The Effect Of Various Shading Conditions On Absorbance

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The effect of various shading conditions on absorbance was studied using chloroplasts from Spinacia olderacea leaves. DCPIP assays can be used to assess photosynthetic activity because it is an electron acceptor that absorbs light based on the amount of electrons transferred to it during Photosystem II. Shade exposure will decrease the amount of photosynthesis the will occur, which reduces the amount of electrons transferred to DCPIP and therefore there will be less of a change in absorbance. Enriched chloroplasts were placed in conditions in which mesh was placed over light sources that created 25% shading, 50% shading, and 75% shading. Tubes of chloroplasts were also placed in no shading and completely dark conditions to serve as controls. It was hypothesized that if the percentage of shade increases, then the percent change in absorbance will decrease. Absorbance was tested using a Spectrometer at time zero, 10, 20 and 30 after the reaction began and the tubes were placed in their conditions. The hypothesis was supported in this experiment because as compared to the light, all of the shading conditions had caused a significant decrease in change in absorbance, but a plateau was observed in change in absorbance over 50% shaded. Since each shading condition did result in a significant decrease in percent change of absorbance, shading techniques can be used to prevent superfluous vegetation growth because a decrease in percent change showed diminished activity of Photosystem

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