Hi everyone, I searched google for the photosyntesis + light and discovered this nice forum. As I have understood red and blue light is best for the photosynthesis. The result of a good photosynthesis is that it's produced much oxygen, right? Well, here comes my confusion and the reason I write this thread. Yesterday I made the classical lab about the photosynthesis with the Elodea densa. I cut of a stalk of 10 cm and placed it upside down in a cup with water and 1 g of bicarbonate (to add some carbon dioxide). I had a 40 W lamp and put a green plastic filter over its shield (to get green light) and the placed the cup with its content 10 cm away from the light bulb. I let the cup stand like that for three minutes to adapt to the climate. After these three minutes I counted the bubbles (the oxygen = end product of the photosynthesis) which came out from the plant’s stalk for another three minutes and then I wrote down the result. I did the same with blue and red light and also a test with normal bulb light. Here is the results: _______Green lamp__Blue lamp__Red lamp Bubles:_192________100________109 Temp:__20,9________21,2_______21,2 How can it comes that the Elodea densa produced more oxygen bubbles in green light than in blue and red. I am astonished. Does it have something to do that green light stimulates the flower or is this just an accidental/"short time boost" effect? Or is it like this just on this plant? I would really like to know, because it trigged my thoughts. Have you encountered the same? I would appreciate some advices/help/directions to this matter. Thanks in advance! /Andy P.S. I have attached my Lab results.
Interesting observation Andy. I wrote an article about this subject several years ago as a result of such a request but to be honest haven't read it myself since then. You might take a look as will I and then we can give this another go. http://www.exoticrainforest.com/Will green light kill.html
Andy is it really oxygen that is being produces or bubbles of something else say carbon dioxide. respiration happens in plants when there is no light (and also when there is light... its light independant!) so maybe you were having carbon dioxide forming rather than Oxygen. it would be good to capture the gas forming and test that to see what is being produced you can use a hydrocarbonate indicator to show that http://www-saps.plantsci.cam.ac.uk/articles/fotosyn/photosyn.htm
Hi Andy, Interesting results!! Three questions: 1. Did you do the experiment under the different light regimes with the same plant just changing the filter, or use different plants. If you used the same plant, did you change the water + bicarbonate between tests? 2. In your experiment distance versus bubble production - did you use white light ie without any colour filter? If so, it looks like bubble production was similar in red blue, and white light but much higher in the green light. 3. Did you repeat (= "replicate") the experiment to see if the results were consistent. A possibility to consider (but your white light results are important here), is that perhaps the green filter is allowing more light/energy through (a higher proportion) than your red and blue filters. Brian
Hi Brian, Thanks for advices, really grate troubleshooting. I thought, maybe I have done something wrong... So I repeated the green test, and luckily I got a "better" result. The new was 74 bubbles and a temperature of 20,2 degree Celsius. It depends on which tone of the green colour its used. Now I realised that my first green filter was too transparent why the light looked almost as the sun light (much white). The result must have been something similar to the 3rd thing you mentioned. It was hard to try again, because at first the new green colour was so dark that I couldn't see the bubbles nor the plant. At last I managed. But it's really interesting that the "transparent" green colour I first used, caused the flower to produce a boost of oxygen (I really think the bubbles from the stalk always is oxygen). It caused the flower to produce 65 % more bubbles... As you said, it must have been something with the energy amount. Or the carbon transpiration, even though I have no idea about how it works. Any other ideas? Regards, /Andy
Andy, I am glad to hear that you got the chance to repeat the experiment and that the result helped you to understand what was going on. It is always a good idea to repeat experiments a few times just in case you get, by chance, an odd result (professional biologists will always do this if possible). It is really difficult to make sure that you get the same amount of photosynthetically useful energy from different coloured filters for this type of experiment. Good luck and thank you for sharing your results, Brian
