The physicochemical variations of soil, such as temperature, pH, nutrients, and the type of plant cultivation, affect the diversity of cyanobacteria, whether heterocystous or not. The aim of this study was to identify the species of cyanobacteria in a soil and the effect of environmental characteristics on cyanobacteria. Soil samples collected from six different agricultural sites in Al Diwaniyah city/Iraq during September 2016 in the autumn season were analyzed, and the physicochemical characteristics of the samples were measured using approved methods.
The results showed significant correlation and differences between cyanobacteria composition, distribution, and physicochemical factors among soil sites. The Agricultural soil was slightly alkaline and moderately saline and contained abundant nutrients, cations and a high percentage of organic matter. All these characteristics influenced the distribution and diversity of cyanobacteria. Ninety-six species were identified, including four heterocystous species represented by Anabaena, Calothrix, Cylnidrospermum, and Nostoc. However, the non-heterocystous were represented by 13 species: Aphanocapsa, Aphanothece, Arthrospira, Chroococcus, Gloeocapsa, Lyngbya, Merismopedia, Microcystis, Microcoleus, Oscillatoria, Phormidium, Schizothrix, and Spirulina. The dominant species of cyanobacteria was Oscillatoria, followed by Phormidium, Chroococcus, Gleocapsa and Lyngbya. The highest value of Shannon’s and Simpson’s diversities were registered in the Ghammas site, which is a paddy field, but the lowest was registered in the Afak site, cultivated with the alfalfa plant. Soil was classified as finely textured with silty clayey characterization, favorable for cyanobacteria growth. 相似文献
The biological activity of a crude methanolic extract of Trichilia americana (Sesse and Mocino) Pennington (Meliaceae) was assessed using the Asian armyworm, Spodoptera litura (Fabr.) (Lepidoptera: Noctuidae). The extract exhibited strong antifeedant activity in a choice leaf disc bioassay with 0.18 g cm–2 extract deterring feeding by 50%. In nutritional assays, the crude extract reduced growth, consumption and the utilisation of ingested and digested food in a dose-dependent manner when fed to larvae, suggesting both antifeedant and toxic activities. When relative growth rates were plotted against relative consumption rates, the growth efficiency of the S. litura fed on diet containing T. americana crude extract was significantly less than that of control larvae. This result further indicates that the extract acts as both an antifeedant and chronic toxin. Toxicity is only seen following ingestion and was not observed following topical application or injection into the hemocoel. Larvae reared initially on extract-containing diet then transferred to control diet showed nutritional indices comparable to those of larvae fed continuously on control diet. This suggests that the extract is not permanently damaging the insect's digestive tract. The mode-of-action of the extract as a chronic toxin remains unknown. 相似文献
Twenty-seven infants with classical phenylketonuria were evaluated longitudinally for 6 mo while ingesting PhenexTM -1 Amino Acid Modified Medical Food With Iron as their primary protein source. Intake of selected nutrients and biochemical
indices of trace and ultratrace mineral status and plasma retinol and α-tocopherol concentrations were evaluated. The means
of iron status indices (complete blood count, plasma ferritin, iron, transferrin saturation, total iron binding capacity)
and the plasma concentrations of trace and ultratrace minerals (copper, manganese, molybdenum, selenium, zinc) and plasma
retinol and α-tocopherol were in the reference ranges. Vitamin A intakes (r = 0.49,p < 0.05) and plasma retinol-binding protein concentrations (r = 0.42,p < 0.05) were positively correlated with plasma retinol concentrations at 3 mo of study. At 6 mo, concentrations of plasma
transthyretin (r = 0.72,p < 0.01) and retinolbinding protein (r = 0.48,p < 0.05) were positively correlated with plasma retinol concentrations. At 6 mo, concentrations of plasma transthyretin (r = 0.52,p < 0.05) were positively correlated with retinol-binding protein concentrations. Phenex-1 supports normal mean iron status
indices and mean concentrations of trace and ultratrace minerals, retinol, and α-tocopherol when fed in adequate amounts. 相似文献
The eccentric connectivity index, which has recently been employed successfully for the development of numerous mathematical models for the prediction of biological activities of diverse nature, has been reformed to overcome its limitations caused by degeneracy and insensitivity towards heteroatoms. The reformed eccentric connectivity index, termed the eccentric connectivity topochemical index, overcomes the limitations of the eccentric connectivity index by exhibiting very low degeneracy and displaying sensitivity to both the presence and relative position of heteroatoms without compromizing the discriminating power of the eccentric connectivity index. The relationship of the eccentric connectivity topochemical index, eccentric connectivity index and Wieners index with regard to the anti-HIV activity of 2, 3-diaryl-1, 3-thiazolidin-4-one derivatives was subsequently investigated. The values of the eccentric connectivity topochemical index, the eccentric connectivity index and Wieners index of each of 31 analogues comprizing the data set were computed using in-house computer program. Resultant data was analyzed and suitable models developed after identification of active ranges. Subsequently, each derivative was assigned a biological activity using these models, which was then compared with the reported anti-HIV activity. The accuracy of prediction using these models was found to vary from 81 to 90%. The proposed index offers a vast potential for virtual screening of combinatorial libraries, structure property/activity studies and drug design.Figure Basic structure of 2,3-diaryl-1, 3-thiazoidin-4-ones. 相似文献
