The procedure was repeated for a dark area. All the while the test tube containing the elodea was immersed in a beaker of water to ensure constant temperature conditions.
Observation:
The rate of release of bubbles, this oxygen released, was greater (in mmmin-1) in the straight than in a dark area.
Results:
Table showing the distance (mm) moved of fluid in the tube with time (min) in light and dark condition
GRAPH SHOWING DISTANCE OF FLUID MOVED IN TUBE WITH TIME(min)
Discussion:
Photosynthesis consists of interconnected reactions. Thus the rate of this process is dependent upon the slowest reaction, which is in turn dependent on certain factors/condition. Such factors may be concentration of CO2, temperature and light intensity. In the experiment both concentration of CO2 and temperature were kept constant, thus the limiting factor would be light intensity.
The light experiment was done at noon with maximum sunlight, since CO2 was added to the test tube in the form of hydrogen bicarbonate CO2 was not a limiting factor, nor was the temperature since the test tube was immersed in a beaker of H20. Since light, Co2 and temperature were not limiting the rate of oxygen evolved/distance of fluid moved/ rate of photosynthesis continued to increase, thus a linear graph was obtained in high light intensity. This increase would continue until either light intensity started to decrease or the CO2 within the test tube was used up, the graph would have then leveled off with the decrease in CO2 concentration. On the other hand the Elodea in the dark (previously illuminated in pond) having both constant temperature and steady supply of CO2, still saw a decrease in the rate of oxygen evolved/ distance of fluid moved/ rate of photosynthesis, since light intensity was low and was therefore the limiting factor, lowering the rate of a particular reaction of photosynthesis.
Conclusion:
Since the rate of oxygen released increased with the increase of light intensity it may be concluded that the rate photosynthesis also increases (since the rate of photosynthesis is proportional to th release of oxygen) with increased light intensity.
by
JamminInJamica (student)
