Xiaojun Niu

Physiological and biochemical responses of rice seeds to phosphine exposure during germination

Rice seeds (Tianyou, 3618) were used to examine the physiological and biochemical responses to phosphine exposure during germination. A control (0 mg m(-3)) and four concentrations of phosphine (1.4 mg m(-3), 4.2 mg m(-3), 7.0 mg m(-3) and 13.9 mg m(-3)) were used to treat the rice seeds. Each treatment was applied for 90 min once per day for five days. The germination rate (GR); germination potential (GP); germination index (GI); antioxidant enzymes, including superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT); and lipid peroxidation measured through via malondialdehyde (MDA) were determined as indicators of the physiological and biochemical responses of the rice seeds to phosphine exposure. These indicators were determined once per day for five days. The results indicated that the GR, GP and GI of the rice seeds markedly decreased after phosphine exposure. The changes in the activities of the antioxidant enzymes due to the phosphine exposure were also significant. The exposure lowered the CAT and SOD activities and increased POD activity in the treated rice seeds compared with controls. The MDA content exhibited a slow increase trend with the increase of phosphine concentration. These results suggest that phosphine has inhibitory effects on seed germination. In addition, phosphine exposure caused oxidative stress in the seeds. The antioxidant enzymes could play a pivotal role against oxidative injury. Overall, the effect of phosphine on rice seeds is different from what has been reported previously for insects and mammals.

Facile synthesis of Bi2MoO6–MIL-100(Fe) metal–organic framework composites with enhanced photocatalytic performance

A novel Bi2MoO6–MIL-100(Fe) heterostructure photocatalyst was synthesized by a facile solvothermal method for the first time, and characterized by X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, UV-vis diffuse reflectance spectra, transmission electron microscopy, and photoluminescence spectra. The as-prepared Bi2MoO6–MIL-100(Fe) composites exhibited excellent photocatalytic activity and stability towards the degradation of Rhodamine B (RhB) under visible light irradiation. The introduction of MIL-100(Fe) into semiconductor Bi2MoO6 improved the photocatalytic performance remarkably, and the optimal composite with 9% MIL-100(Fe) content showed the highest photocatalytic activity. According to the active radical trapping experiments, the h+ and ˙O2− radicals were the two main active species in the photocatalytic reaction. The enhanced photocatalytic performance is mainly attributed to the formation of the Bi2MoO6–MIL-100(Fe) heterostructure, which is beneficial to the transfer and separation of photo-generated electron–hole pairs. The possible mechanism of the enhanced photocatalytic performance of the Bi2MoO6–MIL-100(Fe) composites was discussed.

Phosphine in paddy fields and the effects of environmental factors

Ambient levels of phosphine (PH3) in the air, phosphine emission fluxes from paddy fields and rice plants, and the distribution of matrix-bound phosphine (MBP) in paddy soils were investigated throughout the growing stages of rice. The relationships between MBP and environmental factors were analyzed to identify the principal factors determining the distribution of MBP. The phosphine ambient levels ranged from 2.368±0.6060 ng m(-3) to 24.83±6.529 ng m(-3) and averaged 14.25±4.547 ng m(-3). The highest phosphine emission flux was 22.54±3.897 ng (m(2)h)(-1), the lowest flux was 7.64±4.83 ng (m(2)h)(-1), and the average flux was 14.17±4.977 ng (m(2)h)(-1). Rice plants transport a significant portion of the phosphine emitted from the paddy fields. The highest contribution rate of rice plants to the phosphine emission fluxes reached 73.73% and the average contribution was 43.00%. The average MBP content of 111.6 ng kg(-1)fluctuated significantly in different stages of rice growth and initially increased then decreased with increasing depth. The peak MBP content in each growth stage occurred approximately 10 cm under the surface of paddy soils. Pearson correlation analyses and stepwise multiple regression analysis showed that soil temperature (Ts), acid phosphatase (ACP) and total phosphorus (TP) were the principal environmental factors, with correlative rankings of Ts>ACP>TP.

