New herbicide models from benzoxazinones: aromatic ring functionalization effects

The utility of benzoxazinones and some of their synthetic derivatives in the search for new leads for herbicide model development has been widely discussed. As the benzoxazinone skeleton contains three different potential areas for functionalization (C-2, N-4, and aromatic protons H-5, H-6, H-7, and H-8), and the first two have already been optimized, the main objective of this work was the substitution of aromatic protons for different substituent types and the study of the effects of the prepared chemicals on selected standard target species (STS) and weeds. Thus, different combinations of aromatic substituents, including methoxy, methoxycarbonyl, fluorine, chlorine, and trifluoromethyl, were introduced at different positions. Phytotoxicity results were successfully correlated with steric and electronic molecular parameters, the resulting molecular volume (V) and dipole moment (mu) being the most influential ones. Halogenations at C-6 and fluorination at C-7 were the most successful modifications. Compounds 6-fluoro-(2H)-1,4-benzoxazin-3(4H)-one (6F-D-DIBOA), 7-fluoro-(2H)-1,4-benzoxazin-3(4H)-one (7F-D-DIBOA), and 6-chloro-(2H)-1,4-benzoxazin-3(4H)-one (6Cl-D-DIBOA) had the highest phytotoxic activities. The dose-response profiles on wheat and two of its most common weeds (Lolium rigidum Gaud. and Avena fatua L.) were compared by means of a proposed selectivity index, which displayed 7F-D-DIBOA as the most selective of the tested benzoxazinones.     

Optimization of benzoxazinones as natural herbicide models by lipophilicity enhancement

Benzoxazinones are plant allelochemicals well-known for their phytotoxic activity and for taking part in the defense strategies of Gramineae, Ranunculaceae, and Scrophulariceae plants. These properties, in addition to the recently optimized methodologies for their large-scale isolation and synthesis, have made some derivatives of natural products, 2,4-dihydroxy-(2H)-1,4-benzoxazin-3-(4H)-one (DIBOA) and its 7-methoxy analogue (DIMBOA), successful templates in the search for natural herbicide models. These new chemicals should be part of integrated methodologies for weed control. In ongoing research about the structure-activity relationships of benzoxazinones and the structural requirements for their phytotoxicity enhancement and after characterization of the optimal structural features, a new generation of chemicals with enhanced lipophilicity was developed. They were tested on selected standard target species and weeds in the search for the optimal aqueous solubility-lipophilicity rate for phytotoxicity. This physical parameter is known to be crucial in modern drug and agrochemical design strategies. The new compounds obtained in this way had interesting phytotoxicity profiles, empowering the phytotoxic effect of the starting benzoxazinone template in some cases. Quantitative structure-activity relationships were obtained by bioactivity-molecular parameters correlations. Because optimal lipophilicity values for phytotoxicity vary with the tested plant, these new derivatives constitute a more selective way to take advantage of benzoxazinone phytotoxic capabilities.     

Response of soil microbial communities to the herbicide mesotrione: A dose-effect microcosm approach

