|Author||Maury, W. J.|
|Source||United States Department of Energy Office of Scientific and Technical Information|
|Subject Keyword||RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT. ♦ CHLOROPLASTS ♦ MEMBRANE TRANSPORT ♦ MAGNESIUM ♦ BIOLOGICAL EFFECTS ♦ ACIDIFICATION ♦ ANTIBIOTICS ♦ ATP-ASE ♦ CATIONS ♦ ENZYME ACTIVITY ♦ INHIBITION ♦ ION EXCHANGE ♦ PHOTOSYNTHESIS ♦ POTASSIUM ♦ SPINACH ♦ ACID ANHYDRASES ♦ ALKALI METALS ♦ ALKALINE EARTH METALS ♦ ANTI-INFECTIVE AGENTS ♦ CELL CONSTITUENTS ♦ CHARGED PARTICLES ♦ CHEMICAL REACTIONS ♦ DRUGS ♦ ELEMENTS ♦ ENZYMES ♦ FOOD ♦ HYDROLASES ♦ IONS ♦ METALS ♦ PHOSPHOHYDROLASES ♦ PHOTOCHEMICAL REACTIONS ♦ SYNTHESIS ♦ VEGETABLES ♦ Chemicals Metabolism & Toxicology- Plants- (-1987)|
|Abstract||Addition of exogenous Mg/sup 2 +/ (millimolar) to illuminated intact spinach (Spinacia oleracea L.) chloroplasts caused acidification of the stroma and a 20% decrease in stromal K/sup +/. Addition of K/sup +/ (10-50 millimolar) reversed both stromal acidification and K/sup +/ efflux from the chloroplast caused by Mg/sup 2 +/. These data suggested that Mg/sup 2 +/ induced reversible H/sup +//K/sup +/ fluxes across the chloroplast envelope. Ca/sup 2 +/ and Mn/sup 2 +/ (2 millimolar) were as effective as 4 millimolar Mg/sup 2 +/ in causing K/sup +/ efflux from chloroplasts and inhibition of O/sub 2/ evolution. In contrast, 10 millimolar Ba/sup 2 +/ indicated that the effects of divalent cations such as Mg/sup 2 +/ cannot be attributed to generalized electrostatic interactions of the cation with the chloroplast envelope. With the chloroplasts used in this study, stromal acidification caused by 2 millimolar Mg/sup 2 +/ was small (0.07 to 0.15 pH units), but sufficient to account for the inhibition of O/sub 2/ evolution (43%) induced by Mg/sup 2 +/. Oligomycin was the only ATPase inhibitor which specifically inhibited photosynthesis in the presence of Mg/sup 2 +/ + K/sup +/, but had little or no effect in the absence of these cations. In the presence of oligomycin much higher concentrations (50 millimolar) of exogenous K/sup +/ were required to reverse Mg/sup 2 +/-induced acidification and inhibition of O/sub 2/ evolution than in its absence. Oligomycin (in the absence of divalent cations) increased the inhibition of photosynthesis caused by sodium acetate. In addition, the chloroplast envelope ATPase was inhibited 45% by oligomycin. These results suggested that H/sup +/ fluxes across the chloroplast envelope are regulated by two mechanisms: an active, oligomycin-sensitive H/sup +/ efflux and a reversible, Mg/sup 2 +/-dependent, oligomycin-insensitive H/sup +//K/sup +/ exchange.|
|Learning Resource Type||Article|
|Publisher Place||United States|
National Digital Library of India (NDLI) is a virtual repository of learning resources which is not just a repository with search/browse facilities but provides a host of services for the learner community. It is sponsored and mentored by Ministry of Education, Government of India, through its National Mission on Education through Information and Communication Technology (NMEICT). Filtered and federated searching is employed to facilitate focused searching so that learners can find the right resource with least effort and in minimum time. NDLI provides user group-specific services such as Examination Preparatory for School and College students and job aspirants. Services for Researchers and general learners are also provided. NDLI is designed to hold content of any language and provides interface support for 10 most widely used Indian languages. It is built to provide support for all academic levels including researchers and life-long learners, all disciplines, all popular forms of access devices and differently-abled learners. It is designed to enable people to learn and prepare from best practices from all over the world and to facilitate researchers to perform inter-linked exploration from multiple sources. It is developed, operated and maintained from Indian Institute of Technology Kharagpur.
NDLI is a conglomeration of freely available or institutionally contributed or donated or publisher managed contents. Almost all these contents are hosted and accessed from respective sources. The responsibility for authenticity, relevance, completeness, accuracy, reliability and suitability of these contents rests with the respective organization and NDLI has no responsibility or liability for these. Every effort is made to keep the NDLI portal up and running smoothly unless there are some unavoidable technical issues.
Ministry of Education, through its National Mission on Education through Information and Communication Technology (NMEICT), has sponsored and funded the National Digital Library of India (NDLI) project.
For any issue or feedback, please write to email@example.com