Field tests to study the dynamics of weed inhibition of allelopathic rice and microbial physiological traits of rice rhizospheric soils北大核心CSCD

The weed inhibition of allelopathic rice PI312777 and nonallelopathic rice Lemont, allelopathic potential of rice rhizospheric soils, as well as the microbial physiological traits of rice rhizospheric soils, were studied by field tests after weedremoving and weed treatments. The results showed that the inhibitory rate of PI312777 at the 7-leaf stage on paddy weeds was 85.82%. Results of the Soil-Agar Sandwich method revealed that the allelopathic potential of PI312777 rhizospheric soils on the inhibitory rate of plant dry weight of barnyard grass was significantly higher at the 5-leaf stage than that at the 3-leaf stage, and increased by 20.16% from the 3-leaf stage to the 5-leaf stage after weed treatment. When at the same leaf stage, the soil microbe biomass carbon and soil respiration, the number of soil bacteria, and activity of soil enzymes (urease, protease, and sucrase) were significantly higher in PI312777 rhizospheric soils than in Lemont rhizospheric soils; they were also higher after the weed-removing treatment than after weed treatment. The largest increase of soil allelopathic potentials and soil microbial physiological indexes in PI312777 rhizospheric soils appeared from the 3-leaf stage to the 5-leaf stage. In case of weed treatment, the allelopathic potential of PI312777 rhizospheric soils on the soil microbe biomass carbon, soil respiration, the number of soil bacteria, activity of urease, activity of protease, and activity of sucrase increased by 53.11%, 51.56%, 38.97%, 44.83%, 60.00%, and 41.92%, respectively, from the 3-leaf stage to the 5-leaf stage. These results indicated that rice allelopathy had a close relationship with the activity of rhizospheric soils. Rice allelochemicals lead to the change of soil microbes; rice allelopathy is a process based on plant-soil interaction. © 2018 Science Press. All rights reserved.     

Spatial distribution and controlling factors of heavy metals contents in paddy soil and crop grains of rice–wheat cropping system along highway in East China

There is consensus concerning the heavy metal pollution from traffic emission on roadside agricultural land. However, few efforts have been paid on examining the contamination characteristics of heavy metals in roadside paddy-upland rotation field, and especially in combination with detailed quantitative analysis. In this study, we investigated the concentrations of heavy metals (Pb, Cd, Cr and Zn) in soil and crop grains of the rice-wheat cropping system along a major highway in East China in 2008 and analyzed the spatial distribution characteristics of heavy metals and their influencing factors with GIS and Classification and Regression Trees (CART). Significantly elevated levels of heavy metals in soil, rice and wheat grains indicated the heavy metals contamination of traffic emission in roadside rice-wheat rotation field. The contamination levels of Cd, Cr and Zn in wheat grain were higher than rice grain, while that of Pb showed an opposite trend. Obvious dissimilarities in the spatial distributions of heavy metals contents were found between in the soil, rice and wheat grains, indicating that the heavy metals contents in the roadside crop grains were not only determined by the concentrations of heavy metals in the paddy soil. Results of CART analysis showed that the spatial variation of the heavy metals contents in crop grains was mainly affected by the soil organic matter or soil pH, followed by the distance from highway and wind direction. Our findings have important implications for the environmental assessment and crop planning for food security along the highway.     

Residues of 14C‐γ‐HCH in paddy after dusting,and the fate of γ‐HCH during refining process of rice bran oil

Paddy (rice) plants were dusted with 10% HCH containing ¹⁴C‐Γ‐HCH, at the rate of 2.5 kg a.i./ha and ¹⁴C‐residues were determined in different fractions of rice. Rice bran (0.187 ppm) had more of ¹⁴C‐residues than grain (0.026 ppm) and husk (0.042 ppm). The rice bran oil contained 0.129 ppm HCH residues. While degumming, dewaxing, alkali refining and bleaching had no effect, deodorisation alone eliminated 99.5% of added ¹⁴C‐residues in rice bran the oil during refining process.     

