The uptake and translocation of selected elements by cole (Brassica) grown using oasis soils in pot experiments

Pot experiments were conducted on cole (Brassica) grown in soils jointly treated with traces of two heavy metals cadmium (Cd) and zinc (Zn). As the concentration of heavy metals in the soil increased, the uptake of these metals by the plants rose. However, the ratio of heavy metal concentration in soil to uptake by plants increased at a slower rate. Bioavailability of heavy metals considered between the roots and soil using non-linear regressions was shown to be statistically significant. Similarly, the bioavailability of these two heavy metals between leaves and roots using a linear regression was also statistically significant. The bioconcentration factors (BCFs) for Cd and Zn were 0.282 and 4.289, respectively. Significant variation of BCF with the heavy metal bioavailability in soil was noted from non-linear models. The transfer factors (TFs) were 4.49 for Cd and 1.39 for Zn. The Zn concentration in leaves under all treatments did not exceed threshold set standards, but Cd levels exceeded these standards when the concentration of Cd in the soil was more than 1.92 mg kg^?1 dry weight (dw). Data indicate that cole (Brassica) is not a suitable crop for oasis soils because of plant contamination with heavy metals, especially Cd.     

Effects of nutrient concentration and litter cover on quantitative shoot parameters and belowground biomass of Zizania latifolia (L)

This study investigated the effect of nutrient concentration and litter cover on the development of quantitative shoot parameters and belowground biomass (BGB) production of Zizania latifolia. Zizania latifolia is a common emergent aquatic species in East Asia. Four treatments were done at the study site, and were observed between May 2003 and December 2005. The treatments are namely, high nutrient (HN) with litter cover (HNWL), high nutrient without litter cover (HNNL), low nutrient (LN) with litter cover (LNWL), and low nutrient without litter cover (LNNL). The quantitative shoot parameters and BGB had higher values for treatments with high nutrient (HN) compared to the low nutrient treatments (LN), independent of the presence of litter cover. Furthermore, the life span of the secondary shoots was also higher in HN treatments compared to LN treatments. The BGB productivity was higher in the HNNL treatment compared to the other treatments. The LNWL treatment showed the least developed quantitative shoot parameters, e.g. plant height, and the lowest BGB for Z. latifolia. It was generally observed that the combined effects of low nutrients and litter cover negatively affected shoot development and BGB production.     

Urban-rural nitrogen emission from household food consumption in China: spatial pattern and dynamics analysis

The nitrogen emission from household food consumption (NEHFC) has played a vital role in sustainability development. Recent changes in household dietary have significantly accelerated reactive nitrogen emissions in China. However, the spatial patterns and dynamics of these flows between urban and rural areas remain unclear. Based on material flow and spatial-temporal analysis, our study investigated the patterns of Chinese urban-rural NEHFC during 1993–2015. Increasingly apparent regional disparities were found in both the spatial patterns of urban-rural NEHFC during the study period. Notably, the spatial autocorrelation of urban NEHFC demonstrated a ‘U’ type, compared with a recent decreasing Moran’s I index of rural NEHFC. Moreover, the regional spatial-temporal variation of per capita urban NEHFC exhibited ‘South (High)-North (Low)-Middle (Fast)’ trend. By contrast, the hotspot of per capita rural NEHFC mainly concentrated in South-eastern China with a distinct regional changing of ‘Middle-east (Fast) & west (Slow).’ The Social-Economic and Regional-Development Index were far more critical than the Natural-Geographic Index to the spatial-temporal variation of per capita urban NEHFC, whereas the rural NEHFC was driven by the combined actions of all the three indexes. Our study highlighted the necessity of ‘Location-Suitable’ and ‘Urban-rural recycling’ nitrogen management strategies for reducing the risk of NEHFC in China.     

The oligopeptides production by the feather-degrading bacterium Bacillus methylotrophicus H0北大核心CSCD

Due to the high nutritive value of oligopeptides and the waste of feather resources, this study aimed at screening efficient strains of bacteria able to rapidly degrade feathers and produce large quantities of value-added oligopeptides. In order to assess the potential yield of oligopeptides, the promising strain H0 was selected from 16 feather-degrading microorganisms. To identify the strain, we analyzed the morphological and physiological characteristics of different strains, and carried out a gene sequence analysis of their 16S rRNAs. A single factor experiment was used to promote feather degradation and oligopeptide production, and the characteristics of the oligopeptides produced were also analyzed by Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS). The strain was identified as Bacillus methylotrophicus. The optimal initial pH and temperature for oligopeptide production were 11 and 40 °C, respectively. After 72 h of fermentation under these optimal conditions, the feathers were almost completely degraded, with a 38.19% of oligopeptides (accounting for 67.53% of the total soluble peptides) and a 11.11% of free amino acids produced. LC-MS/MS analysis indicated that the oligopeptides were mainly short peptides containing 5-10 amino acids, with a molecular mass (Mr) of less than 1 300. Moreover, the peptides were abundant in branched-chain amino acids, that might be responsible for the antioxidant property of the feather hydrolysate. Our results demonstrate the great capability of B. methylotrophicus H0 in feather degradation and oligopeptide production. This research provides a high-quality microorganism resource, and the scientific basis for the development of feather-derived oligopeptide products. © 2018 Science Press. All rights reserved.     

