Photsynthesis Using Dcpip

Topics: Photosynthesis, Carbon dioxide, Plant Pages: 2 (653 words) Published: October 15, 2008
Thus, because blue light has a higher absorbance by plant photosynthetic pigments and has a higher energy wavelength than red light, we predicted that juniper needles placed in blue light would photosynthesize faster than juniper needles placed in red light. We measured the rate of change in CO2 concentration due to juniper needles. For each sample, we placed the needles into a chamber connected to the CO2 monitor and measured the rate of change of CO2 concentration for 10 minutes under red light and then 10 minutes under blue light. We ran three independent trials and alternated which color of light to which the leaves were first exposed. We weighed the juniper needles in each sample so that we could control for differences in mass; the rates of change of CO2 concentration were calculated per gram of juniper needles. We did not test the rate of respiration of the juniper needles in the absence of light because we assumed that the rate of respiration was constant for each sample of juniper needles. We monitored the rate of change in CO2 concentration of an empty chamber as a control to demonstrate that any change in CO2 concentration was a result of the juniper leaves and not the chamber itself changing the concentration of CO2. The rate of change of CO2 concentration in the empty chamber was nearly 0, so we did not have to correct/adjust any values during the experiment due to this control. Plants in red light produced less CO2 over time (photosynthesized faster) than the plants in the blue light for each of our three trials. Two of the three trials in the red light were negative values, reflecting a decrease in the concentration of CO2. These values of the photosynthesis (plus respiration) rates in red light were 0.443, -0.141, and -1.1 ppm/g/min with a mean value of -0.27 ppm/g/min. The values of photosynthesis (plus respiration) rates in blue light were 2.449, 1.667, and 2.997 ppm/g/min with a mean value of 2.36 ppm/g/min. A t-test comparing the mean...
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