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Elodea Plant Lab

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Introduction

Aquatic Photosynthesis of Elodea Leaves Lab Design Problem: What is the effect of temperature (warm, cool, room temperature) on the rate of photosynthesis in Elodea leaves measured by the levels of dissolved oxygen in the flask solutions? Hypothesis: If temperature is related to the rate of photosynthesis (levels of dissolved oxygen) then increasing the temperate will increase the rate of photosynthesis up to an optimal temperature. Variables: Independent: temperature of the water bath which the Elodea plant is immersed in Dependent: the rate of photosynthesis measured by the level of oxygen dissolved in the flask solution Constants: Relative size of the Elodea leaf, relative surface area of the Elodea leaves, (around 3 cm each), volume of water in all beakers, amounts of light exposure to the plants, and type of light source. Method: Materials: Light Source Elodea. Keep this warm and illuminated before you use it, 3 small flasks, 10g/L sodium bicarbonate (NaHCO3) solution, oxygen sensor Lab Quest data logger. Graduated cylinder Hot Plate 3 Large beaker (1 for warm water, 1 for cool water, 1 room temp) ...read more.

Middle

Heat some tap water in the large beaker until it reaches the desired temperature (I suggest 25 C). Maintain the water at this temperature. Be sure to record all relevant data. 5) Cool some tap water with ice to your desired temperature. Maintain this temperature throughout the experiment by adding ice as needed. 6) Locate your datalogger and oxygen sensor. Plug in and turn on the LabQuest datalogger. 7) Obtain 3 flasks 8) Obtain three small (2 -3 cm long) sprigs of Elodea of similar appearance, of equal size and with equal leaf surface areas. Add each one to its own flask. 9) Add equal amounts of sodium bicarbonate solution to each flask (make sure that you add enough to cover the Elodea sprig). Note: Sodium bicarbonate adds CO2 to the water, which aids in photosynthesis. 10) Place one flask in the warm water bath, one in the cold water and leave one out at room temperature. 11) Place all of the flasks under the light source so that they receive equal amounts of light. ...read more.

Conclusion

Thermometer: �0.5 (Degrees Celsius) Data Processing Sample Calculation: Presentation of Processed Data: Graphs: Conclusion/Evaluation Conclusion: Based on my data collection and processed calculations, my hypothesis was correct in the sense that temperature is related to the rate of photosynthesis (levels of dissolved oxygen) and thus, increasing the temperate increased the rate of photosynthesis up to an optimal temperature. According to my previous knowledge of limiting factors on photosynthesis, I would have expected both hot water and cold water rates of photosynthesis to be lower than that of the room temperature as when looking at a typical graph of the effect of temperature on the rate of photosynthesis we see a bell shaped curve in which too cold of a temperature as well as too hot of a temperature will inhibit/denature photosynthesis, thought a moderate temperature will be optimal with a high rate of photosynthesis. One possible explanation for the higher rate of photosynthesis of the hot water bath could be the fact that we had not yet reached the optimal temperature before it starts to denature and decrease in the rate of photosynthesis. ...read more.

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Here's what a teacher thought of this essay


Overall this is a fairly poor piece of work. The student has completed the experiment and collected data, but has made a fundamental error of understanding and so drawn the wrong conclusions. This demonstrates how important it is to pay attention to what is actually being plotted on a graph. I would also expect an undergraduate to be able to elaborate on null and alternative hypotheses.In a first year practical this write up might get 2/5, as the demonstrators should have cleared up the misunderstanding.

Marked by teacher Rebecca Lewis 02/05/2012

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