Mesotrione is a new selective herbicide used for maize crops. The responses of microbial communities of a chernozem soil (Limagne basin, France) to pure or formulated (Callisto^®) mesotrione, applied at three different doses [one fold field rate (1 × FR), 10 × FR and 100 × FR], were studied using a laboratory microcosm approach. The effects were assessed on the prokaryotic cell abundance, the overall microbial activities (substrate-induced respiration (SIR) and dehydrogenase activity (DHA)) and the genetic structure of the bacterial and fungal communities (temporal temperature/denaturing gradient gel electrophoresis (TT/DGGE)). Mesotrione dissipation was similar whatever the formulation applied and the amounts dissipated were positively correlated to application rates. Several biodegradation products including the metabolites 4-methylsulfonyl-2-nitrobenzoic acid (MNBA) and 2-amino-4-methylsulfonylbenzoic acid (AMBA) were detected from day 42 post-treatment, in 10 × FR and 100 × FR treated soils. No response of the soil microbial communities was detected in soil spread with both the 1 × FR applications. Overall soil microbial activity was stimulated from day 6 by 10 × FR of Callisto^® and more strongly by 100 × FR of pure mesotrione and Callisto^®, whereas prokaryote abundance did not increase before day 95 in both the 100 × FR treatments. Genetic structural shifts recorded from day 42 in the bacterial and fungal communities were small and mainly attributable to variations in band intensity. Maximum dissimilarity of the bacterial and fungal genetic structures between control and 100 × FR treated soils did not exceed 12% and 28%, respectively. The general pattern was that more consistent effects occurred with increasing exposure times, especially in both the 100 × FR treated soils. These microbial responses could be due to the stimulation of (i) adapted mesotrione-degrading microorganisms and (ii) the activity of resistant heterotrophic microbial groups promoted by dead biomass from sensitive organisms. In addition, at 100 × FR doses, pure mesotrione seemed to induce stronger microbial responses than Callisto^®, formulation which contains adjuvants with potential side-effects on some microbial populations. This experimental approach indicated that pure mesotrione and Callisto^® affected soil microbial communities, but the effects were only detected at doses far exceeding the recommended field rates.     

Growth and development of Cirsium arvense in relation to herbicide dose,timing of herbicide application and crop presence

The aim of this study is to assess control effects of 2-methyl-4-chlorophenoxyacetic acid (MCPA) dosage, application timing and crop presence on the weed Cirsium arvense. Swedish farmers are recommended to control C. arvense chemically when most shoots are 10-20 cm tall, and mechanically at the compensation point (CP). Recent studies have shown that the CP occurs before shoots reach the three-leaf stage. We hypothesised that (i) herbicide application near the three-leaf stage gives the strongest control, (ii) crop presence increases herbicide effects, and (iii) a 50% herbicide dose gives the same effect as 100%. Treatments of the pot experiment consisted of MCPA 750; 0%, 50% and 100% of the recommended dose applied at leaf stages 3-8, with and without barley. The strongest control was obtained at four leaves and a maximum shoot height of 13 cm, using the recommended dose and with spring barley. In a field population, a maximum shoot height of 13 cm corresponded to a medium height of 6 cm. The 50% dose gave poorer control. Spraying with the recommended dose at the four-leaf stage reduced the development of C. arvense most effectively. Based on this, we recommend that herbicide spraying should be performed at earlier leaf stages/median heights than previously recommended.     

Tilth index: an approach to optimize tillage in rice–wheat system

This study was conducted to determine a tilth index from tillage induced soil physical properties and grain yield to optimize tillage in rice–wheat system. The experiment was conducted in a silty clay loam (Aquic hapludoll) associated with a shallow water table fluctuating between 0.02 and 0.96 m from the surface. Tillage treatments for rice were puddling by four passes of rotary puddler (PR), reduced puddling (ReP), conventional puddling (CP) and direct seeding without puddling (DSWP) in four replications. Tillage treatments for wheat were zero tillage (ZT) and conventional tillage (CT) superimposed over the plots of rice tillage treatments. Measurements were made of puddling index and specific volume (only in the rice season), bulk density, saturated hydraulic conductivity, infiltration rate, plasticity index, porosity and organic carbon in the rice and wheat seasons. Rice yield in the PR plots was highest and statistically equal to that in the ReP plots but wheat yield was highest in the DSWP plots under ZT condition and was statistically equal to that in the ReP plots.Tilth index (TI) was determined in two ways: one by the model suggested by Singh et al. [Trans. ASAE 35 (6) (1992) 1777] and the second by a proposed regression model. The proposed regression model utilizes soil physical properties having significant influence on crop yield. As per the Singh et al. model, wheat yield increased linearly with increasing TI from 0.75 to 0.89 but rice yield decreased with increasing TI from 0.67 to 0.81. Both TI and its relation with rice yield were contrary to their observations. The proposed regression model showed a value of TI in the range of 0.74–0.87 for rice soils and 0.86–1.0 for wheat soils as indicators of TI for optimum yields of rice and wheat. A high TI corresponds to low tillage both for rice and wheat. The optimum yield with minimum tillage operations coincided with TI obtained in ReP plots of rice and in ZT plots of wheat under ReP conditions. Results thus show that the quality of soil puddle obtained by half the efforts in PR and CP was sufficient for optimum yields of rice. Similarly, wheat sowing by zero-till drill in such a reduced puddling plots of rice was sufficient for optimum yields of wheat in Tarai soils associated with shallow water tables. The proposed regression model is simple and compatible to use in the existing crop growth models, such as in DSSAT 3.5, with suitable alterations.     

