In the beginning of the experiment the prediction

  • Monash University
  • BIO 1011
  • Lab Report
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between photosystem II and photosystem I. In the beginning of the experiment, the prediction that no reduction will occur in the DCPIP dye was made. Therefore, the small rate in reduction of DCPIP dye observed by the absorbances may have also been a cause of experimental errors. Justification of the slight decrease in absorbance could also be due to the possibility that inhibition between photosystem II and photosystem I did not occur completely. Disturbances in the electron transport chain photosystems II and I observed through boiled chloroplasts and DCMU treatments show very similar results with almost identical absorbance readings over the 60-minute period. In the light reactions, a larger decrease in absorbances was seen throughout the 15-minute intervals as precisely predicted. More specifically, the reaction mix exposed to normal light demonstrated by the purple curve (Figure 1) decreased the most in absorbance. Therefore, this treatment appears to have reduced the DCPIP dye at the fastest rate. Similarly, the reaction mix exposed to red light demonstrated by the red curve (Figure 1) also decreased. In comparison to the reaction mix which
was put under green light demonstrated by the green curve (Figure 1), there was a greater decrease in the absorbances of the red-light treatment. This means the rate at which DCPIP was reduced was greater and therefore photosynthesis occurred faster under a red light compared to a green one. Thiscan be explained by the nature of the chloroplasts which have evolved to absorb light in the red and blue regions of the visible light spectrum whilst reflecting green light.(This report has a lot of sections that are well done. You obviously got the main idea of what was going on in this experiment. I hope my comments at the side clarify where improvements could have been made.)References:M. Pribil, D. Leister, 2017. Reference Module in Life Sciences. Encyclopedia of Applied Plant Sciences (Second edition) Photosynthesis.1, 90-95. doi: 10.1016/B978-0-12-394807-6.00156-8

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