Trifolium repens L. recruits root-associated Microbacterium species to adapt to heavy metal stress in an abandoned Pb-Zn mining area.

Root-associated microbiota provide great fitness to hosts under environmental stress. However, the underlying microecological mechanisms controlling the interaction between heavy metal-stressed plants and the microbiota are poorly understood. In this study, we screened and isolated representative amplicon sequence variants (strain M4) from rhizosphere soil samples of Trifolium repens L. growing in areas with high concentrations of heavy metals. To investigate the microecological mechanisms by which T. repens adapts to heavy metal stress in abandoned mining areas, we conducted potting experiments, bacterial growth promotion experiments, biofilm formation experiments, and chemotaxis experiments. The results showed that high concentrations of heavy metals significantly altered the rhizosphere bacterial community structure of T. repens and significantly enriched Microbacterium sp. Strain M4 was demonstrated to significantly increased the biomass and root length of T. repens under heavy metal stress. Additionally, L-proline and stigmasterol could promote bacterial growth and biofilm formation and induce chemotaxis for strain M4, suggesting that they are key rhizosphere secretions of T. repens for Microbacterium sp. recruitment. Our results suggested that T. repens adapted the heavy metal stress by reshaping rhizosphere secretions to modify the rhizosphere microbiota.

Starmerella jinningensis sp. nov., a yeast species isolated from flowers of Erianthus rufipilus.

Five yeast strains (Ym24403, Ym24404, Ym24408, Ym24409 and Ym24410(T)) were isolated from different flowers of Erianthus rufipilus (Gramineae), a wild plant growing in the phosphorus-rich region in Yunnan Province, south-western China, and were found to be phenotypically and genetically divergent from currently recognized yeast species. Sequence analysis of the D1/D2 domain of the large subunit rRNA gene revealed that the five strains represented a novel species described as Starmerella jinningensis sp. nov. The type strain is Ym24410(T) (= CBS 11864(T) =CCTCC AY 2011002(T)). Phylogenetic analysis based on the D1/D2 region of the large subunit rRNA gene suggested that S. jinningensis sp. nov. is placed within the Starmerella clade.

Drivers and mechanisms of spontaneous plant community succession in abandoned PbZn mining areas in Yunnan, China.

The drivers and mechanisms underlying succession and the spontaneous formation of plant communities in mining wasteland remain largely unknown. This study investigated the use of nature-based restoration to facilitate the recovery of viable plant communities in mining wasteland. It was found that scientific analyses of spontaneously formed plant communities in abandoned mining areas can provide insights for nature-based restoration. A chronosequence ("space for time") approach was used to establish sites representing three successional periods with six successional stages, and 90 quadrats were constructed to investigate changes in plant species and functional diversity during succession in abandoned PbZn mining areas. A total of 140 soil samples were collected to identify changes in soil properties, including plant nutrient and heavy metal concentrations. Then, this paper used structural equation models to analyze the mechanisms that drive succession. It was found that the functional diversity of plant communities fluctuated substantially during succession. Species had similar functional traits in early and mid-succession, but traits tended to diverge during late succession. Soil bulk density and soil organic matter gradually increased during succession. Total nitrogen (N), pH, and soil Zn concentrations first increased and then decreased during succession. Concentrations of Mn and Cd gradually decreased during succession. During early succession, soil organic matter was the key factor driving plant colonization and succession. During mid-succession, soil Zn functioned as an environmental filter factor limiting the rates of succession in mining wasteland communities. During late succession, soil bulk density and competition for nutrient resources contributed to more balanced differentiation among plant species. This thesis proposed that a nature-based strategy for the stabilization of abandoned mining lands could facilitate effective plant community restoration that promotes ecosystem services and functioning.

How do plant morphological characteristics, species composition and richness regulate eco-hydrological function?

Although considerable research has focused on the relationship between ecosystem structure and function, interactions of plant morphological characteristics, species composition and richness with eco-hydrological functions remain unclear. We measured water adherence (i.e. the capacity of a plant species to retain water), documented plant surface morphology and observed surface runoff at three sites in China. The adhering water ratios for each plant species differed, ranging from 17.1% to 151.5% in leaves, and from 14.4% to 41.1% in branches. Small, light-weight, soft, non-cuticularized leaves that were densely situated on small branches showed good water adherence. The next best adherence was found by branches with intermediately coarse surfaces. The plant species with high standing biomass also showed good water adherence, and the contribution of a species to total adherence was dependent upon its aboveground standing biomass. Vegetation parameters strongly affected water adherence, whereas the effect of species richness was not significant. Conversely, species richness showed a significant influence on surface runoff. The effect of plant morphological characteristics and composition constitutes a basic process in the regulation of eco-hydrological function, and vegetation parameters play somewhat different roles in that regulation. The key roles must therefore be considered from a management perspective.