Development of an immunoassay for the residues of the herbicide bensulfuron-methyl

To develop a competitive indirect enzyme-linked immunosorbent assay based on polyclonal antibodies for the detection of the sulfonylurea herbicide bensulfuron-methyl, seven structurally related haptens were synthesized. Four of them mimicking the target analyte were conjugated to keyhole limpet hemocyanin by the N-hydroxysuccinimide activated ester method to use as immunogens, and all of them were conjugated to bovine serum albumin to use as plate-coating antigens. Polyclonal antibodies raised in rabbits and the coating antigens were screened and selected for the assay in simple homologous and heterologous ELISA formats. Three sensitive heterologous ELISAs were selected and optimized, showing the average IC(50) values of bensulfuron-methyl as low as 0.17, 0.09, and 0.09 ng/mL, the detection ranges of 0.04-0.60, 0.01-0.60, and 0.04-0.25 ng/mL, and the lowest detection limits of 0.03, 0.002, and 0.03 ng/mL, respectively. The cross-reactivities of other sulfonylurea herbicides and metabolites of bensulfuron-methyl to the antibodies were less than 15% in the two assays. Recoveries from the analyte-fortified water samples in assay I were in the range of 81-125% by simple dilution. The correlation between the ELISA and HPLC was 0.999 (n = 15) with a slope of 1.37 in the analysis of groundwater samples fortified with bensulfuron-methyl. The results obtained strongly indicate that the ELISA can be a highly sensitive and convenient tool for detecting bensulfuron-methyl residues in agricultural and environmental samples.     

Effects of the herbicide glyphosate on nitrogen cycling in an acid forest soil

The herbicide glyphosate was sprayed aerially on a section of conifer forest in Atlantic Canada that had been previously clearcut and reforested. Glyphosate was then tested for effects on ammonification, nitrification, and denitrification for a period of 8 months by comparing microbial activity in treated and untreated zones of the clay loam forest soil and the overlying decomposing litter, both with a pH of 3.8. With ammonification, there was generally a stimulation of activity in both the forest litter (FL) and forest soil (FS) that had been exposed to glyphosate during spraying. Nitrification rates in FL and FS were very low and glyphosate had no appreciable stimulatory or inhibitory effect on nitrification. Although glyphosate stimulated denitrification in a few instances, it generally had no significant effect on denitrification activity in FL and FS exposed during spraying. With all processes, microbial activity in FL was significantly greater than that in FS. Laboratory bioassays were also performed with FL and FS, as well as two silt loam (pH 5.8 and 6.4) and one sandy loam (pH 6.8) agricultural soils, using glyphosate concentrations up to 200 times higher than field application rates. With ammonification and denitrification, glyphosate generally stimulated activity at all levels tested and in all soil used. Glyphosate stimulated ammonification by 50% at concentrations ranging from 140 to 550 μg g^?1 for the soils and >4000 μg g^?1 for FL. With denitrification, the corresponding herbicide levels were approximately 2250 μg g^?1 for FS, > 10,000 for FL, and 450 for an agricultural soil. With nitrification, it was estimated that glyphosate concentrations greater than 1000 to 2000 μg g^?1 would be required to cause a 50% inhibition of activity. The careful use of glyphosate in forestry should have no toxic effects on N cycling in soils.     

