Herbicidal activity of slow-release herbicide formulations in wheat stands infested by weeds

The present study reports the herbicidal activity of metribuzin and tribenuron-methyl embedded in the degradable matrix of natural poly-3-hydroxybutyrate [P(3HB)/MET and P(3HB)/TBM]. The developed formulations were constructed as films and microgranules, which were tested against the weeds such as white sweet clover Melilotus albus and lamb's quarters Chenopodium album in the presence of soft spring wheat (Triticum aestivum, cv. Altaiskaya 70) as the subject crop for investigation. The activity was measured in laboratory scale experiments by determining the density and weight of the vegetative organs of weeds. The study was also aimed at testing the effect of the experimental formulation on the growth of wheat crop as dependent on the method of herbicide delivery. The experimental MET and TBM formulations showed pronounced herbicidal activity against the weed species used in the study. The effectiveness of the experimental formulations in inhibiting weed growth was comparable to and, sometimes, higher than that of the commercial formulations (positive control). The amount of the biomass of the wheat treated with the experimental herbicide formulations was significantly greater than that of the wheat treated with commercial formulations.     

Mobility and efficacy of 2,4-D herbicide from slow-release delivery systems based on organo-zeolite and organo-bentonite complexes

This research aimed to develop slow-release formulations (SRFs) of 2,4-dichlorophenoxyacetic acid (2,4-D) using zeolite and bentonite minerals modified with cetyltrimethylammonium (CTMA) surfactant. Adsorption–desorption, greenhouse bioassay and column experiments were carried out to assess the potential of the SRFs to control weeds while reducing the herbicide leaching losses to deep layers of soil. The results showed that only 6.5 mmol 2,4-D kg^?1 was retained by Na-bent, and the herbicide was not adsorbed by Na-zeol at all. The surface modification with CTMA surfactant, however, improved the 2,4-D adsorption capacity of the zeolite and bentonite up to 207.5 and 415.8 mmol kg^?1, respectively. The synthesized organo-minerals slowly released the retained 2,4-D discharging 22 to 64% of the adsorbed 2,4-D to the solution phase within 7 days. The SRFs significantly (P = 0.05) reduced the herbicide mobility within the soil columns keeping a great portion of the herbicide active ingredient in the upper 5 cm soil layer. The SRFs were significantly (P = 0.05) as effective as the free technical herbicide in weed control without harming the ryegrass as the main plant. Therefore, the synthesized SRFs could be considered as useful tools for weed control in sustainable agriculture.     

Ozone exposure of field-grown winter wheat affects soil mesofauna in the rhizosphere

A 2-year open-top chamber experiment with field-grown winter wheat (Triticum aestivum L. cv. Astron) was conducted to examine the effects of ozone on plant growth and selected groups of soil mesofauna in the rhizosphere. From May through June in each year, plants were exposed to two levels of O₃: non-filtered (NF) ambient air or NF+ 40 ppb O₃ (NF+). During O₃ exposure, soil sampling was performed at two dates according to different plant growth stages. O₃ exposure reduced above- and below-ground plant biomass in the first year, but had little effect in the second year. The individual density of enchytraeids, collembolans and soil mites decreased significantly in the rhizosphere of plants exposed to NF+ in both years. Differences were highest around anthesis, i.e. when plants are physiologically most active. The results suggest that elevated O₃ concentrations may influence the dynamic of decomposition processes and the turnover of nutrients.     