[Study on ultrasonic nebulizer sample feeding system for ICP-AES].

The sample feeding system of inductively coupled plasma atomic emission spectrometry (ICP-AES) is pneumatic nebulization system, but its efficiency is not good. The ultrasonic nebulization technology possesses advantages of high nebulization efficient and fine droplets, and it is free of blocking phenomenon. It has good application perspective in nebulization technology. In the present paper the authors study the working conditions of ultrasonic nebulizer such as carrier gas flow, injection time, injection rate and mode of washing that are likely to affect the detection results, and study the detecting conditions of several elements such as As and Se etc. that have poorly detection limits in normal ICP-AES methods. At the same time, the application of them in biochemical samples was studied. Testing results show that carrier gas flow, injection rate and injection time can greatly affect the intensity of spectral lines, and the ultrasonic nebulizer sample feeding system can increase the spectral line intensity and decrease the detection limit elements such as As, Pb, Se, Bi, Ge, Mo, Cd and Cu by about 10-25 times. Moreover, this ultrasonic nebulizer sample feeding system can reduce the time of memory effect by washing the sample cell.

[Spatial and Temporal Variations in Fertilizer Use Across Prefecture-level Cities in China from 2000 to 2015].

Chemical fertilizer plays an important role in increasing grain production in agricultural systems but overuse also brings a series of environmental problems, such as eutrophication of surface water, deterioration of soil structure, and the decline of agricultural carrying capacity. At present, research on chemical fertilizer use mainly focuses on utilization efficiency while studies on the spatial characteristics of its use are limited. It is also of great significance for the sustainable development of agriculture in China to fully understand the spatial changes in the use of chemical fertilizers. Based on data of pure chemical fertilizer use, sown area, and grain yield in prefecture-level cities from 2000 to 2015, spatial autocorrelation analysis, cold and hot spot analysis, nuclear density analysis, and standard deviation ellipse analysis were applied. The temporal and spatial variations in total fertilizer use and fertilizer load per unit area in 2000, 2005, 2010, and 2015 were compared. The results showed that:① The use of chemical fertilizer in China increased linearly from 2000 to 2015 but it has been in a relatively high agglomeration state in the region. The pure use of chemical fertilizer experienced a process of increasing regional aggregation from 2000 to 2005, weakening from 2005 to 2010, and increasing from 2010 to 2015. ② From a spatial perspective, the total amount of chemical fertilizer applied between 2000 and 2015 showed an increasing trend, shown by an increase in the number of prefecture-level cities and regions in which the use of chemical fertilizer exceeded the standard. The eastern regions of China, which have experienced rapid economic development, such as Guangdong Province and Fujian Province, are over the critical load of chemical fertilizer more and denser than other prefecture-level cities because the proportional reduction in sown area is greater than the increase in chemical fertilizer use. ③ The movement track of the grain production center in China from 2000 to 2015 was not consistent with the movement track of chemical fertilizer usage. Specifically, the center of grain production moves to the northeast, while the center of chemical fertilizer use moves to the west. This demonstrates that the status of commercial grain production in Northeast China is becoming more and more important, and that the use of chemical fertilizer in the western regions of China is gradually increasing. Here, there is a trend for exceeding the standard, which required further attention.

Effects of water exchange rate on morphological and physiological characteristics of two submerged macrophytes from Erhai Lake.

Growth patterns of aquatic macrophytes have been shown to vary in response to hydrological properties; however, such properties are typically characterized by water level fluctuation, flow velocity, flooding season, and sedimentation, but not by water exchange rate (WER). Herein, we experimentally investigated how WER (three levels: exchange 0%, 20%, and 40% of total water per day) affects water and sediment properties, and the consequences that these variations have on the individual responses of two submerged macrophytes, Hydrilla verticillata and Myriophyllum aquaticum which were planted in two different sediment types (sand and clay). In the experiment without ramets, it was found that turbidity, pH value, and dissolved carbon dioxide concentration of the system water were statistically unaffected by WER, while water dissolved oxygen (DO) concentration and sediment oxidation-reduction potential (ORP, in both sediments) consistently increased with increasing WER, regardless of experimental time. In the experiment containing ramets, biomass accumulation and relative growth rate (RGR) of both species gradually increased with increasing WER regardless of sediment type. The mechanisms were related to (a) increased oxygen availability, as indicated by gradually increased water DO concentration and sediment ORP; and (b) enhanced phosphorus (P) and nitrogen (N) absorbing abilities associated with stimulated root growth, reflected in increased mean root length, specific root length, and the root/above-ground biomass ratio, with increasing WER. Additionally, in the experiments containing ramets, significant linear relationships were consistently detected between sediment ORP and root parameters, root parameters and plant nutrients (N and P), and plant nutrients and plant growth conditions (biomass accumulation and RGR). These results demonstrate that WER plays an important role in determining oxygen availability and thus impacts the growth of submerged macrophytes by altering the ability of roots to absorb nutrients, indicating that ecosystem functions are more sensitive to WER than previously recognized.