Geochemistry of trace elements in paddy (rice) soils of Sri Lanka – implications for iodine deficiency disorders (IDD)

Iodine Deficiency Disorders (IDD) are a common health problem prevalent in the wet zone of Sri Lanka with a prevalence of >25 of the population. In comparison, in the dry zone of Sri Lanka IDD occurs in <10 of the population. Seventy soil samples from 14 villages selected on the basis of the incidence of goitre, were collected and analysed for 13 trace elements using ICP-MS. In order to identify any prevailing differences in antecedent chemical environments, soil samples from each pre-selected village were classified into three groups in terms of their geographical location. Among the elements investigated, the total soil concentrations of Rb, Sr, Ba, Mn and Co are lower in the wet zone of Kalutara. In contrast, total soil Rb, Sr, Ba and Mn contents are higher in the dry zone of Anuradhapura. Further soil total Mo and Nb levels are relatively similar in all pre-selected study locations. The high endemic goitre regions (IDD >25 of the population) show low levels of Rb, Sr, Ba, and Mn and higher levels of V, Cr, Co, Ni, Cu, Zn and Pb as compared with moderate and non-goitre areas. Factor analysis was used to exploit the correlation structure present in data and yielded three groups in all cases. This indicated that most transition group elements and iodine are associated with the Mn phase in the low IDD areas whereas iodine shows a high affinity for the organic phase in high IDD regions. The variable distribution of trace elements, therefore, must be due to differences in mobility and capacity for incorporation into the structure of secondary minerals or organic phases.     

Assessing the fractionation and bioavailability of heavy metals in soil–rice system and the associated health risk

Environmental Geochemistry and Health - This study developed a method to build relationships between chemical fractionations of heavy metals in soils and their accumulations in rice and estimate...     

Agro-biodiversity in rice–wheat-based agroecosystems of eastern Uttar Pradesh,India: implications for conservation and sustainable management

In this study, we analysed the indigenous practices of agro-biodiversity, changing patterns of cropping systems and conservation of agriculturally important natural resources of rice–wheat-based agroecosystems. The research was carried out in three villages of Azamgarh district, eastern Uttar Pradesh, India. Participatory approaches and personal interviews were combined to collect the data from 180 farmers. The results indicated that resource-poor (RP) farmers, by applying traditional practices of natural resource conservation, outperform their rich (RR) counterparts in conserving agro-biodiversity. Increase in irrigation facilities, adoption of improved crop varieties, commercialisation of farming and socio-economic changes have threatened the agro-biodiversity and related natural resources of these agroecosystems. For most of the crops, the RP farmers had better production stability as compared to the RR ones because the former tend to apply more sustainable and ecologically sound indigenous practices. A negative growth rate was observed in the area/numbers and production of legumes, livestock, pasture lands and community forestry. Women, who are the local custodians of conserving indigenous biodiversity (uncultivated species) and crop varieties through localised knowledge and sociocultural institutions, had significantly higher knowledge on agro-biodiversity than men. We concluded that integration of farmers’ eco-friendly practices with formal science and policy-making in a participatory mode may enhance sustainability of functions of agroecosystem leading to the strengthening of adaptive practices in changing climate and socio-economic scenario.     

Effect of different pearling times on the quality of hull-less barley rice北大核心CSCD

Hull-less barley is a special food crop rich in various nutrients in Qinghai-Tibet Plateau. Six-pearling is often used to produce commercial hull-less barley rice in order to improve its rough taste and inferior cooking quality. This study evaluated the differences in the nutritional, cooking, sensory, and storage qualities of hull-less barley rice with different pearling times to obtain suitable processing conditions for the production of high-quality hull-less barley rice. With increasing pearling time, the contents of vitamin B6, vitamin E, dietary fiber, iron, zinc, phenols, and flavonoids significantly decreased to a large extent, protein and vitamin B3 decreased slightly, the contents of total starch and β-glucan increased significantly, and γ-aminobutyric acid (GABA) initially increased and then decreased. The peak, trough, and final viscosity of whole grain barley were 1 860.50 cP, 914.50 cP, and 2 150.00 cP, respectively, and increased after six-pearling to 4 219.00 cP, 2 628.00 cP, and 5 074.00 cP, respectively. At the same time, the water absorption and volume expansion of the pearled hull-less barley increased significantly. The hardness of pearled hull-less barley reduced from 4 708.50 g to 2 282.00 g, its adhesiveness increased from 0.00 to -7.33, and its taste and sensory quality exhibited better. The activities of α-amylase, polyphenol oxidase, lipase, and catalase in pearled hull-less barley slightly decreased. Hull-less bran flour is rich in a variety of nutritional components and could be a potential resource with great developmental value. In general, hull-less barley rice obtained from three-pearling has high nutritional value, high cooking quality, low enzyme activity, and low energy consumption; therefore, it can be used to produce high-quality barley rice. This study provides important information for high-quality pearled hull-less barley and further utilization of barley bran flour. © 2022 Science Press. All rights reserved.     

