Relationship between CO2 Assimilation, Photosynthetic Electron Transport, and Active O2 Metabolism in Leaves of Maize in the Field during Periods of Low Temperature
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Measurements of the quantum efficiencies of photosynthetic electron transport through photosystem II (phiPSII) and CO2 assimilation (phiCO2) were made simultaneously on leaves of maize crops in the United Kingdom during the early growing season, when chilling conditions were experienced, supporting the hypothesis that the relative flux of photosynthesis reducing equivalents to O2 via the Mehler reaction is higher when leaves develop under chilling conditions.Abstract:
Measurements of the quantum efficiencies of photosynthetic electron transport through photosystem II (φPSII) and CO2 assimilation (φCO2) were made simultaneously on leaves of maize (Zea mays) crops in the United Kingdom during the early growing season, when chilling conditions were experienced. The activities of a range of enzymes involved with scavenging active O2 species and the levels of key antioxidants were also measured. When leaves were exposed to low temperatures during development, the ratio of φPSII/φCO2 was elevated, indicating the operation of an alternative sink to CO2 for photosynthetic reducing equivalents. The activities of ascorbate peroxidase, monodehydroascorbate reductase, dehydroascorbate reductase, glutathione reductase, and superoxide dismutase and the levels of ascorbate and α-tocopherol were also elevated during chilling periods. This supports the hypothesis that the relative flux of photosynthetic reducing equivalents to O2 via the Mehler reaction is higher when leaves develop under chilling conditions. Lipoxygenase activity and lipid peroxidation were also increased during low temperatures, suggesting that lipoxygenase-mediated peroxidation of membrane lipids contributes to the oxidative damage occurring in chill-stressed leaves.read more
Citations
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References
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The relationship between the quantum yield of photosynthetic electron transport and quenching of chlorophyll fluorescence
TL;DR: In this article, the quantum yield of non-cyclic electron transport was found to be directly proportional to the product of the photochemical fluorescence quenching (qQ) and the efficiency of excitation capture by open Photosystem II (PS II) reaction centres (Fv/Fm).
Journal ArticleDOI
Assaying for superoxide dismutase activity: Some large consequences of minor changes in conditions
Wayne F. Beyer,Irwin Fridovich +1 more
TL;DR: The effects of experimental variables on assays based upon the use of either ferricytochrome c or nitro blue tetrazolium are investigated to help investigators to avoid the numerous potential pitfalls which necessarily surround these assay methods.
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Selected methods for the determination of ascorbic acid in animal cells, tissues, and fluids
TL;DR: This chapter discusses selected methods for the determination of ascorbic acid in animal cells, tissues, and fluids and suggests that prompt stabilization is especially important in the case of plasma or serum.