Assisting nonsoil specialists to identify soil types for land management: an approach using a soil identification key and toposequence models

Conventional soil survey information is often unclear except to specialists. An approach using soil toposequences and a soil identification key was used to aid the translation of soil survey information into a form suitable for a nonspecialist audience with a case study from Brunei. Soil Taxonomy was used to characterize the major soil types; however, to assist end users, a complementary special‐purpose soil classification system was developed in the form of a soil identification key using plain language terms in English that were also translated into Malay. Easily recognized soil features such as depth, colour and texture were used to categorize soils to match Soil Taxonomy classes. To complement the soil identification key, conceptual soil toposequence models presented the soil distribution patterns in a visual format that local land users understood. Legacy soil survey information along with a widespread distribution of 172 soil sites from 35 traverses in 16 study areas provided a dataset to develop and test soil toposequence models and the soil identification key which both proved reliable and robust. The approach demonstrated in Brunei could be applied to other countries and landscapes.     

水稻雄蕊导管发育研究

本文以水稻粤泰保持系为材料，采用ATPase定位方法研究了单核至三核花粉期雄蕊导管的发育。单核边位花粉期，分化的导管胞质变浓厚、细胞核染色质浓缩、核转变为新月形并出现凋亡小体；此外，导管内物质也可以大分子形式直接撤离。单核边位晚期，雄蕊导管发育成熟。在二核和三核花粉期，导管内重新出现具有ATPase活性的物质，同样的现象也存在于农垦58s可育花药成熟导管中。以上结果暗示水稻雄蕊导管分化存在程序性死亡及非程序性死亡多种途径，水稻成熟导管内具有ATPase活性物质可能是一种普遍现象。     

Ozone pollution modifies the response of sugarbeet to the herbicide phenmedipham

Experiments were conducted in which sugarbeet plants (Beta vulgaris L. cv. Saxon) with 2 to 3 leaves were exposed to a simulated 2 day ozone episode (100 nl l^?1, 7 h d^?1). Three days later, the plants were sprayed with field rate phenmedipham (1.14 kg a.i. ha^?1) and growth analysis conducted 7 days later indicated an antagonistic interaction was occurring. Physiological and biochemical studies were undertaken to determine the nature of this antagonism. Treatment with phenmedipham increased the ratio of transpiration to photosynthetic rates within 2 days of spraying, whilst exposure to ozone had no effect. When the two treatments were combined, water use efficiency was not significantly different from that when phenmedipham was applied alone. In contrast, trends in the membrane permeability after treatment, indicated that the response of plants exposed to ozone followed by treatment with the herbicide, was intermediate between that of the herbicide (high permeability) and ozone (low permeability). Furthermore, when the two treatments were combined the results of antioxidant enzyme assays indicated greater than expected activities of enzymes which are mainly cytosolic, eg. guaiacol peroxidase, as well as a similar increase in the activity of the mainly chloroplastic superoxide dismutase. Treatment with ozone alone and phenmedipham alone only slightly increased superoxide dismutase. Ozone may therefore induce the activities of these protective enzymes. Thus, when another oxidative stress, such as the photosystem II inhibitor phenmedipham, was applied the plants could then respond more quickly and showed less herbicide visible damage.     

Source identification and apportionment of soil cadmium in cropland of Eastern China: a combined approach of models and geographic information system

Purpose

Cadmium (Cd) is regarded as one of the most toxic heavy metals in the environment and can undermine the ecosystem function and human health at trace level due to its high toxicity. In order to reduce the anthropogenic Cd input into agricultural soil, it is of utmost importance to pinpoint the sources of Cd in soils and apportion their respective contributions.

