The hypothesis here is that it is the quality of the light, not the quantity of the light that makes a difference, and having a lot more light will not necessarily make photosynthesis occur any faster.
Discussion
With an experiment like this there is always room for error. Measurements taken incorrectly is the biggest problem, because there are multiple steps to be taken each time the light source is moved, and it is very important to ensure that this is being addressed correctly. The quality of the plant and its health could also affect whether it produced photosynthesis rates that are appropriate and generalized for its species, as well. These are variables that can only be controlled to a certain degree and, as such, have to be accounted for.
Materials and Methods
In this experiment, the goal is to measure the rate of photosynthesis that Elodea shoots have when they are exposed to specific light sources and distances. The materials needed are:
Heat filter
Meterstick
Pipette, 1 ml
Plastic tubing, 7 cm lengths
Ring stand
Ring stand test-tube clamps
Scalpel or razor blade
Spot lamp, 300 watt, or fluorescent lamp
Syringe and needle, 5 ml
Test tube
Test-tube rack
Tubing clamp, screw-type
Sodium bicarbonate solution, 2%
Elodea...
The rate of photosynthesis will be studied for each bulb and distance and the number of oxygen bubbles that the Elodea shoot produces will be recorded so that the differences between bulbs can be addressed. This will show whether there is a clear difference in photosynthesis based on quantity of light, quality of light, or both.
Results
The results of the experiments indicate that the rate of photosynthesis with a 100-watt bulb is much higher than the rates with 150-watt bulbs. While the red filter on the 150-watt bulb helped to produce more bubbles in the same length of time, it did not increase bubble production as high as the 100-watt bulb did. Most people would assume that a 150-watt bulb would make more bubbles because of the stronger wattage - and therefore, allegedly, more light - but that was clearly not the case. Instead, the lower wattage light bulb caused a higher level of photosynthesis to occur, as can be seen in the charts below.
Bibliography
Plants and the environment (2003). Ohio State University. http://www.osu.edu/plants/enviroplants.htm
The soil environment. (2004). http://organiclifesytles.tamu.edu/soilbasics/soilenvironment.html
Understanding the environment (1997). Wisconsin Fast Plants. University of Wisconsin-Madison.