Known high nitrogen utilization efficiency (NUE1, biomass per unit plant N) China lines of sorghum, China 17 and San Chi San, were compared with relatively low NUE1 U.S. lines, CK60 and Tx623, for both their physiological and biochemical adaptations to tolerate an imposed N stress in the greenhouse. Assimilation efficiency indices (ACi) were significantly greater for the China lines than the U.S. lines at both low and high soil nitrogen levels by about two-fold. Chlorophyll levels in leaves of high NUE1 lines were lower at both soil N treatments. Immunoblots of leaf extracts of sorghum subjected to N stress indicated reduced levels of both phosphoenolpyruvate carboxylase (PEPcase) and ribulose 1,5-bisphosphate carboxylase (Rubisco) while NADP-malic enzyme levels, in general, appear not to be affected. However, NUE1 China line, China 17, retained a significantly greater PEPcase activity than the less-NUE1 U.S. lines, and also the NUE1 China line San Chi San, when grown under N stress conditions. This suggests that PEPcase and enzymes associated with phosphoenolpyruvate synthesis, perhaps, are significant factors in maintaining relatively high photosynthesis under N stress. Carbon isotope ratios of leaves from sorghum genotypes, as indicated by 13C values, became less negative when sorghum plants were grown under N stress, but a genotypic variation either at a low or high N was not observed. 相似文献
The applicability of some diatom methods to quality assessment of differenttypes of Finnish rivers was compared using dominant taxa of diatomcommunities and nutrient level estimations using Trophic Diatom Index(TDI) and a new Phosphorus Diatom Equation (PDE) [Tot. Pcalc (g l-1) = 39 – 0.278 ol-% – 0.117 olme-% – 0.346me-% – 0.006 meeu-% + 1.193 eu-%; n = 97; r2 = 0.742;SE = 17.4]. The overall quality estimations were done by Index ofPollution Sensitivity (IPS) and by Generic Diatom Index (GDI); limit valuesfor quality classes are proposed. 相似文献
The intermediate disturbance hypothesis predicts unimodal relationships between species diversity and disturbance frequency/intensity. To test this hypothesis, species diversity in herbaceous plant communities along a human trampling gradient was investigated by conducting a 4-year experiment in an old-field. In general, species richness (S), the Shannon–Weiner index (H) from plant cover data and species evenness (J) showed negative linear relationships with trampling frequency, in contrast to the prediction of the intermediate disturbance hypothesis. However, the significant relationships between trampling frequency and species diversity were not observed in the fourth year without J, which showed a unimodal relationship. In all experimental years, the number of new species that colonized the plots after 1year was small under frequent trampling, and the number of species lost from the plots was large under infrequent trampling. The relative number and the relative cover of perennial species increased as trampling frequency increased in the first and second years, but this pattern was not observed in the following years because the dominance of perennials further increased at decreasing frequencies of trampling. The similarity in the species composition and the yearly changes in species dominance indicated that trampling at higher frequencies eliminated more trampling-intolerant species only in the early years of the experiment. These results suggest that trampling mediated early changes in species diversity patterns, but competitive interactions were more important in the later experimental years. The time lag in the effects of trampling and competition appears to be attributable to the infrequent occurrence of unimodal patterns of species diversity. 相似文献
Many ecological studies have used diversity indices to assess the impact of environmental disturbance. In particular, ground beetles have been advocated as a good group for assessing disturbance. Most studies on various organisms have used only one or two indices. For our study of the impact of tillage disturbance on carabid beetles in farm fields in southern Ontario, Canada, we used seven different diversity indices (richness, Shannon–Wiener, Berger–Parker, Q-statistic, Margalef, and evenness). Few studies have used deviation from diversity abundance models as a measure of disturbance; however, we use three that are applicable to our data (geometric, log-normal and log-series). The indices and models were used to test the null hypothesis that there is no change in diversity with increasing tillage disturbance, and that there is no difference in diversity with different crops or years. We were not able to reject the null hypothesis that there is any diversity difference among farms. We also found that there was no single diversity index or model that was better than any other at detecting disturbance. These results are supplemented by a meta-analysis of 45 published data sets for the same taxon but in different habitats. The meta-analysis supports the conclusions from our field research that diversity indices and models are not useful for detecting the possible effect of disturbance on assemblages of carabid beetles. 相似文献
Blood analyses for rare-earth element (REE)-high background regions in South Jiangxi show that the population averages of
many of the biochemical indices deviate markedly from normal values in the normal region. These deviations are thought to
be caused by prolonged intake of REE through food chains in view of that the toxicity of other harmful metals such as Pb and
Cd can be neglected because of their insignificant amounts in the environment. In comparison with the normal region, blood
biochemical indices abnormal in the REE-high regions are manifested as low total serum protein (TSP), albumin, β-globulin,
glutamic pyruvic transitanase, serium triglycerides, and immunoglobulin, but high cholesterol. These deviations may be related
to the REE concentration and composition of food chains, and are sex dependent. Certain blood indices (such as TSP) of different
age groups in the LREE-high region indicate that the influence of REE on males is a one-way irreversible process, whereas
females show a strong ability of restoration. 相似文献