Die Wirkung von Photooxidantien auf Sommerweizen (Triticum aestivum L. Star) |
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Authors: | Jürgen Maguhn Helmut Selinger Alexander Ziegler-Jöns Dietmar Knoppik |
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Affiliation: | 1. GSF-Institut für ?kologische Chemie, c/o Lehrstuhl für ?kologische Chemie der TU München-Weihenstephan, D-85350, Freising 2. Lehrstuhl für Physik Weihenstephan, Technische Universit?t München, D-85350, Freising
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Abstract: | The effect of short-time fumigation with the peroxidic photooxidants ozone, peroxyacetyl nitrate (PAN), and hydrogen peroxide (H2O2) on the gas exchange of wheat leaves was investigated. Two types of experiments are to be distinguished: - Fumigation is carried out at atmospheric CO2 partial pressure (350 μbar) and the assimilation and transpiration rates are followed simultaneously.
- The alteration of CO2-response curves by fumigation is determined; from this, characteristic photosynthetic parameters can be calculated.
With this method, statements about the reaction of both photosynthesis as a whole and specific reaction sites within the most important photosynthetic processes are possible. Ozone in concentrations of 260–280 ppb causes a primary perturbation of the photosynthetic apparatus, whereby the carboxylation rate is affected to nearly the same extent as the electron-transport rate.PAN (120 ppb) causes a reduction in the assimilation rate, primarily due to the closing of the stomata. H2O2 affects the gas exchange only in concentrations of above 1 ppm, whereby the reduction of the assimilation rate represents an almost pure stomatal effect. All three fumigants cause an increase in the respiration rate, which may point to an activation of detoxification and repair mechanisms. |
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