Excessive iron deposition in root apoplast is involved in growth arrest of roots in response to low pH.

The rhizotoxicity of protons (H+) in acidic soils is a fundamental constraint that results in serious yield losses. However, the mechanisms underlying H+-mediated inhibition of root growth are poorly understood. In this study, we revealed that H+-induced root growth inhibition in Arabidopsis depends considerably on excessive iron deposition in the root apoplast. Reducing such aberrant iron deposition by decreasing the iron supply or disrupting the ferroxidases LOW PHOSPHATE ROOT 1 (LPR) and LPR2 attenuates the inhibitory effect of H+ on primary root growth efficiently. Further analysis showed that excessive iron deposition triggers a burst of highly reactive oxygen species, consequently impairing normal root development. Our study uncovered a valuable strategy for improving the ability of plants to tolerate H+ toxicity by manipulating iron availability.

[Effects of Combined Application of Fungal Residue and Chemical Fertilizer on Soil Microbial Community Composition and Diversity in Paddy Soil].

Fungal residue is a unique abundant organic material undervalued in agricultural production. The application of chemical fertilizer combined with fungal residue can not only improve soil quality but also regulate the microbial community. However, it is unclear whether the response of soil bacteria and fungi to the combined application of fungal residue and chemical fertilizer is consistent. Therefore, a long-term positioning experiment in a rice field was conducted with a total of nine treatments. Chemical fertilizer (C) and fungal residue (F) were applied at 0, 50%, and 100% to evaluate 1 the change in soil fertility properties and microbial community structure and 2 the main driving factors of soil microbial diversity and species composition. The results showed that soil total nitrogen (TN) was highest after treatment C0F100 (55.56% higher than in the control), and the carbon to nitrogen ratio (C/N), total phosphorus (TP), dissolved organic carbon (DOC), and available phosphorus (AP) contents were highest after treatment with C100F100(26.18%, 26.46%, 17.13%, and 279.54% higher than in the control, respectively). The amounts of soil organic carbon (SOC), available nitrogen (AN), available potassium (AK), and pH were highest after treatment with C50F100 (85.57%, 41.61%, 29.33%, and 4.62% higher than in the control, respectively). Following the application of fungal residue with chemical fertilizer, there were significant changes in the α-diversity of bacteria and fungi in each treatment. Compared with that of the control (C0F0), different long-term applications of fungal residue with chemical fertilizer did not significantly change soil bacterial ß-diversity but resulted in significant differences in fungal ß-diversity, and the relative abundance of soil fungal Ascomycota and Sordariomycetes significantly decreased after the application of C50F100. The random forest prediction model indicated that AP and C/N were the main driving factors of bacterial and fungal α-diversity, respectively, and AN, pH, SOC, and DOC were the main driving factors of bacterial ß-diversity, whereas AP and DOC were the main driving factors of fungal ß-diversity. Correlation analysis suggested that the relative abundance of soil fungal Ascomycota and Sordariomycetes had a significantly negative correlation with SOC, TN, TP, AN, AP, AK, and C/N. PERMANOVA showed that variation in soil fertility properties, dominant species of soil bacteria at the phylum and class level, and dominant species of soil fungi at the phylum and class level were all best explained by fungal residue (46.35%, 18.47%, and 41.57%, respectively), and variation in bacterial diversity was best explained by fungal residue (23.84%) and to a lesser extent by the interaction between fungal residue and chemical fertilizer (9.90%). In contrast, the variation in fungal diversity was best explained by the interaction between fungal residue and chemical fertilizer (35.00%) and to a lesser extent by fungal residue (10.42%). In conclusion, the application of fungal residue has more advantages than chemical fertilizer in influencing soil fertility properties and microbial community structure changes.

[Novel Insight into the Adsorption Mechanism of Fe-Mn Oxide-Microbe Combined Biochar for Cd(â ¡) and As(â ¢)].

