Science Experiment Help!

Question

For Bio, we're supposed to design an experiment to measure how the rate of photosynthesis is affected by the initial levels of CO2 (hydrogen carbonate) and we're supposed to test this by using the Elodea Method, then sketch a graph to show the results.

I am seriously clueless, and totally out of ideas, so i really really would appreciate help on creating on a method.

Thanks so much!

Answer 1

For your different trials, use the same mass of elodea plants, the same volume of water, but vary how much sodium bicarbonate (baking soda) you put in the water.  Weigh out different amounts for your treatments and be sure to have one where you add none.

Put your plant and water (with the sodium bicarbonate dissolved) into large test tubes (make sure the water is all the same temperature), and then use a rubber stopper with a bent glass tube coming out of the top.  (One end of the glass tube should be in the water inside the . . . oh s***w it, I can't explain it well enough, just look at a photo at: http://dbs.umt.edu/courses/biol101S04/la...

Anyway, then expose them to the same light and use a marker to mark how far the water moves along the glass tube after each minute.  Then use the distance the water moved to calculate a rate of photosynthesis.  (By the way, the water moves because the plant is taking dissolved bicarbonate out of the water and producing gaseous oxygen, which has a greater volume and therefore pressurizes the contents of the test tube.)