Response of the grain yield and quality of hybrid rice to weak light stress北大核心CSCD

In this study, three rice varieties, Byou268 (low light-sensitive type), Nei5you768 (intermediate type), and Yixiangyou1108 (low light-tolerant), were used as experimental materials to investigate the yield and quality responses of different rice varieties to low light stress under normal light (CK) and low light (SH). The results showed the following: (1) Compared with normal light, the decrease in Yixiangyou1108’s 1 000-grain weight, grain number per spike, and seed setting rate under low light treatment were much lower than those of Nei5you768 and Byou268. The yield decline of Yixiangyou1108 (46.5%) was significantly lower than that of Nei5you768 (56.5%) and Byou268 (69.8%). Yixiangyou1108 showed strong tolerance to low light stress in terms of 1 000-grain weight, seed setting rate, grain number per panicle, and yield. (2) Compared with normal light, the reduction in grain length and width of Yixiangyou1108 under low-light treatment was significantly greater than that of Byou268; however, the reduction in the length-width ratio did not reach a significant level. The amylose content and gel consistency of the rice were significantly reduced. The reduction in amylose content of Yixiangyou1108 (24.5%) was significantly lower than that of Nei5you768 (28.1%) and Byou268 (30.6%); however, the decrease in gel consistency of Yixiangyou1108 (14.7%) was significantly higher than that of Nei5you768 (9.8%) and Byou268 (8.1%). After low light treatment, the characteristic values of the RVA curve of rice changed. The peak viscosity and breakdown viscosity of Yixiangyou1108, Nei5you768, and Byou268 were significantly decreased, but the cold glue viscosity and setback viscosity were significantly increased, while there was no significant difference in the peak time and peak temperature. The response of 1 000-grain weight, grain number per spike, and seed setting rate under low light stress can be used as a yield index of rice breeding with low light tolerance; rice grain type, amylose, and gel consistency; and peak viscosity and hot paset viscosity in RVA characteristic values can be used as quality indexes of low-light-tolerant rice material breeding. © 2022 Science Press. All rights reserved.     

Preliminary toxicity evaluation of water from rice fields using cost‐effective microbiotests

A study was performed in a Protected Area (Natural Reserve of Sado Estuary) in 1996, to evaluate the acute toxicity for aquatic life of surface water from rice fields treated with pesticides, particularly with molinate and quinclorac. As a preliminary assessment, the following rapid toxicity tests were used: “Rotoxkit F”;, “Thamnotoxkit F”; and the recently introduced “Daphtoxkit F magna”; and “Algaltoxkit F”;. Water samples were collected from: a water source for irrigating the rice fields, two rice plots, a drainage channel and from Sado river in which the water is discharged. The results showed that samples from the rice plot treated with molinate were more toxic than those obtained from rice plot treated with quinclorac. Water samples from the river were the most toxic, causing 100% of immobility in all organisms and a substantial inhibition in the algal growth. Water collected from the drainage channel in late July, was also found to be quite toxic. The results obtained until now indicate that some characteristics of these microbiotests, like their rapidity, simplicity and relatively low cost, make them a practical tool to evaluate acute effects of pesticides in freshwater ecosystems. They may also contribute to suggest some changes in pesticides use to promote agricultural practices with lower impact to aquatic life.     