Effects of phosphine on enzyme activities and available phosphorus in rhizospheric and non-rhizospheric soils through rice seedlings

AimsThe objective of this study was to investigate phosphine-induced changes in enzyme activities (acid phosphatase (ACP), urease, invertase, dehydrogenase) and effects of phosphine on available phosphorus in rhizospheric and non-rhizospheric soils.MethodsRice seedlings, as model plant, were exposed to different ambient concentrations of phosphine (0, 1.4, 4.2 and 7.0xa0mgxa0m−3) for a period of 30xa0days, and the enzyme activities and available phosphorus in both rhizospheric and non-rhizospheric soils were monitored for different phosphine concentrations and exposure times.ResultsIn the first 2xa0weeks in the rhizospheric soil, the activities of urease, invertase and dehydrogenase increased slowly with phosphine exposure time in both rhizospheric and non-rhizospheric soils, although ACP activity displayed a slight drop in the rhizosphere; however, the activities of all these enzymes dramatically increased with phosphine concentration and exposure time after 15xa0days. Enzyme activities in rhizosphere soil are generally greater than those in non-rhizosphere soil, exhibiting effects of the rhizosphere. Increase in phosphine exposure concentrations also increased the available phosphorus in rhizosphere and non-rhizosphere soils.ConclusionsPhosphine exposure increases soil enzyme activities and available phosphorus in both rhizosphere and non-rhizosphere which is beneficial for rice growth.

Phosphine-induced physiological and biochemical responses in rice seedlings

Paddy fields have been demonstrated to be one of the major resources of atmospheric phosphine and may have both positive and negative effects on rice plants. To elucidate the physiological and biochemical responses of rice plants to phosphine, rice seedlings (30 d old) were selected as a model plant and were treated with different concentrations of phosphine (0, 1.4, 4.2, and 7.0 mg m(-3)). Antioxidant enzymes, including superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT), and lipid peroxidation measured via malondialdehyde (MDA) were determined as indicators of the physiological and biochemical responses of the rice seedlings to phosphine exposure. Increasing concentrations of phosphine treatment enhanced the activity of SOD, POD, and CAT. In addition, the MDA content increased with increasing concentrations of phosphine. These results suggested that antioxidant enzymes played important roles in protecting rice seedlings from ROS damage. Moreover, rice seedlings were able to cope with the oxidative stress induced by low concentrations of phosphine via an increase in antioxidant enzymatic activities. However, oxidative stress may not fully be prevented when the plants were exposed to higher concentrations of phosphine.

Biogas generation in anaerobic wastewater treatment under tetracycline antibiotic pressure

The effect of tetracycline (TC) antibiotic on biogas generation in anaerobic wastewater treatment was studied. A lab-scale Anaerobic Baffled Reactor (ABR) with three compartments was used. The reactor was operated with synthetic wastewater in the absence of TC and in the presence of 250u2009μg/L TC for 90 days, respectively. The removal rate of TC, volatile fatty acids (VFAs), biogas compositions (hydrogen (H2), methane (CH4), carbon dioxide (CO2)), and total biogas production in each compartment were monitored in the two operational conditions. Results showed that the removal rate of TC was 14.97–67.97% in the reactor. The presence of TC had a large negative effect on CH4 and CO2 generation, but appeared to have a positive effect on H2 production and VFAs accumulation. This response indicated that the methanogenesis process was sensitive to TC presence, but the acidogenesis process was insensitive. This suggested that the presence of TC had less influence on the degradation of organic matter but had a strong influence on biogas generation. Additionally, the decrease of CH4 and CO2 generation and the increase of H2 and VFAs accumulation suggest a promising strategy to help alleviate global warming and improve resource recovery in an environmentally friendly approach.

Matrix-bound phosphine in the paddy soils of South China and its relationship to environmental factors and bacterial composition

PurposePhosphine is a significant gaseous carrier in the P cycle. The matrix-bound phosphine in the paddy soils and its relationship to environmental variables and bacterial community composition were studied.Materials and methodsThe ambient levels of matrix-bound phosphine (MBP) from four distinct sites in South China were investigated. Molecular fingerprint technology polymerase chain reaction–denaturing gradient gel electrophoresis (PCR-DGGE) was used to further explore the potential connections between MBP and composition of bacterial communities.Results and discussionThe relationship between MBP and environmental factors was analyzed to determine the factors affecting the distribution of MBP. Stepwise regression analysis showed that the pH, phosphatase, and organic matter were among the principal environmental factors of the 18 examined factors affecting the MBP levels in paddy soil and explained 38.2xa0% (pu2009<u20090.05) of the total variance observed by principal component analysis (PCA) and redundancy analysis (RDA) analysis.ConclusionsWe found that pH, phosphate, and organic matter had a significant relationship with MBP (pu2009<u20090.05). Sequencing results indicated that MBP might have a close relationship with the bacterial community composition.

