68 research outputs found
Significance of radical oxygen production in sorus development and zoospore germination in Saccharina japonica (Phaeophyceae)
We investigated production of radical oxygen species (ROS) in sorus development of sporophyte discs and during zoospore germination of Saccharina japonica (Phaeophyceae) using the fluorescent dye 2',7'-dichlorofluorescein diacetate (DCFH-DA). Quantitative analysis of ROS showed high intracellular production during the stages of zoosporangium formation when paraphyses elongated. In this stage, remarkable ROS release was observed. ROS production was also observed histologically (under a fluorescence microscope) in the elongating paraphyses and the sorus zoosporangia of the sorus. The sorus had significantly higher phenol content, anti-oxidant capacity and ROS scavenging enzyme activities (ascorbate peroxidase, catalase, glutathione reductase and superoxide dismutase) than adjacent non-sorus blade sectors. Thus, intracellular ROS scavenging mechanisms are active during ROS production in sorus formation. In contrast, iodine content was lower in the sorus than in the adjacent non-sorus tissues, suggesting the existence of an anti-oxidant defense mechanism based on iodine efflux. We demonstrated that ROS production is an important phenomenon in the reproduction of the sporophyte in S. japonica. Furthermore, ROS were also observed in the zoospore germination processes. We discuss the physiological and ecological roles of ROS production in sorus formation and zoospore germination
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Solid-state 13C NMR characterization of insoluble organic matter from Antarctic CM2 chondrites: Evaluation of the meteoritic alteration level
Chemical structures of the insoluble organic matter (IOM) from the Antarctic CM2 chondrites (Yamato [Y-] 791198, 793321; Belgica [B-] 7904; Asuka [A-] 881280, 881334) and the Murchison meteorite were analyzed by solid-state 13C nuclear magnetic resonance (NMR) spectroscopy. Different types of carbons were characterized, such as aliphatic carbon (Ali-C), aliphatic carbon linked to hetero atom (Hetero-Ali-C), aromatic carbon (Aro-C), carboxyls (COOR), and carbonyls (C=O). The spectra of the IOM from Murchison and Y-791198 showed two major peaks: Ali-C and Aro-C, while the spectra from the other meteorites showed only one major peak of Aro-C. Carbon distribution was determined both by manual integration and deconvolution. For most IOM, the Aro-C was the most abundant (49.8-67.8%) of all carbon types. When the ratios of Ali-C to Aro-C (Ali/Aro) were plotted with the atomic hydrogen to carbon ratio (H/C), a correlation was observed. If we use the H/C as a parameter for the thermal alteration event on the meteorite parent body, this result shows a different extent of thermal alteration. In addition, IOM with a lower Ali/Aro showed a lower ratio of Ali-C to COOR plus C=O (Ali / (COOR + C=O)). This result suggests that the ratio of CO moieties to aliphatic carbon in IOM might reflect chemical oxidation that was involved in hydrothermal alteration.The Meteoritics & Planetary Science archives are made available by the Meteoritical Society and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform February 202
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