Materials and methods

One hundred twenty-seven topsoil samples and 21 subsoil samples were collected from croplands of Meishan Basin, Changxing County, Zhejiang Province, Eastern China, and analyzed for concentrations of Cd and other heavy metals. Finite mixture distribution model (FMDM) was employed to fit the data to obtain the local soil Cd threshold value, a critical indicator to assess soil heavy metal contamination. Then, principal component analysis (PCA) and geographic information system (GIS) were used to identify the potential sources of Cd. Finally, positive matrix factorization (PMF) was applied to apportion the source contributions.

Results and discussion

Among the 127 topsoil samples, 71 were subject to Cd contamination with a mean concentration of 0.66 mg kg^?1 while the others were considered as background with a lower mean concentration of 0.145 mg kg^?1, close to the local background concentration of 0.142 mg kg^?1. Further, three components were extracted by PCA and interpreted as natural background, lead-acid battery manufacturing plants, and construction material associated activities, respectively. Additionally, most of the topsoil samples around the lead-acid battery manufacturing plants, construction material plants, and limestone/marble quarries were classified as Cd contaminated. However, PMF failed to get a successful portioning.

Conclusions

Lead-acid battery manufacturing plants and construction material associated activities were the main anthropogenic sources of soil Cd contamination. With the help of FMDM, it is possible to distinguish the contaminated soil and estimate the contribution of anthropogenic sources to soil Cd. The apportionment by PMF was not successful in this paper due to the high skewness or outliers of Cd concentration in sampling sites and violation of the assumption that all samples have the same sources.

     

模糊故障树分析方法在HACCP中的应用研究

危害分析与关键控制点(HACCP)是一个复杂的系统工程,对于农产品加工企业或食品企业而言,制定一个产品的HACCP计划有很大的难度,特别是对于关键控制点的正确选取更需要领域专家的帮助。该文介绍了故障树分析方法在HACCP体系第一原则和第二原则上的应用,并引入模糊数学理论中的模糊算法和非模糊化方法与故障树分析方法相结合,分别适用于计划的制定和计划的变更,并可根据该方法开发出制定计划的软件工具,使得计划的制定趋于简单化和自动化。     

The spatial variability of soil nitrates in arable and pasture landscapes: implications for the development of geographical information system models of nitrate leaching

Abstract. In response to the European Community Nitrate Directive (91/676) a catchment scale Geographical Information System (GIS) model of nitrate leaching has been developed to map nitrate vulnerability and predict average weekly fluxes of nitrate from agricultural land units to surface water. This paper presents a pilot study which investigated the spatial variability of soil nitrates in order to: (1) define an appropriate pixel size for modelling N leaching; (2) quantify the within-unit variability of soil nitrate concentrations for pasture and arable fields; and (3) assist in the design of an efficient sampling strategy for estimating mean nitrate concentrations. Soil samples, taken from two 800 m transects in early September 1994, were analysed for water soluble nitrate. The arable soils had a mean nitrate-nitrogen concentration of 0.693 μg/g (S.E. 0.054 μg/g) and the pasture soils had a higher mean nitrate-nitrogen concentration of 0.86 μg/g (S.E. 0.085 μg/g). Spatial variability was investigated using variograms. The pasture data had a weak spatial relationship, whereas the arable data exhibited a strong spatial relationship which fitted a spherical variogram model (r² 0.87), with a range of 40 m. A pixel size of 40 m is suggested for nitrate modelling within the GIS based on the arable variogram and an improved sampling strategy for model validation is suggested, involving bulking sub-samples over a 40 m grid for estimating mean nitrate concentrations in combined land use and soil units.     

