Effects of ultraviolet-B (UV-B) irradiation on ultrastructure, total cellular protein, and PS2 proteins D1 and D2 of Synechococcus sp. PCC 7942 cells was studied. The scanning electron micrographs showed UV-B radiation induced bending of the cells. The transmission electron micrographs revealed disorganization and shift in thylakoid lamellar structure to one side of the cell. The cellular phycocyanin/chlorophyll ratio decreased with increasing UV-B treatment and due to this the colour of cells turned light-green. No apparent change in total cellular proteins was evident, but the contents of two major proteins of PS2, D1 and D2, showed decline due to UV-B irradiation, although to different extent. and Sanjay Chauhan, Ritu Pandey, Gauri S. Singhal.
A crop legume Vigna unguiculata L. (Walp.) and a wild legume Crotalaria juncea L. were evaluated for their relative responses to the oxidative stress injury induced by various doses of UV-B radiation (UV-B, 280-315 nm; 0, 1.0, 1.4, 4.7, and 6.0 kJ m-2 d-1). A dose-dependent damage in lipid peroxidation was determined as an index of membrane injury caused by UV-B. The impact was significantly higher in V. unguiculata than in C. juncea. The specific activities of superoxide dismutase, ascorbate peroxidase, monodehydroascorbate reductase, and dehydroascorbate reductase increased directly proportional to UV-B doses. However, the activities of these enzymes were significantly higher in V. unguiculata than in C. juncea indicating that V. unguiculata was inflicted with more severe oxidative stress injury under UV-B. In C. juncea the glutathione reductase and ascorbate oxidase activities were 35 and 40 % greater than in V. unguiculata, respectively. Further, the non-enzymatic antioxidants ascorbate and glutathione, and their reduced/oxidizes ratios in C. juncea were much greater than V. unguiculata indicating C. juncea has an inherently greater antioxidative potential than V. unguiculata. Thus C. juncea is better adapted to oxidative stress than V. unguiculata by means of efficient cellular antioxidant mechanisms helping to combat the photooxidative stress injury elicited by UV-B.
The present study attempts to determine how some physiological and reproductive functions of olive tree (Olea europaea L., cv. Koroneiki) respond to enhanced UV-B radiation or heat. Enhanced UV-B radiation was applied to (1) three-year-old potted plants in an open nursery (corresponded to ca. 16% ozone depletion), and (2) in vitro cultured pollen samples (220 μmol m-2 s-1, PAR = 400-700 nm + UV-B at 7.5, 15.0, or 22.5 kJ m-2 d-1). Potted olive plants were also subjected to high temperature (38 +- 4°C) for 28 h to mimic heat levels regularly measured in olive growing areas. A significant effect of UV-B on photosynthetic rate was observed. However, enhanced UV-B radiation did affect neither chlorophyll nor carotenoid content, supporting previous reports on hardiness of the photosynthetic apparatus in olive. Increased superoxide dismutase activity was observed in UV-B-treated olive plants (+ 225%), whereas no effect was found in the plants under heat stress. Neither UV-B and nor heat did affect H2O2 accumulation in the plant tissues. However, the same treatments resulted in enhanced lipid peroxidation (+ 18% for UV-B and + 15% for heat), which is likely linked to other reactive oxygen species. The increased guaiacol peroxidase activity observed in both treatments (+ 32% for UV-B and + 49% for heat) is related to the defense against oxidative membrane damage. The observed reduction in pollen germination (20-39%) and tube length (11-44%) could have serious implications on olive yields, especially for low fruit-setting cultivars or in years and environments with additional unfavorable conditions. UV-B and heat effects described here support the hypothesis that plant response to a given stressor is affected by the overall context and that a holistic approach is necessary to determine plant strategies for climate change adaptation., G. C. Koubouris, N. Kavroulakis, I. T. Metzidakis, M. D. Vasilakakis, A. Sofo., and Obsahuje bibliografii
Current scientific theories strive to find one theory, which would describe the origin of life on Earth, but so far none were successful. To succeed i this field, one has to broader their view and accompany the scientific question with philosophy and set firmly the framework of research and define its borders. In order to assess the philosophical part of the work, one needs not to resort to new ideas only, because men and women in the past have already expressed their thoughts. They are however nowadays remembered only in history of arts and philosophy. In our recent article published in Nature Astronomy, we presented a very complex model for the creation of methane and its reprocessing to more complex organic molecules including nucleic acid bases from simple gaseous precursors. The purpose of this work is to show the reoeating cycle of the creation of complex molecules from CO2 and their subsequent destruction back to their basic parent molecules in comparison with the idea of Hieronymus Bosch. and Svatopluk Civiš.
Various types of artificial ant nests (formicaries) are described. These include simple laboratory types to more complex formicaries whose esthetic design is suitable for flat interiors. Formicaries facilitate not only the observation of natural ant behaviour inside a nest, but also of the remarkable practices used by young queens to appropriate the nest of a host ant species. In such equipment it is even possible to arrange a predatory raid by slave-making ants and observe their behaviour inside the attacked nest. Such observations would not have been possible in natural conditions. and Pavel Amcha.