A Fe-Mn oxide-microbe combined biochar (FM-DB) was prepared to simultaneously remove Cd(Ⅱ) and As(Ⅲ) contamination in an aqueous system. In the FM-DB, the best ratio of Fe-Mn oxide (FMBO) and carya cathayensis shell biochar (CCSB) was 3%+3%. The material had good acid resistance, mechanical strength, and mass transfer performance, and the maximum removal rates for Cd(Ⅱ) and As(Ⅲ) in the binary system were 77.29% and 99.94%, respectively. Characterization confirmed that the FM-DB was successfully prepared and had a rich functional group structure. The single-factor adsorption test results for Cd(Ⅱ) and As(Ⅲ) showed that the composite material had a certain adsorption capacity affected by initial pH, equilibration time, and initial concentration for Cd(Ⅱ) and As(Ⅲ) under different conditions. The adsorption isotherm and kinetic data indicated the adsorption equilibrium time for Cd(Ⅱ) and As(Ⅲ) was 3.5 h and 8 h, and the maximum capacity was 59.27 mg·g-1and 84.73 mg·g-1, respectively. The adsorption of Cd(Ⅱ) and As(Ⅲ) was mainly affected by the electron exchange, electron sharing, and complexation on the surface of the material. The whole adsorption process was a combination of single-layer adsorption and multi-layer adsorption on an uneven surface. The adsorption process was a multi-step process, including outer surface diffusion and inner particle diffusion. In addition, comparing the removal rate of composite materials in the single-component system and the binary system, a mutual promotion of adsorption between Cd(Ⅱ) and As(Ⅲ) was found under the binary system. In conclusion, oxide-microbe combined biochar could be an efficient adsorption material and was suitable for the remediation of aqueous system pollution caused by Cd(Ⅱ) and As(Ⅲ).

NRT1.1 Dual-Affinity Nitrate Transport/Signalling and its Roles in Plant Abiotic Stress Resistance.

NRT1.1 is the first nitrate transport protein cloned in plants and has both high- and low-affinity functions. It imports and senses nitrate, which is modulated by the phosphorylation on Thr101 (T101). Structural studies have revealed that the phosphorylation of T101 either induces dimer decoupling or increases structural flexibility within the membrane, thereby switching the NRT1.1 protein from a low- to high-affinity state. Further studies on the adaptive regulation of NRT1.1 in fluctuating nitrate conditions have shown that, at low nitrate concentrations, nitrate binding only at the high-affinity monomer initiates NRT1.1 dimer decoupling and priming of the T101 site for phosphorylation activated by CIPK23, which functions as a high-affinity nitrate transceptor. However, nitrate binding in both monomers retains the unmodified NRT1.1, maintaining the low-affinity mode. This NRT1.1-mediated nitrate signalling and transport may provide a key to improving the efficiency of plant nitrogen use. However, recent studies have revealed that NRT1.1 is extensively involved in plant tolerance of several adverse environmental conditions. In this context, we summarise the recent progress in the molecular mechanisms of NRT1.1 dual-affinity nitrate transport/signalling and focus on its expected and unexpected roles in plant abiotic stress resistance and their regulation processes.

[Simultaneous Immobilization of Arsenic, Lead, and Cadmium in Paddy Soils Using Two Iron-based Materials].

