The Effect Of Light Intensity On The Rate Of Photosynthesis

1919 WordsOct 24, 20178 Pages
The purpose of experimentation was to determine if light intensity had any effect on the rate of photosynthesis as tested through absorbance values, to determine which wavelength of light was most effective for photosynthesis, and to determine which pigments contributed most to each peak of the action spectrum and how the absorption spectrum correlated to the action spectrum. In plant cells, there are two photosystems located in the thylakoid membranes which utilizes light in order to provide power to the electron transport chain. Light energy is absorbed by photosystem I which excites electrons and then moves them to the next stage in the process. It was hypothesized that, as the chloroplasts are exposed to higher light concentrations,…show more content…
The contents of each tube can be found in Table 1-1. The absorbance of each tube was taken at 0 minutes and was accurately measured by a spectrometer. Tube 1 was wrapped in foil, tube 2 was placed 24 cm from a light source, tube 3 was placed 30 cm from a light source, and tube 4 was placed 49 cm from a light source. In front of each light source was a container of water to act as a heat sink in order to prevent heating and denaturing the chloroplast. The absorbance was measured with a spectrometer and recorded at 5-minute intervals for 30 minutes total. The effect of different wavelengths on the rate of photosynthesis was tested using spinach disks and action spectrum light boxes. A cork borer was used to cut approximately 60 disks from spinach leaves. These disks were then placed into a plastic syringe and enough sodium bicarbonate solution was pulled into the syringe to cover the disks. The plunger was slowly depressed in order to push out any air bubbles present in the syringe. The tip of the syringe was covered and then the plunger was pulled for about 10 to 15 seconds at a time in order to create vacuum pressure that would pull the oxygen from the spinach disks. This process was repeated until all the disks sank once the pressure was released due to the lack of oxygen present within them. Five 50mL beakers were filled with 40mL of sodium bicarbonate solution and approximately 10 spinach disks were placed into each of the five beakers. The
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