2011 Theses Bachelor's

Thermal sensitivity of the photosynthetic apparatus of Quercus rubra along a rural to urban transect

Macias, Miguel F.

Rapid urbanization has caused serious adverse environmental impacts across the globe, including increased emissions of carbon dioxide from burning of fossil fuels, reduced natural vegetation, and loss in biodiversity. Urbanization also affects plant photosynthesis and growth. It is of great importance to understand the direct and indirect impact of urbanization on plants as plants are the major sink of atmospheric CO2. In the present study, chlorophyll fluorescence was used to examine the effects of urbanization on the thermal tolerance of photosynthesis of Quercus rubra L., red oak, growing along an urban to rural transect in New York State. The study assessed the yield of chlorophyll fluorescence (Fv/Fm) of red oak under rapidly increasing heat stress, and quantified the critical temperature (Tcrit) at which photosystem II (PSII) protein complex efficiency degrades. The Tcrit was greatest at Lamont–Doherty, a suburban area, followed by rural Black Rock Forest, urban Central Park, and remote Ashokan Reservoir. These patterns indicated that thermotolerance was enhanced in the suburban area, whereas it was decreased in the urban area compared to the remote and rural areas. The effect of temperature alone on maximal PSII efficiency of light capture (Fv/Fm) was less evident, suggesting that the Fv/Fm might be influenced by an interaction of multiple factors, such as temperature, light, CO2 concentration, and nutrient availability. In addition, applying a single regression analysis on combined measurement data from different months, where different environmental factors could be operating, may limit the accurate estimation of Fv/Fm. Although further experimental investigations are needed in order to understand the impact of urbanization on Fv/Fm, the present study contributes toward a better understanding of the effect of urbanization on photosynthesis.