Adsorption of Cu（Ⅱ） on rice straw char from acidic aqueous solutions

研究了稻草炭对Cu（Ⅱ）的吸附特征,探讨了Cu（Ⅱ）的吸附机制.结果表明,稻草炭对Cu（Ⅱ）有很高的吸附容量,Langmuir方程能很好地拟合Cu（Ⅱ）吸附等温线,因此可以描述稻草炭对Cu（Ⅱ）的吸附,其预测的Cu（Ⅱ）在pH 4.5和pH 5.0时的最大吸附量分别为0.628 mol.kg-1和0.763 mol.kg-1.稻草炭对Cu（Ⅱ）的吸附量随体系pH升高而增加,但吸附Cu（Ⅱ）的解吸率呈相反的变化趋势.当吸附体系pH≤4.5时,Cu（Ⅱ）解吸率大于55%,说明此时以静电吸附为主;在较高pH条件下Cu（Ⅱ）以非静电吸附机制为主.红外光谱的分析结果表明,稻草炭表面有丰富的—COOH和—OH等含氧官能团,Cu2＋与含氧官能团形成有机络合物导致—COOH吸附峰位移.Cu（Ⅱ）吸附使稻草炭颗粒的Zeta电位向正值方向位移.结果说明Cu（Ⅱ）在稻草炭表面发生了专性吸附.     

Effects of planting density on the microclimate of rice population with different panicle-types and its yield components北大核心CSCD

Split-plot field experiments, with variety as the main plot, were designed to analyze the microclimate and character of R498 (curved panicle) and R499 (erect panicle) varieties of rice during the full heading day and on the 20th day after full heading. The planting densities assigned to the subplots were 0.23 m (line spacing) × 0.12 m (hole spacing), 0.27 m × 0.14 m, 0.33 m × 0.17 m, 0.38 m × 0.20 m, and 0.40 m × 0.21 m. The results showed that for all the planting densities, the maximum temperature of R499 increased by 1.52 ℃ on an average during the full heading stage, but decreased by 0.66 ℃ on the 20th day after full heading, in comparison to those of R498. The mean daily light intensities of R498 and R499 in sparse planting (0.38 m × 0.20 m, 0.40 m × 0.21 m) were higher than those of other planting density treatments during the full heading stage, being 43.56% and 16.22% higher, respectively, than that of the lowest daily light intensity. The daily light intensity of R498 was hindered by close planting (0.23 m × 0.12 m, 0.27 m × 0.14 m) while that of R499 was inhibited by sparse planting on the 20th day after the full heading stage. The rates of decrease of vertical light intensity of R498 and R499 in sparse planting were the highest among all the planting density treatments, their rates of decrease being 97.96% and 92.56%, respectively, during the full heading stage, and 94.81% and 91.10%, respectively, on the 20th day after the full heading stage. When the planting density was decreased, the variability of plant height, tiller number, and panicle curvature were greater for R499 than those of R498. The rates of incidence of sheath blight for R498 and R499 in the planting specification of 0.38 m × 0.20 m were 66.67% and 68.89%, respectively, which was the most serious among all the planting density treatments. On increasing the effective spike number and panicle weight, both R498 and R499 produced the highest yields with the planting specification of 0.27 m × 0.14 m, among all the planting density treatments. Even when the density was excessively reduced, the value of yield components did not increase any further. Thus, it is better to plant rice with curved panicles (R498) in a reasonable planting density (neither too close nor too sparse), and to plant rice with erect panicles in a reasonably close planting density. © 2018 Science Press. All rights reserved.     

Effect of fluoride content in drinking water in Tricity on its concentration in urine of pre‐school children

Fluorides were analysed in drinking water and in urine of pre‐school children from different districts of Tricity (Gdańsk, Gdynia and Sopot). Concentration of fluorides in urine was found to depend on their content in drinking water. The two years (1997–98) study was made for 15 preschool children populations; each numbering in 10–20 individuals. The fluorides were determined by flouroselective electrode potentiometry.     