Toxicity assessment for chlorpyrifos-contaminated soil with three different earthworm test methods.

Earthworm toxicity tests are useful tools for terrestrial risk assessment but require a hierarchy of test designs that differ in effect levels (behavior, sublethal, lethal). In this study, the toxicity of chlorpyrifos contaminated soil on earthworms was assessed. In addition to the acute and chronic tests, an avoidance response test was applied. Earthworms were exposed to sublethal and lethal concentration of chlorpyrifos, and evaluated for acute toxicity, growth, fecundity and avoidance response after a certain exposure period. The test methods covered all important ecological relevant endpoints (acute, chronic, behavioral). Concentration of 78.91 mg/kg, chlorpyrifos caused significant toxic effects in all test methods, but at lower test concentrations, only significant chronic toxic effects could be observed. In present study, chlorpyrifos had adverse effect on growth and fecundity in earthworm exposed to 5 mg/kg chlorpyrifos after eight weeks. The avoidance response test, however, showed significant repellent effects at concentration of 40 mg/kg chlorpyrifos. For chlorpyrifos, concentration affecting avoidance response was far greater than growth and fecundity, it seemed likely that earthworms were not able to escape from pesticide-contaminated soil into the clean soil in field and hence were exposed continuously to elevated concentrations of pesticides.

[Study on solid phase extraction spectrophotometric determination of zinc with 2-(2-quinolylazo)-5-dimthylaminophenol].

A highly sensitive, selective and rapid method for the determination of zinc based on the rapid reaction of zinc(II) with 2-(2-quinolylazo)-5-dimthylaminophenol (QADMAP) and the solid phase extraction of zinc ion with anion exchange resin cartridge was developed. In the presence of pH 8.5 buffer solution and Triton X-100 medium, QADMAP can react with zinc(II) to form a stable 2 :1 complex (QADMAP:Zn(II)). The molar absorptivity is 1.22 x 10(5)L x moL(-1) x cm(-1) at 590 nm. Beer's law is obeyed in the range of 0-1.0 microg x mL(-1). The zinc ions in the samples can be enriched and separated by solid phase extraction with anion exchange resincartridge. Testing results show that recovery for zinc(II) was from 95% to 104%, and RSD was below 3%. This method was applied to the determination of zinc in water and food with good results.

[Epidemiological investigation on congenital heart disease in several regions of Yunnan province].

OBJECTIVE: To investigate the distribution of congenital heart disease (CHD) aged 3 - 18 in several regions of Yunnan province. METHODS: Cross-rectional studies were carried out among 48 638 children from Xishuangbanna, Dali, Baoshan Longling, Luxi Mangshi and Gejiu in Yunnan province with stratified, clustered sampling. RESULTS: The overall morbidity of CHD was 5.08 per thousand with 5.09 per thousand in males and 5.07 per thousand in females. Morbidity rates in different regions were 2.75 per thousand in Xishuangbanna, 7.85 per thousand in Dali, 9.59 per thousand in Baoshan Long ling, 4.80 per thousand in Gejiu, 16.99 per thousand in Luxi Wuchalu. However, in the same area, rates were different among different residents:3.25 per thousand in Gejiu, and was 9.10 per thousand in Laochang stannum mine, 11.20 per thousand in Datunxuanchang; 5.74 per thousand at the city of Baoshan Longling, 11.35 per thousand at countryside; 4.90 per thousand at the city of Dali, 8.71 per thousand at countryside; 1.69 per thousand at the city of Xishuangbanna, 4.40 per thousand at country. Morbidity rates in different ethnic groups were as follows: 5.39 per thousand in Dai, 6.83 per thousand in Jinuo, 0 per thousand in Hani, 8.12 per thousand in Bai, 14.18 per thousand in Jingpo. CONCLUSION: There were significant regional and ethnic differences seen in Yunnan on the mobidity of CHD which was different from the domestic literature reported.