Two iron-based materials, Fe-Ca composite (FeCa) and Fe-Mn binary oxide (FMBO), were applied to immobilize As, Pb, and Cd in heavy metal contaminated paddy soils. Seven kinds of paddy soil (tidal soil) contaminated by arsenic, lead and cadmium were collected from Shangyu, Shaoxing (SY), Foshan, Guangdong (FS), Shaoguan, Guangdong (SG), LiuYang, Hunan (LY), Ganzhou, Jiangxi (GZ), Dushan, Guizhou (DS), and Ma'anshan, Anhui (MAS). The effects of iron-based materials on the dynamic changes of As, Pb, and Cd concentration in soil solution, the stabilization efficacy of available As, Pb, and Cd in soil, and the effects of soil types and properties on stabilization efficacy were studied through soil incubation experiment. The results showed that the content of soil dissolved As, Pb, and Cd were lower in iron-based material treatments than in control throughout the incubation. The addition of two iron-based materials significantly reduced the availability of Cd, Pb, and As. Moreover, the stabilization efficiency of FeCa for As was higher than FMBO, but no significant difference was found in the stabilization efficiency of Pb and Cd between two materials. The stabilization efficiency of As, Pb, and Cd in FeCa treatments could be ordered as GZ > SG > DS and MAS; FS>SY, LY, and SG>MAS; SY, GZ, and DS>MAS, respectively. While the stabilization efficiency for As, Pb, and Cd in FMBO could be ordered as SY, LY, and GZ > DS > FS; FS > GZ > SY; DS > LY > MAS, respectively. In addition, the statistical results showed that the stabilization efficiencies of various soils under the treatment of iron-based materials were significantly correlated with sand content (negatively correlated for As), soil pH (positively correlated for Pb), and clay content (negatively correlated for Cd). In conclusion, the two iron-based materials evaluated in this study may be effective stabilization agents for remediating different types of arsenic-, lead-, and cadmium-contaminated soils.

O Blood Type Is Associated with Unfavorable Distant-metastasis-free Survival in Female Patients with Nasopharyngeal Carcinoma: A Retrospective Study of 2439 Patients from Epidemic Area.

Purpose: To identify the association between ABO blood type and the survivals in nasopharyngeal carcinoma patients. Patients and methods: We retrospectively analyzed 2439 consecutive non-metastasis nasopharyngeal carcinoma patients between January 2001 and December 2004 at the Sun Yat-sen University Cancer Center. Survival outcomes were compared using Kaplan-Meier method. Univariate and multivariate analysis was performed by Cox regression model. Chi-square test was performed to compare categorical variables. Results: In the whole patients, compared with non-O blood type (A, B, and AB) patients, O blood type patients had significantly lower 5-year distant metastasis-free survival (DMFS) (adjusted hazard ratio (aHR)= 1.268, 95% CI 1.010-1.592, P=0.041). Moreover, we observed in female patients, O blood type patients had significantly lower 5-year overall survival (OS), disease-specific survival (DSS) and DMFS than those with non-O blood type (aHR=1.495, 95% CI 1.032-2.165, P=0.034 for OS; aHR=1.566, 95% CI 1.054-2.328, P=0.026 for DSS; aHR=1.779, 95% CI 1.056-2.998, P=0.030 for DMFS). In male patients, there was no significant difference observed between O blood type patients and non-O blood type patients in any survival endpoints. Conclusion: O blood type was associated with an unfavorable DMFS in female patients with nasopharyngeal carcinoma in epidemic area, which might contribute to unfavorable OS and DSS in female patients, even contribute to a lower DMFS in the whole patients. It might be beneficial to predict metastasis so as to guide the treatment in female patients with nasopharyngeal carcinoma in epidemic area.

[Spatial Variation of Heavy Metals in Soils and Its Ecological Risk Evaluation in a Typical Carya cathayensis Production Area].

