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Gewählte Master / Diploma Thesis:

Moritz Schneck (2019): New Methods to Estimate Day Respiration and the CO2 Compensation Point of Photosynthesis by Comparing C3 and C2 Plants.
Master / Diploma Thesis - Institut für Botanik (Botany), BOKU-Universität für Bodenkultur, pp 82. UB BOKU obvsg

Data Source: ZID Abstracts
Abstract:
Respiratory and photorespiratory CO2 release drastically lowers the primary production of land plants. Improved estimates for the rate of both processes are vital for predicting crop and ecosystem productivity. Photorespiration results from the breakdown of metabolites produced when O2 instead of CO2 is fixed by Rubisco. Photorespiration is typically estimated using the photorespiratory CO2 compensation point (Γ*), the CO2 concentration at Rubisco where photosynthesis equals photorespiration. The Laisk method, developed in 1977, remains the most commonly used method to determine Γ* and also provides an estimate for day respiration in light (Rd). Hence it has become an important tool to quantify both forms of respiratory losses during photosynthesis. Two new methods based on the widely-used biochemical model of photosynthesis were examined to estimate Γ* and Rd. Leaves from different individuals of Spinacia oleracea and Diplotaxis tenuifolia, grown under standardized conditions, were measured with the Laisk, the new “Constant Ci” and the new “Constant A” method. The two selected species differ where the photorespiratory CO2 is released: in Spinacia oleracea (C3) all photosynthetically active cells release photorespiratory CO2, in Diplotaxis tenuifolia (C2 or C3-C4 intermediate), a large portion of photorespiratory CO2 is only released in the bundle-sheath cells. Literature suggests that using the Laisk method with C2 plants typically results in very low or negative Γ* estimates. The results of this thesis indicate that all three methods produce comparable Γ* estimates for Spinacia oleracea, but Rd estimates are typically lower when estimated with the Laisk method. However, for the C2 plant, only the Laisk method produces very low Γ* estimates. The results of the new methods are more in line with the idea that Γ* is relatively conserved among species. This thesis concludes that the two new developed methods are able to produce reliable estimates for both species.

Beurteilende(r): Hietz Peter
1.Mitwirkender: Tholen Daniel

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