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Photosynthetic Oxygen Evolution

University of Turku (Finland)
Involved scientists: Vesa Havurinne and Esa Tyystjärvi

Photosynthesis produces oxygen and therefore plant scientists often measure the rate of oxygen evolution. The traditional methods of oxygen measurement require extensive maintenance and the methods are prone to electrical interference. We have found the optical oxygen meter FireStingO2 from PyroScience reliable and fast and feel that this is the future of oxygen measurement in photosynthesis research.

In order to measure photosynthetic oxygen evolution in liquid medium, we used a calibration method based on hydrogen peroxide and catalase to ensure the precise reading in oxygen concentrations above the level of air-saturated water. The calibration method is based on the stoichiometric coefficients of the catalase reaction H2O2 à 2H2O + O2. Further comparison between the results obtained using different calibration methods (hydrogen peroxide, single-point and 2-point calibration with oxygen-free water) showed no clear deviation from each other, and therefore it is obvious that even the very simple single-point calibration in water is enough for oxygen evolution experiments.

By 3D-printing we were able to create a perfect fit cuvette system for a type OXB430-OI oxygen minisensor, an external temperature sensor and the FireStingO2 central module (FSO2-1). Temperature control is provided by water circulation and the sample is mixed with a magnetic stirrer (Figs. 1 & 2). Oxygen measurements from isolated thylakoid membranes using dimethylbenzoquinone as electron acceptor (Fig. 3) showed the same results as obtained with an oxygen electrode using the same sample.

For further information, please contact Esa Tyystjärvi (esatyy(at)utu.fi).