In recent years, the problem of soil pollution has become more and more serious. The problem of soil heavy metal pollution and its related human health risks has become a hot spot at home and abroad. Carya cathayensis is a unique high-grade woody nut and oil tree from China, and there are few reports on heavy metal pollution in Carya cathayensis plantation soils. Therefore, in order to study the spatial variability of heavy metals and the risk of pollution in Carya cathayensis soil and to promote the sustainable development of the Carya cathayensis industry, Lin'an, a typical Carya cathayensis plantation area, was selected for this study. A total of 188 soil samples were collected from the study area. We systematically studied the spatial heterogeneity of soil heavy metal content in the study area based on GIS technology, geostatistics, Moran's I, and other spatial analysis methods. The single factor pollution index method, the Nemerow comprehensive pollution index method, and the potential ecological risk assessment method were used to evaluate the heavy metal pollution in the study area. The results indicated that the mean content of soil cadmium (Cd), copper (Cu), zinc (Zn), lead (Pb), nickel (Ni), and chromium (Cr) were 0.37, 40.76, 87.61, 30.10, 28.33, 56.57 mg·kg-1, respectively. The average values of Cd and Cu were 1.33 and 2.87 times of the background values, respectively, and the average content of other heavy metals did not exceed the background values. The results of the single factor Nemerow pollution index and potential ecological risk assessment methods showed that heavy metals in the study area exceeded the soil background values in some samples, and the second grade standard of soil environmental quality was exceed for Cd, Cu, Zn, Pb, and Ni in 31.38%, 31.38%, 2.65%, 0.53%, and 17.02% of the samples, respectively. This indicated that the soils in the study area had different accumulation characteristics for Cd, Cu, Zn, Pb, Ni, and Cr, and the local soil had reached pollution levels for Cd, Cu, Zn, Pb, and Ni. Among them, Cd was the most serious, reaching the degree of strong ecological damage, followed by Cu. In general, the heavy metal contents indicated a moderate degree of ecological damage. Based on the analysis of the semi-variance function, the Cd, Cu, and Ni in the soil were best fit with exponential models, the Zn and Pb were better fit with the Gaussian model, and Cr was consistent with the spherical model. Cd, Cu, Pb, Ni, and Cr had the strong spatial autocorrelation, with Nugget/Sill ratios of 12.1%, 4.6%, 14.9%, 2.6%, and 11.2%, respectively, while the Nugget/Sill ratio of Zn was 48.8%, indicating a medium spatial autocorrelation. Moran's I and Kriging interpolation results found that the heavy metals Cd, Cu, Zn, Pb, Ni, and Cr all had obvious spatial distribution patterns and local spatial aggregation phenomena. The high values of heavy metals in soils were mainly found in Taiyang, Daoshi, Qingliangfeng, Heqiao, and Tuankou, and the probability of the risk for contamination by Cd and Cu was higher in the study area. The high values of Cd, Cu, Zn, Ni, and Cr were mainly related to mining, while Pb was closely related to the application of potassium.

[Spatial Variation of Soil Heavy Metals in an E-waste Dismantling Area and Their Distribution Characteristics].

A total of 90 soil samples were collected from the study area. The spatial variation of soil heavy metals and their spatial distribution characteristics were studied. The results indicated that the mean soil concentrations of five heavy metals including Cd, Cu, Zn, Pb and Ni were 0.38, 35.13, 121.38, 35.40 and 28.13 mg·kg-1, respectively. Compared with the background values in Zhejiang, the heavy metals were enriched in paddy soils of the study area. Part of study area was seriously contaminated by heavy metals. For the soil Cd, it had obvious contamination characteristics with a high Pi Avevalue (>1). The Cd, and Pb concentrations in paddy soil had strong coefficients of variance (C.V.): 121.05% and 109.38%, respectively. Soil pH and organic matter (SOM) had significant correlations with most of the total heavy metals and their available fractions in soils. The total heavy metals and their available fractions also had strong correlations, such as total Cd and available Cd in soils. Geostatistics and the Local Moran's Ⅰ were used to identify the contaminated hotspots of these five metals. It was found out that the high soil Cd, Cu, Zn, Pb were located in Daxi and Zeguo towns, which could be attributed to E-waste dismantling and other anthropogenic activities. Soil Ni was mainly influenced by the parent material. The heavy metals in soils may pose a potential threat to local ecosystem and human health.

Lead accumulation and tolerance of Moso bamboo (Phyllostachys pubescens) seedlings: applications of phytoremediation.