Role of specific microbial communities in the bioavailability of iron in Doñana National Park

The Doñana National Park contains highly complex microbial communities that play critical roles in the bioavailability and biogeochemical cycling of elements. In this study, we analyzed the formation of Fe-rich films on the surface of shallow waters at Doñana National Park as a model for future applications in bioremediation. Phytoplankton composition and abundance, physicochemical measurements, culture enrichments, and molecular detection of microorganisms were determined during this study. Natural samples were incubated in the laboratory and enrichments producing similar phenomena were obtained. Bacteria belonging to the genera Enterobacter were the major participants in surface Fe-film formation in laboratory enrichments. Film formation was dependent on wind exposure and only those sites protected from the direct influence of wind developed these films. A higher concentration of euglenophytes was found in the proximity of film-covered waters. Available iron (Fe²⁺) and total Fe concentrations were high (18.8 and 46.6 mg/L, respectively) underneath the surface film, and higher than in film-free waters and pore-sediment water. The concentration of phosphate and its availability were higher in the iron-rich film sediment, as 61% of total P was bound to iron oxy-hydroxides. Our results provide evidence of the link between P and Fe biogeochemical cycling in aquatic systems on sandy soils at the Doñana National Park. In addition, they provide significant insights into the bioavailability of these elements with potential interest in the role of microorganisms for metal sequestration in natural environments and utilization in bioremediation processes.     

Importance of freshwater flow in terrestrial–aquatic energetic connectivity in intermittently connected estuaries of tropical Australia

δ¹³C was used to identify seasonal variations in the importance of autochthonous and allochthonous sources of productivity for fish communities in intermittently connected estuarine areas of Australia’s dry tropics. A total of 224 fish from 38 species were collected from six intermittently connected estuarine pools, three in central Queensland (two dominated by C₃ forest and one by C₄ pasture) and three in north Queensland (one dominated by C₃ and two by C₄ vegetation). Samples were collected before and after the wet season. Fish collected in the two forested areas in central Queensland had the lowest δ¹³C, suggesting a greater incorporation of C₃ terrestrial material. A seasonal variation in δ¹³C was also detected for these areas, with mean δ¹³C varying from −20 to −23‰ from the pre- to the post-wet season, indicating a greater incorporation of terrestrial carbon after the wet season. Negative seasonal shifts in fish δ¹³C were also present at the pasture site, suggesting a greater dependence on carbon of riparian vegetation (C₃ Juncus sp.) in the post-wet season. In north Queensland, terrestrial carbon seemed to be incorporated by fish in the two C₄ areas, as δ¹³C of most species shifted towards slightly heavier values in the post-wet season. A two-source, one-isotope mixing model also indicated a greater incorporation of carbon of terrestrial origin in the post-wet season. However, no seasonal differences in δ¹³C were detected for fish from the forested area of north Queensland. Overall, hydrologic connectivity seemed to be a key factor in regulating the ultimate sources of carbon in these areas. It is therefore important to preserve the surrounding habitats and to maintain the hydrologic regimes as close to natural conditions as possible, for the conservation of the ecological functioning of these areas.     

Speciation of heavy metals in suspended particulates in urban air†

An anayltical procedure based on a sequential extraction scheme is applied to samples of suspended particulates from an urban area of Barcelona. This area presents high levels of air pollution owing to automotive emissions and industrial activity.

The procedure allows the partitioning of particulate trace metals into four fractions: soluble and exchangeable, bound to carbonates and iron‐manganese oxides, bound to organic matter and residual. In this work, the chemical associations of Fe, Pb, Cu, Mn, Cr and Cd have been investigated.

In the analysed samples, only the cadmium is predominantly in the first fraction whereas the other metals are largely associated to carbonates and Fe‐Mn oxides.     

Speciation of particulate trace metals in sediments of Anarbe reservoir∗

Total concentration and chemical forms of heavy metals in samples of sediment from a drinking water reservoir have been analysed. The result of total metal contest shows Fe and Mn concentration increase along the reservoir, from 4.4% in Fe and 0.07% in Mn in the end part to 6.4% Fe and 0.22% Mn at the dam. However, a decrease in organic matter along the reservoir is observed. In order to test the accuracy of the digestion methods used, a standard reference material was also analysed.

Trace metal concentrations, with exception of Cadmium, Pb and Mn, found in fraction 5 are higher than those observed in the others extractions, Fe, Ni, Zn, Cr and Cu content in non‐residual fraction is found mainly in moderately reducible fraction, but the percentage of this fraction in each metal is very different.     