Impacts of ozone on the growth and yield of field-grown winter wheat

Seed of winter wheat (Triticum aestivum L. cv Riband) was sown on 29 August 1992 in eight field plots. Four plots were exposed to elevated ozone (O(3)) concentrations on 16 days between 29 August and 2 October 1992, for 6 h day(-1), and on 27 days between 29 March and 24 August 1993, for 7 h day(-1). Mean daily O(3) concentrations were approximately 30 and 80 nmol mol(-1) in ambient and fumigated plots, respectively. Plants were sampled on 5 November (1992), 14 January, 16 February, 1 April, 25 May, 23 June and 24 August (1993). No visible symptoms of O(3) damage or premature senescence were observed at any time over the course of the experiment. Exposure to elevated O(3) decreased the above ground biomass by reducing plant density and individual plant relative growth rate. However, there was no significant influence of the pollutant on the growth of the root relative to the shoot. Assessment of yield characteristics at the final harvest revealed an O(3)-induced decrease in the number of grains per ear, as a result of fewer grains per spikelet and an increase in the number of infertile florets per spikelet. No significant effects of the pollutant on the number of ears per plant, spikelets per ear, or 1000 grain weight were found. As a result of the combined effects on the number of grains per ear and the decrease in plant density and growth rate, O(3) exposure reduced grain and straw yields (tonnes ha(-1)) by 13 and 8%, respectively. However, no significant change in the partitioning of dry matter between the grain and the straw was observed in fumigated plots. The findings are discussed within the context of United Nation Economic Commission for Europe critical level guidelines for the protection of crop yields, in relation to their application to winter-sown crops.     

Whole leaf fluorescence as a quantitative probe of detoxification of the herbicide chlortoluron in wheat

Six varieties of wheat, tolerant or susceptible towards chlortoluron, a photosynthesis-inhibiting herbicide, were submitted to a 24-hour herbicide treatment. Fluorescence induc tion kinetics of whole leaves were recorded during the six following days. Recovery of photosynthetic electron transfer was found in tolerant varieties only. Ratios of I and P levels of induction kinetics appeared as the most reliable parameter for quantitative evaluation of detoxification rates.     

Metabolism of the14C-labeled herbicide clodinafop-propargyl in plant cell cultures of wheat and tobacco

The metabolism of ¹⁴C-clodinafop-propargyl (CfP) was examined in cell cultures of wheat (Triticum aestivum L. cv. ‘Heines Koga II’) and tobacco (Nicotiana tabacum L.). Besides the non-transgenic tobacco culture, cultures transformed separately with cDNA of human cytochrome P450-monooxygenases (P450s) CYP1A1, CYP1A2, CYP3A4, CYP2B6 and CYP2C19 were examined. Experiments with wheat were executed in the presence and absence of safener cloquintocet-mexyl (CqM). After 48 h of incubation, only about 10% of applied ¹⁴C was found in media (both tobacco and wheat). Non-extractable residues of ¹⁴C-CfP in wheat cells were 16.54% (without CqM) and 30.87% (with CqM). In all tobacco cultures, 82.41–92.46% of applied radioactivity was recovered in cell extracts. In contrast to wheat, non-extractable residues amounted only to 1.50–2.82%. As determined by radio-thin layer chromatography (TLC) and -high-performance liquid chromatography (HPLC), the parent CfP was not found in the cell extracts of wheat; in tobacco cell extracts, only traces of CfP were detected. After a hydrolysis of assumed carbohydrate conjugates of CfP derived polar ¹⁴C-labeled compounds, TLC and HPLC analysis showed that in wheat, a more complex pattern of metabolites of CfP were observed as compared to all tobacco cultures. In hydrolysates resulting from wheat, the identity of three primary products was confirmed by means of GC-EI-MS: free acid clodinafop (Cf), hydroxy-Cf hydroxylated at the pyridinyl moiety, and 4-(5-chloro-3-fluoropyridin-2-yloxy)phenol. In hydrolysates derived from all tobacco cultures, main metabolite was Cf besides only traces of further unidentified products. Differences among the different tobacco cultures (non-transgenic, transgenic) did not emerge. According to kinetics of disappearance of primary metabolite Cf as well as formation of polar soluble products and non-extractable residues, metabolization of CfP proceeded at a noticeably higher rate in wheat cells treated with safener CqM than in cells without CqM treatment. Thus, these results indicated a stimulation of CfP's metabolism by CqM, although metabolic profiles observed in CqM treated and non-treated cells (after hydrolysis) were qualitatively similar. The findings obtained from all tobacco cultures suggested that with the exception of ester cleavage to Cf, CfP cannot be metabolized by tobacco itself or by the human P450s examined.     