A hydroponics experiment was aimed at identifying the lead (Pb) tolerance and phytoremediation potential of Moso bamboo (Phyllostachys pubescens) seedlings grown under different Pb treatments. Experimental results indicated that at the highest Pb concentration (400 µmol/L), the growth of bamboo seedlings was inhibited and Pb concentrations in leaves, stems, and roots reached the maximum of 148.8, 482.2, and 4282.8 mg/kg, respectively. Scanning electron microscopy revealed that the excessive Pb caused decreased stomatal opening, formation of abundant inclusions in roots, and just a few inclusions in stems. The ultrastructural analysis using transmission electron microscopy revealed that the addition of excessive Pb caused abnormally shaped chloroplasts, disappearance of endoplasmic reticulum, shrinkage of nucleus and nucleolus, and loss of thylakoid membranes. Although ultrastructural analysis revealed some internal damage, even the plants exposed to 400 µmol/L Pb survived and no visual Pb toxicity symptoms such as necrosis and chlorosis were observed in these plants. Even at the highest Pb treatment, no significant difference was observed for the dry weight of stem compared with controls. It is suggested that use of Moso bamboo as an experimental material provides a new perspective for remediation of heavy metal contaminated soil owing to its high metal tolerance and greater biomass.

[Effects of Different Kinds of Organic Materials on Soil Heavy Metal Phytoremediation Efficiency by Sedum alfredii Hance].

In this study, a pot experiment was conducted to investigate the effect of clean organic materials i. e., biogas residue (BR), mushroom residue (MR), and bamboo shell (BS) on phytoextraction remediation of two heavy metal contaminated soils (collected from Wenzhou and Fuyang, which referred to "Wenzhou soil" and "Fuyang soil", respectively.) using a cadmium (Cd) and zinc (Zn) hyperaccumulator Sedum alfredii Hance. The results indicated that the effects of organic materials on availabilities of soil heavy metals were different due to different kinds of heavy metals, organic materials, and the application rates of the organic materials. Addition with 5% BR showed the greatest activation to copper (Cu), Zn in Wenzhou soil, and in Fuyang soil 1% BS had the highest activation for Cu, Zn, lead ( Ph) and Cd. Growth of shoot biomass of Sedum alfredii Hance increased with the addition rate of organic materials, and the plant dry weights were increased by 23.7%-93.0%. In Wenzhou soil, only 1% BS treatment had the best effect on Cd uptake and accumulation in shoots of Sedum alfredii Hance, increased by 22.6%, while other treatments were inferior to the control. For Zn, MR treatments were inferior to the control, while other treafments were superior to the control, of which 5% BR, 1% BS and 5% BS exceeded the control by 39. 6%, 32.6% and 23.8%, respectively. In Fuyang soil, for Cd, the treatment effects of 5% BS, 1% BR and 5% BR were the greatest, of which Cd accumulation in shoots exceeded the control by 12.9%, 12.8% and 6.2%, respectively, while Cd accumulations in shoots in all other treatments were less than that of control. For Zn, the treatments of adding organic materials promoted Zn accumulation in shoots of Sedum alfredii Hance, and the best treatments were as follows: 5% BS. 5% BR and 5% MR, exceeded the control by 38.4%, 25.7% and 22.4%, respectively.

[Evolvement of soil bacterial community in intensively managed Phyllostachys praecox stand and related affecting factors].

By using PCR-DGGE and redundancy analysis (RDA), this paper studied the variations of soil bacterial community structure during the intensive management of Phyllostachys praecox stand, and analyzed the soil factors affecting the diversity of the bacterial community. The results showed that after the transformation of paddy field into P. praecox stand, the Shannon and richness indices of soil bacterial community increased significantly. Long-term intensive management of P. praecox stand altered the community structure of soil bacteria, reflecting in the changes of main bacterial populations and the great decrease after an initial increase of the diversity indices of soil bacterial community. Soil pH, soil total nitrogen, and soil available nitrogen and potassium could explain 76.1% of the total variation of soil bacterial community, and soil pH showed the greatest effect though it was not significant, indicating that the evolvement of soil bacterial community under the long-term intensive management of P. praecox stand was the result of the synergistic effects of several soil factors.