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A TEACHING TOOL: DETERMINING RATES OF CELLULAR RESPIRATION AND PHOTOSYNTHESIS FOR PLANT SPECIES ON GEORGIA COLLEGE'S CAMPUS

Abstract

Students often have difficulty visualizing complex processes such as cellular respiration and photosynthesis, and this can significantly impact the students’ understanding of the relationship between the two processes. Therefore, the goal of this project was to develop a teaching tool for undergraduate educators and students that: (i) provides a published data set for students to compare their own photosynthesis and/or cellular respiration data to, (ii) develops an excel calculator that can convert oxygen (O2) and carbon dioxide (CO2) measured in part per million (ppm) to units that are easier to grasp, and (iii) shows that not all plants have the same rate of photosynthesis. Additionally, this project was developed as an effort to increase student motivation by promoting the application of scientific knowledge to the area they live in. Approximately ten grams of leaves were collected from twenty-six plant species across Georgia College’s campus during October and November 2021. Leaves were placed in containers equipped with Vernier O2 and CO2 sensors, and gases were measured in light and dark conditions. A LabQuest2 data logger was used to collect data for 1800 seconds, and rates of cellular respiration and photosynthesis were determined in triplicate for each plant species. During photosynthesis, CO2 levels typically decrease while O2 levels increase. In our study, this was true for all plants except for Lopopetalum chinense, which has dark purple leaves, that produced CO2 during the light incubation (6.13 + 2.13 ppm min-1). The greatest rates of photosynthesis were observed in the Hydrangea macrophylla leaves (-23.62 + 1.85 CO2 ppm min-1). Total carbon dioxide retention was also calculated for all plant species; hydrangeas (337.67 + 30.44 ppm) and Hosta spp. (311.00 + 71.69 ppm) retained significantly more CO2 compared to the majority of the other plants surveyed. Conversely, Quercus robur, Lopopetalum chinense, and Salvia rosmarinus experienced a net loss in CO2 of -256.00 + 12.12 ppm, -291.00 + 241.02 ppm, and -371.33 + 45.21 ppm, respectively. Using our excel CO2 calculator, these values are equal to 0.92 + 0.04 mg, 1.04 + 0.86 mg, and 1.33 + 0.16 mg of CO2, respectively.

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