UBC Undergraduate Research

Photosynthesis and Transpiration Rate as Indicator of Carbon Sequestration and the Effect of Three Hormones : Jasmonic Acid, Ethylene and Cytokinin on Leaf Senescence of an Evergreen Thuja plicata (Western Red Cedar) Ghiam, Mona


The objective of this study was to measure photosynthesis and transpiration rate of Thuja plicata as indicators of carbon sequestration through environmental and seasonal changes. Photosynthesis and transpiration rates were measured automatically by CI-340 Handheld photosynthesis machine from November 10, 2017 to March 28, 2018. Our hypothesis matched our results that both photosynthesis and transpiration rates decrease during winter compared to fall and spring. Photosynthesis and transpiration rates were highest in the beginning of November and they both dropped by about 20% in winter, reaching lowest in middle of January. Another objective of this study was to observe whether the presence of exogenous hormones ethylene (CEPA), cytokinin (BAP) and jasmonic acid (JA) promotes leaf senescence in the evergreen Thuja plicata. 5mL of 1uM, 10uM, and 100uM concentration stock solutions of each hormone and 0.7-0.8 grams of leaflets were added to a total of 40 petri dishes; samples were taken from each plate once a week for up to 6 weeks. We hypothesized that JA and CEPA promote leaf senescence and BAP prevents leaf senescence. It was observed that JA was the first hormone to cause leaf senescence and CEPA was the second hormone that caused leaf senescence, and in both cases chlorophyll and proteins were degraded as indication of leaf senescence; BAP prevented leaf senescence in the first 3 weeks but at the end of week 6, 100uM BAP induced leaf senescence. Disclaimer: “UBC SEEDS provides students with the opportunity to share the findings of their studies, as well as their opinions, conclusions and recommendations with the UBC community. The reader should bear in mind that this is a student project/report and is not an official document of UBC. Furthermore readers should bear in mind that these reports may not reflect the current status of activities at UBC. We urge you to contact the research persons mentioned in a report or the SEEDS Coordinator about the current status of the subject matter of a project/report.”

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