Diadromous fish conservation plans need to consider global warming issues: An approach using biogeographical models

Most of the European diadromous fish species are endangered and listed in the habitats fauna and flora directive, the bern convention and the IUCN Red List. Current conservation plans do not address global warming issues and consider the 1900 distribution range as the reference without taking into account the potential re-distribution of these species under global warming. However, for other taxa, predictive models have been used successfully to relate conservation assessment with the impact of global warming. We investigated the distribution of the various diadromous species regularly encountered in Europe, North Africa and the Middle East at the beginning of the 20th century. For each species, we related the observed distribution to a set of environmental variables describing the prevailing climate in the basins, the physical nature of the basins and reflecting historical events known to have affected freshwater fish distribution. We successfully built twenty-one accurate species-specific models out of twenty-eight during both the calibration and the validation phases. Longitude, a factor we interpret as related to biogeographical history, was selected in all models and temperature was included in fifteen models, in six it was the most explanatory variable. These models allowed us to separate the roles of ecology and history in explaining distribution patterns at species level. Historical events such as glaciations constrained the continental distribution of all diadromous species and six of these were also highly temperature-dependent. Based on these results, we claim that these models can be used to predict the potential distribution under changing climatic conditions and provide two relevant examples (i.e. for Alosa alosa and Pe tromyzon marinus). Predictive models could be useful as a preliminary tool to prepare long-term conservation plans on European, national and regional scales.     

我国湿地农业可持续发展模式探析

阐述了湿地农业内涵及不合理开发带来的湿地农业生态环境问题,探讨了我国3类典型湿地农业可持续发展模式,并提出发展对策     

DNOC, a model pollutant, adversely affects the potential of soil microbial communities to mineralise the herbicide 2,4-D: an investigation using micro-sampling procedures

The effects of the herbicide, DNOC, 4,6-dinitro-o-cresol, a model pollutant, have been studied by comparing the potential of soil microbial communities present in individual soil aggregates or in larger soil microcosms as samples of soil aggregates to mineralise the herbicide 2,4-D. We have shown that 2-3 mm soil aggregates vary widely in their 2,4-D mineralisation potential and that ageing or exposure to DNOC considerably simplified the distribution patterns of this capacity. The main factors of variation have been quantified and classified using a quasi-likelihood method derived from the Generalised Linear Model approach. Besides DNOC concentration and duration of exposure, an additional ‘rank’ factor reflecting a desiccation gradient of the aggregates on the microtiter plates was found to have statistical significance. We concluded that it should be possible to derive an experimental approach, designated as ‘functional profiling’, with potential use to detect soil chemical contamination. Curves of 2,4-D mineralisation in individual soil aggregates could be classified according to three different types of kinetics, which were assumed to reflect heterogeneous spatial distribution, differences in microbial community composition and varying efficiency of the microbial consortia involved in 2,4-D degradation. Exposure to DNOC considerably simplified the distribution patterns of the different types of kinetics with one type, showing slow rate and low cumulative mineralisation, becoming predominant as ageing, concentration and duration of DNOC exposure increased. We argue on the possible use of ‘kinetic profiling’ as a sensitive bioindicator of soil quality. By comparison, in soil microcosms, 2,4-D mineralisation showed an extra mineralisation potential of 64% over individual aggregates in the control soil and exposure to DNOC was followed by concentration and time-dependent recovery of the 2,4-D mineralisation potential. It is likely that 2 g size soil microcosms gather a larger number of biochemical capacities which could complement each other to increase the potential of soil to mineralise xenobiotic compounds.     

安徽大别山区退耕还林工程可持续发展模式

 对安徽大别山区生态环境特点、退耕还林的规模以及可持续经营模式等进行了分析。结果表明:安徽大别山区是个极其重要的水源涵养、水土保持功能区,适度退耕还林有利于保障7大水库和淠史杭灌区发挥长期效益、促进社会经济可持续发展;库区可适当扩大退耕还林规模,而在非库区,因人口稠密不应追求退耕还林规模;退耕还林工程的实施应注重模式选择和农民增收,实现大别山区社会经济可持续发展。