Phosphine-induced phosphorus mobilization in the rhizosphere of rice seedlings

PurposeThe aim of this study was to evaluate the role of phosphine in the mobilization of phosphorus in the rhizosphere soil of rice seedlings and to determine the relative efficiency of phosphine in plant P acquisition.Materials and methodsAn indoor simulation experiment was conducted and the matrix-bound phosphine (MBP), phosphorus fractions, and phosphatase activity in the rhizosphere soil samples from rice cultivation, biomass, the plant P, and the root system activity were measured under different phosphine concentrations (0, 1.4, 4.2, and 7.0xa0mgxa0m−3) for a period of 30xa0days.Results and discussionThe results indicated that phosphine treatments enhanced MBP, inorganic P (resin–Pi, NaHCO3–Pi, and NaOH–Pi), and phosphatase activity, as well as the root system activity, and the content of P in the rice seedlings was stimulated with increasing phosphine concentrations. However, organic P (NaHCO3–Po and NaOH–Po) accumulation occurred in the rhizosphere of the rice seedlings. In addition, the content of organic P in the soil samples decreased with increased phosphine concentration.ConclusionsTherefore, relatively high concentrations of phosphine in paddy field could have a positive impact on the effectiveness of phosphorus in rice plants via influencing the rhizosphere properties.

Mechanism of matrix-bound phosphine production in response to atmospheric elevated CO2 in paddy soils

To explore the effect of elevated CO2 concentrations ([CO2]) on phosphine formation in paddy fields, the matrix-bound phosphine (MBP) content, different phosphorus fractions and various carbon forms in soil samples from rice cultivation under varying CO2 concentrations of 400u202fppm, 550u202fppm and 700u202fppm by indoor simulation experiment were determined. This study showed that MBP concentration did not increase significantly with elevated [CO2] over four-week cultivation periods of rice seedlings, regardless of soil layers. MBP had a significant positive correlation with total phosphorus (TP) and inorganic phosphorus (IP), and multiple stepwise linear regression analysis further indicated that MBP preservation in neutral paddy soils with depths of 0-20u202fcm may have been due to conversion from FeP and CaP. Based on redundancy analysis and forward selection analysis, speculated that the formation of MBP in the neutral paddy soils as the response to atmospheric elevated [CO2] was due to two processes: (i) FeP transformation affected by the changes of soil respiration (SCO2) and TOC was the main precursor for the production of MBP; and (ii) CaP transformation resulting from variation in HCO3- was the secondary MBP source. The complex combination of these two processes is simultaneously controlled by SCO2. In a word, the soil environment in the condition of elevated [CO2] was in favor of MBP storage in neutral paddy soils. The results of our study imply that atmospheric CO2 participates in and has a certain impact on the global biogeochemical cycle of phosphorus.

Photocatalytic reduction of Uranium(VI) under visible light with Sn-doped In2S3 microspheres

Visible light-driven conversion of soluble U(VI) to slightly soluble U(IV) has been regarded as a efficient and environmentally friendly technology to deal with uranium containing wastewater. In this paper, we attempted to use photocatalytic technology to reduction U(VI) from aqueous solution by constructing a highly efficient photocatalysts. The novel Sn-doped In2S3 microspheres photocatalyst were synthesized for the first time by a simple hydrothermal method, and characterized with various analytical and spectroscopic techniques to determine their structural, morphological, compositional, optical and photocatalytic properties. In determination of photocatalytic activity, the results showed that all Sn-doped In2S3 samples exhibited greater photocatalytic performance in reduction of U(VI) under visible light than the pure In2S3. The optimum SnIn2S3 photocatalyst with Sn:In molar ratio of 1:4.8 (SnIn2S3) had the highest photocatalytic performance (95% reduction efficiency within 40u202fmin irradiation time), which was approximately 15.60 times faster than that of pure In2S3. The enhanced photocatalytic activity of the optimum SnIn2S3 was largely ascribed to the higher specific surface area, red-shift in the absorption band, the efficient separation of photogenerated electron-hole pairs (e-/h+) and the narrowed band gap with an up shifting of valence band, conduction band potentials. In addition the optimum SnIn2S3 photocatalyst exhibited a good recyclability and stability during the repetitive experiments. Finally, the possible active species and the possible mechanism on basis of the experimental results were discussed in detail.