In this experiment, the effects of temperature on rate of photosynthesis in gymnosperms and angiosperms was studied through the use of some samples of gymnosperms and angiosperms, a Carbon Dioxide gas sensor, a computer, some lights and some ice. From the experiment, it was determined that colder temperatures (a colder environment) results in significantly higher rates of photosynthesis in gymnosperms than in angiosperms. Since gymnosperm needles remain green and attached to their tree branches in the winter time while angiosperm leaves turn brown, die and fall off of the branches, it was hypothesized that gymnosperms exhibit significantly higher rates of photosynthesis in colder climates than do angiosperms.

To test this hypothesis, a Carbon Dioxide gas probe was first tested in an empty bottle to make sure that the computer change in CO2 output was zero (to eliminate error). Next, an amount of gymnosperm needles (juniper needles) was weighed and placed in a gas chamber (a.k.a a plastic bottle) at room temperature. The top of the bottle was sealed with a stopper and gas probe. The CO2 gas sensor was plugged into the computer, and two lights were shined onto the sample from two sides. The gymnosperm CO2 output (in ppm/min) was observed for a period of 10 minutes. After 10 minutes, foil was placed over the chamber so that no light could shine through. The change on CO2 was observed for another ten minutes. Next, the foil was taken off and the chamber was placed in a beaker of ice. The lights were turned on once again, and the CO2 output was observed for 10 minutes. After 10 minutes, the chamber was once again covered with foil and CO2 outputs were observed on the computer for 10 minutes.

In order to eliminate a source of error, this same procedure was carried out on another sample of the same type of gymnosperm, only this time, the gymnosperms were initially placed in the ice beaker instead of at room temperature. This would account for error attributed to the time it takes for the plant to warm up or cool down when placed under these conditions.

After this entire procedure was carried out on the gymnosperms, the exact same procedure was carried out on the angiosperms, and the changes in CO2 outputs were observed under each condition. All of these measurements were later converted to ppm/min/g by dividing the computer output of ppm/min by the mass of each sample.

The results of the experiment indicated that the mean rates of photosynthesis for the angiosperm and gymnosperm in a warm climate, which were -1.72 ppm/min/g and -8.358 ppm/min/g, respectively, were not significantly different with a p-value of 0.5811. This p-value is important, because if the gymnosperm rate of photosynthesis was significantly higher in the warm climate than the angiosperm (or vice versa), there would really be no basis for comparison, since the gymnosperm/angiosperm was higher to begin with. In support of the hypothesis, however, the mean rates of photosynthesis for the angiosperm and gymnosperm in the cold climate (which were -.3921 and -2.327 ppm/min/g, respectively) were indeed found to be significantly different; the gymnosperm rate of photosynthesis was significantly greater in cold climate than that of the angiosperm with a p-value of 0.0490.

The results are consistent with the predictions based on the hypothesis, meaning that the hypothesis cannot be rejected. However, the experiment was far from perfect and the results obtained could also be indicating a lot of other factors. There were many sources of error that were not accounted for in the experiment which could have also contributed to the results obtained. One major source of error was the fact that only one type of angiosperm and only one type of gymnosperm were used in the experiment. There were also not enough repetitions of the trials in order to obtain a decent mean. If a variety of types of angiosperms and gymnosperms were used, and if each type underwent the procedures numerous times, more accurate mean rates of photosynthesis could have been obtained. Another source of error that was extremely interesting was the fact that the gymnosperms exhibited no activity (neither CO2 consumption nor respiration) for the first 20 minutes when a light was shown on them. The gymnosperms were acting as if they were asleep! Perhaps the reason that the gymnosperms maintain their green color in the winter is because of the possibility that they may go dormant in the winter time to conserve energy, much like hibernation; the green color is just the pigment being stored in the plant. It is interesting to note that the samples of gymnosperms were both from bushes that were in total shade; the location of the plant sources is another source of error. Another source of error could be the fact that plant hormones were acting along with photosynthesis. Ethylene, for example, is responsible for leaf abscission in angiosperms. Despite all these sources of error, however, the results obtained in this lab support the hypothesis that gymnosperms have significantly higher rates of photosynthesis than do angiosperms in colder climates. These results are different from those on the CABLE webpage; those students found no significant difference between mean rates of photosynthesis in angiosperms and gymnosperms in cold weather. Perhaps they used different types of plants than were used in this experiment, which would support the idea that these results were only obtained for these specific types of plants, and are not repeatable when using other types.