Mycelial culture of wild Inonotus hispidus parasitizing the jujube tree and the cultivation conditions of its fruit body on rice medium北大核心CSCD

Inonotus hispidus is a kind of rare medicinal fungus, and its natural resources are very scarce. Currently, the artificial cultivation technology of I. hispidus is not completely developed, and this reflects on its extremely low biological conversion rate and long cultivation period. In order to improve the bioconversion rate and shorten the production cycle of I. hispidus, we first analyzed the mycelia culture conditions of the collected I. hispidus, and then we further explore the method of domesticated cultivation of its fruiting body in rice medium. During the process of mycelial culture, the suitable temperature, pH, carbon source, and nitrogen source for mycelial growth were selected using the mycelial growth rate as index. During the domesticated cultivation of the fruiting body, the suitable culture medium for its growth was selected using the bioconversion rate as index. Screening results of mycelial culture conditions showed that the optimal culture conditions for the growth of mycelium of the wild I. hispidus were: temperature of 25 °C, initial pH of 6.0, glucose as the carbon source, and yeast extract powder as the source of nitrogen. The results of the domesticated cultivation showed that the biotransformation rate of I. hispidus was higher when using rice as the main medium substrate. The optimal cultivation conditions were: a 0.2% yeast extract content in the nutrient solution, a 1:1.6 ratio of rice to nutrient solution, and a 4 mL inoculum of the liquid strain. Under these conditions, it took about 4 days for the mycelium to grow over the cultivation medium. The time required for the differentiation of the primordium to form fruit bodies was about 20 days, and the bioconversion rate reached 28.70% ± 5.05%. The results of this study indicate the feasibility of using rice as the main substrate for the cultivation of I. hispidus, and it also provide new insights for the finding of new cultivation substrates for other rare medicinal fungi. © 2018 Science Press. All rights reserved.     

Contributing institutional factors of rural environmental pollution in the process of modernization in China —In the perspective of the efficiency of environmental management system

With the development of rural pollution, its characteristic and institutional factor should be studied for pollution control through economics and sociology. Based on the data gathered from investigations by several government sectors, rural environmental pollution can be divided into two types by its sources: internal source type and external source type. The internal source type is the main component of rural pollution at present, which can be further divided into three types. Research shows that the contributing institutional factors of rural pollution issues and the effectiveness of environmental management system over rural pollution can be summarized as distinctiveness. In essence, the rural pollution issue results from the dualism of rural and urban areas’ inadaptability to rural modernization. In detail, the contributing factors can be summed up on three institutional levels. There are obvious loopholes in rural environmental management system which, in the meantime, is incapable and inadaptable to rural pollution control. There exist similar questions in the related public service system, which are intensified by inappropriate reform which brought about incompatible incentive in the recent years. However, in the eleventh five-year plan period, there are advantageous trends in the three institutional levels.     

Advances in research of airborne microbes in subway systems北大核心CSCD

Subway systems are indispensable for transportation in modern cities, with the air being easily polluted by microbes owing to the enclosed and crowded environment. The microbiological characteristics of subway aerosols have attracted the attention of researchers worldwide during recent years. This review aimed to evaluate the sampling and analyzing methods suitable for detecting airborne microbes in subway systems. Active air sampling methods and molecular biology techniques based on polymerase chain reaction (PCR) such as 16S rRNA gene sequencing, metagenomics, and quantitative PCR demonstrated great potential in microbial analysis of aerosols because they can provide accurate and comprehensive information. Temporal and spatial distributions of airborne microbes, as well as the factors influencing their distribution characteristics, were also discussed by critically reviewing worldwide literature on subway microbiome studies. The concentration and composition of airborne bacteria and fungi in subway can vary dramatically with time and space. The critical factors determining microbial community structure and composition include temperature, relative humidity, carbon dioxide concentration, number of passengers, presence of platform screen door, ventilation systems, and so on. The review suggests that future studies on standardized sampling and analyzing protocols are required to obtain contamination levels of subway airborne microbes and to establish the relationship between microbial monitoring data and public health risks. © 2018 Science Press. All rights reserved.