Low temperature has a negative impact on plant cells and results in the generation of reactive oxygen species (ROS). In order to study the role of ascorbate under chilling stress, the response of an ascorbate-deficient Arabidopsis thaliana mutant vtc2-1 to low temperature (2°C) was investigated. After chilling stress, vtc2-1 mutants exhibited oxidative damage. An increase in the H2O2 generation and the production of thiobarbituric acid reactive substances (TBARS), and a decrease in chlorophyll content, the maximal photochemical efficiency of PSII (Fv/Fm) and oxidizable P700 were also noted. The ratio of ascorbate/dehydroascorbate and reduced glutathione/oxidzed glutathione in the vtc2-1 mutants were reduced, compared with the wild type (WT) plants. The activities of antioxidant enzymes, such as catalase (CAT) and ascorbate peroxidase (APX), and soluble antioxidants were lower in the vtc2-1 mutants than those in WT plants. These results suggested that the ascorbate-deficient mutant vtc2-1 was more sensitive to chilling treatment than WT plants. The low temperature-induced oxidative stress was the major cause of the decrease of PSII and PSI function in the vtc2-1 mutants. Ascorbate plays a critical role of defense without which the rest of the ROS defense network is unable to react effectively., L. Y. Wang ... [et al.]., and Obsahuje bibliografii
The theory of third-order aberrations of the system rotary symmetrical aspheric thin lenses and the relations for calculation of the shape rotary symmetrical aspheric spectacle lenses with zero astigmatism are stated. A comparison the possibility of the aspheric and spherical spectacle lenses is presented. and Je uvedena teorie aberací 3. řádu soustavy tenkých rotačně symetrických asférických čoček. Jsou odvozeny vztahy pro výpočet tvaru rotačně symetrické asférické brýlové čočky s korigovaným astigmatismem a je provedeno srovnání se sférickou brýlovou čočkou.
Samples of bottom ash and fly ash coming from the combustion of lignite with the addition of limestone, from the cocombustion of lignite and wood residue with limestone and from co-combustion of lignite, wood residue, biological sludges from the waste water treatment plant and municipal waste as well with the addition of limestone were examined. Scanning electron microscopy with X-ray microanalyser were used for study of morphology and chemical composition of ash particles. The results were compared with average composition of bottom ashes, fly ashes and input materials found by X-ray fluorescence spectrometry and with phase composition found by X-ray diffraction method. There were proved no significant differences in the character and the structure of individual samples coming from various regimes of combustion., Vladimír Tomášek, Ondřej Šustai, Jana Seidlerová, Zdeněk Klika, Martin Stach, Zdeněk Weiss and Václav Roubíček., and Obsahuje bibliografii