The physiological response and iron and potassium contents in the hairy roots of Brassica rape L. Under cadmium stress北大核心CSCD

The experiments were conducted to investigate the tolerance and enrichment capabilities by elucidating the physiological response and cadmium impact on iron and potassium accumulation amounts of brassica rape hairy roots under different cadmium concentrations by using liquid suspension culture method. The results showed the following. (1) The growth of hairy roots was not significantly different under low cadmium concentrations (below 100 μmol/L), whereas it was obviously inhibited under high cadmium concentrations (more than 100 μmol/L). Further, the maximum fresh weight of brassica rape hairy roots reached 4.34 g under 25 μmol/L cadmium stress after 7 days. (2) The content of ROS in brassica rape hairy roots increased with increasing concentrations of cadmium; the antioxidant enzyme activities of brassica rape hairy roots (SOD, POD, and CAT) decreased first and then increased with increasing cadmium concentrations under 1-day stress, whereas showed an opposite trend under 7-day stress. (3) PI staining and MDA content indicated that cellular damage was more serious with increasing cadmium concentrations. (4) With the increase of cadmium concentrations, cadmium content of hairy roots increased and reached maximum of 2.97 mg/g under 400 μmol/L cadmium stress after 7 days. The iron content also increased significantly with the maximal weight of 14.52 mg/g after 1-day cadmium stress, whereas no significant difference was noted under 7-day cadmium stress. The potassium content under 7-day cadmium stress was 1.6 times of that after 1-day stress (15.73 mg/g). The study showed that the physiological response of Brassica rape hairy roots was correlated with the concentration and time of cadmium stress. Moreover, cadmium stress caused metabolic disorders of iron and potassium in the hairy roots, but the hairy roots of Brassica rape had better enrichment effect on cadmium. © 2018 Science Press. All rights reserved.     

Flow cytometric analysis of nuclear DNA stained with SYBR Green I in Phaeodactylum tricornutum北大核心CSCD

This study aimed to investigate a suitable method to stain the nuclei of Phaeodactylum tricornutum with a flow cytometer equipped with a 488-nm laser to detect the DNA. Exponentially growing cells were fixed using a 70% ethanol, a 1% glutaraldehyde and a 1% formaldehyde solution, respectively. The samples were treated with RNase A and were then stained with propidium iodide. Samples not treated with RNase A were stained with SYBR-green I. All these samples were observed under a fluorescence microscope and the content of the nuclear DNA was quantitated by flow cytometry. Specific fluoresce spots indicate that fluorescence was detected only in the nuclei of cells stained with SYBR-green I and non-RNase A treated, using fluorescence microscopy. The result of flow cytometry showed that the DNA histogram of cells stained with SYBR-green I had distinct G1 and G2/M peaks, with a fit degree (RCS) of about 3, and a coefficient of variation (CV) of around 8.6%. However, the DNA histograms of cells stained with propidium iodide had a higher CV value, a poor fit degree, and no obvious G1 and G2/M peaks. The results indicate that SYBR Green I is an adequate detection method for nuclear DNA quantitation in cells of P. tricornutum using a flow cytometer equipped with a 488-nm laser, and without RNase A treatment. © 2018 Science Press. All rights reserved.     

In situ push-pull method to determine ground water denitrification in riparian zones

To quantify ground water denitrification in discrete locations of riparian aquifers, we modified and evaluated an in situ method based on conservative tracers and 15N-enriched nitrate. Ground water was "pushed" (i.e., injected) into a mini-piezometer and then "pulled" (i.e., extracted) from the same mini-piezometer after an incubation period. This push-pull method was applied in replicate mini-piezometers at two Rhode Island riparian sites, one fresh water and one brackish water. Conservative tracer pretests were conducted to determine incubation periods, ranging from 5 to 120 h, to optimize recovery of introduced plumes. For nitrate push-pull tests, we used two conservative tracers, sulfur hexafluoride and bromide, to provide insight into plume recovery. The two conservative tracers behaved similarly. The dosing solutions were amended with 15N-enriched nitrate that enabled us to quantify the mass of denitrification gases generated during the incubation period. The in situ push-pull method detected substantial denitrification rates at a site where we had previously observed high denitrification rates. At our brackish site, we found high rates of ground water denitrification in marsh locations and minimal denitrification in soils fringing the marsh. The push-pull method can provide useful insights into spatial and temporal patterns of denitrification in riparian zones. The method is robust and results are not seriously affected by dilution or degassing from ground water to soil air. In conjunction with measurements of ground water flow-paths, this method holds promise for evaluating the influence of site and management factors on the ground water nitrate removal capacity of riparian zones.     

Arsenic accumulation in the hyperaccumulator Chinese brake and its utilization potential for phytoremediation

The unique property of arsenic hyperaccumulation by the newly discovered Chinese brake (Pteris vittata L.) fern is of great significance in the phytoremediation of arsenic-contaminated soils. The objectives of this study were to (i) examine arsenic accumulation characterized by its distribution pattern in Chinese brake, and (ii) assess the phytoextraction potential of the plant. Young ferns with five or six fronds were transferred to an arsenic-contaminated soil containing 98 mg As kg-1 and grown for 20 wk in a greenhouse. At harvest, the Chinese brake produced a total dry biomass of 18 g plant-1. Arsenic concentration in the fronds was 6000 mg kg-1 dry mass after 8 wk of transplanting, and it increased to 7230 mg kg-1 after 20 wk with a bioconcentration factor (ratio of plant arsenic concentration to water-soluble arsenic in soil) of 1450 and a translocation factor (ratio of arsenic concentration in shoot to that in root) of 24. The arsenic concentrations increased as the fronds aged, with the old fronds accumulating as much as 13,800 mg As kg-1. Most (approximately 90%) of the arsenic taken up by the Chinese brake was transported to the fronds, with the lowest arsenic concentrations in roots. About 26% of the initial soil arsenic was removed by the plant after 20 wk of transplanting. Our data suggest that the arsenic hyperaccumulating property of the Chinese brake could be exploited on a large scale to remediate arsenic contaminated soils.