13 research outputs found
Database of diazotrophs in global ocean: abundance, biomass and nitrogen fixation rates
Marine N2 fixing microorganisms, termed diazotrophs, are a key functional group in marine pelagic ecosystems. The biological fixation of dinitrogen (N2) to bioavailable nitrogen provides an important new source of nitrogen for pelagic marine ecosystems and influences primary productivity and organic matter export to the deep ocean. As one of a series of efforts to collect biomass and rates specific to different phytoplankton functional groups, we have constructed a database on diazotrophic organisms in the global pelagic upper ocean by compiling about 12 000 direct field measurements of cyanobacterial diazotroph abundances (based on microscopic cell counts or qPCR assays targeting the nifH genes) and N2 fixation rates. Biomass conversion factors are estimated based on cell sizes to convert abundance data to diazotrophic biomass. The database is limited spatially, lacking large regions of the ocean especially in the Indian Ocean. The data are approximately log-normal distributed, and large variances exist in most sub-databases with non-zero values differing 5 to 8 orders of magnitude. Reporting the geometric mean and the range of one geometric standard error below and above the geometric mean, the pelagic N2 fixation rate in the global ocean is estimated to be 62 (52–73) Tg N yr?1 and the pelagic diazotrophic biomass in the global ocean is estimated to be 2.1 (1.4–3.1) Tg C from cell counts and to 89 (43–150) Tg C from nifH-based abundances. Reporting the arithmetic mean and one standard error instead, these three global estimates are 140 ± 9.2 Tg N yr?1, 18 ± 1.8 Tg C and 590 ± 70 Tg C, respectively. Uncertainties related to biomass conversion factors can change the estimate of geometric mean pelagic diazotrophic biomass in the global ocean by about ±70%. It was recently established that the most commonly applied method used to measure N2 fixation has underestimated the true rates. As a result, one can expect that future rate measurements will shift the mean N2 fixation rate upward and may result in significantly higher estimates for the global N2 fixation. The evolving database can nevertheless be used to study spatial and temporal distributions and variations of marine N2 fixation, to validate geochemical estimates and to parameterize and validate biogeochemical models, keeping in mind that future rate measurements may rise in the future. The database is stored in PANGAEA (doi:10.1594/PANGAEA.774851)
IPB - IRRI varietal improvement for dryland legume crops for rice based cropping systems : 1985 technical report
Manipulation Through Liquid Culture in the Contents of Sucrose and Glutamine and Their Transformation to Starch and Protein in Wheat Grain
Management Strategy of Obesity in the Public Health System: Proposal of a New Model to Optimize Human Resources and Patient’s Motivation
Development of two powdery mildew and stripe rust resistant wheat lines from ( Triticum turgidum
Interstitial fibrin-fibronectin deposition with T cell infiltrates precedes fibrosis in murine viral myocarditis
This study was carried out to investigate interstitial fibrin and fibronectin deposition and subsequent myocardial connective tissue abnormalities in BALB/c-nu/ + (euthymic and normal T cell function) and BALB/c-nu/nu (athymic and T cell-deficient) mice. Both types of mice were inoculated with encephalomyocarditis virus and sacrificed periodically. Sections of the hearts were stained with haematoxylin-eosin, trichrome, lymphocyte subsets, silver impregnation, and fibrin or fibronectin. In addition, myocardial collagen concentration was measured. Interstitial fibrin and fibronectin appeared in parallel with inflammatory T lymphocytes and myocardial necrosis in the BALB/c-nu/ + mice. The changes increased until 14 days, subsequently decreasing with time. Interstitial fibrosis and abnormal reticulin fibres were absent until 7 days postinfection, and then increased with time until 60 days. In BALB/c-nu/nu mice, in contrast, although myocardial necrosis and fibrin-fibronectin deposition associated with immature T lymphocytes were evident on days 7 and 14, subsequent myocardial fibrosis and reticulin fibre abnormalities were minimal on days 30 and 60. In BALB/c-nu/ + mice, myocardial collagen concentration increased on day 30, but it did not in BALB/c-nu/nu mice. Thus, interstitial fibrin-fibronectin deposition resulting from virus-induced and T lymphocyte-mediated myocyte necrosis precedes the subsequent development of interstitial fibrosis and abnormal reticulin architectures in this model of murine myocarditis