Research, 31(7), 1743-1749.
Mishra, S. (2004). Photosynthesis in Plants. Grand Rapids: Discovery Publishing House.
Simpson, M. G. (2011). Plant Systematics. Waltham: Academic Press.