Biological responses of wheat (Triticum aestivum) plants to the herbicide chlorotoluron in soils

Chlorotoluron is a phenylurea herbicide that is widely used for controlling grass weeds in the land of cereal, cotton and fruit production. However, extensive use of this herbicide may lead to its accumulation in ecosystems, thus inducing the toxicity to crops and vegetables. To assess chlorotoluron-induced toxicity in plants, we performed the experiment focusing on the metabolic adaptation of wheat plants (Triticum aestivum) to the chlorotoluron-induced oxidative stress. The wheat plants were cultured in the soils with chlorotoluron at concentrations of 0-25mg/kg. Chlorotoluron accumulation in plants was positively correlated with the external chlorotoluron concentrations, but negatively with the plant growth. Treatment with chlorotoluron induced the accumulation of O(2)(-) and H(2)O(2) in leaves and resulted in the peroxidation of plasma membrane lipids in the plant. We measured the endogenous proline level and found that it accumulated significantly in chlorotoluron-exposed roots and leaves. To understand the biochemical responses to the herbicide, activities of the antioxidant enzymes, such as superoxide dismutase (SOD), peroxidase (POD), catalase (CAT) and ascorbate peroxidase (APX) were assayed. Analysis of SOD activity by non-denaturing polyacrylamide gel electrophoresis (PAGE) revealed that there were three isoforms in the roots and leaves, but the isoforms in the tissues showed different patterns. Also, using the native PAGE, 6 isoforms of root POD and 10 in leaves were detected. The total activity of POD in roots was significantly enhanced. Activities of APX in roots and leaves showed a similar pattern. The CAT activities were generally suppressed under the chlorotoluron exposure.     

Constructing herbicide metribuzin sustained-release formulations based on the natural polymer poly-3-hydroxybutyrate as a degradable matrix

Polymer poly(3-hydroxybutyrate) [P(3HB)] has been used as a matrix in slow-release formulations of the herbicide metribuzin (MET). Physical P(3HB)/MET mixtures in the form of solutions, powders, and emulsions were used to construct different metribuzin formulations (films, granules, pellets, and microparticles). SEM, X-Ray, and DSC proved the stability of these formulations incubated in sterile water in vitro for long periods of time (up to 49 days). Metribuzin release from the polymer matrix has been also studied. By varying the shape of formulations (microparticles, granules, films, and pellets), we were able to control the release time of metribuzin, increasing or decreasing it.     

Effects of ozone on the grain composition of spring wheat grown in open-top field chambers

In a three-year study carried out at a rural site in Switzerland, spring wheat (Triticum aestivum L. cv. Albis) was exposed to different levels of ozone (O(3)) in open-top-field chambers from the two-leaf stage until harvest. Field plots in ambient air (AA) were used for comparison. Grain recovered from the different treatments was analyzed for minerals (Ca, Mg, K, P), starch, protein, amino acids and alpha-tocopherol, in order to investigate the effect of O(3) on grain composition. Chamber-enclosure had small effects on some parameters (K, protein), but not on others (starch), as shown by the comparison of data from the AA and non-filtered-air treatment (NF). Differences between NF and charcoal-filtered air (CF) were very small. At O(3) concentrations higher than in the NF treatment (O(3)-1 = 1.5xNF and O(3)-2 = 2.5xNF), mineral contents were higher than in the NF and CF treatments. Protein content was increased only in the O(3)-2 treatment. Starch contents decreased from about 63% in the CF treatment to 54% in the O(3)-2 tratment. No effect of O(3) on the content of alpha-tocopherol and on the essential amino acid index of the protein was observed. It is concluded that compositional changes in wheat grain in response to O(3) are minor, and that ambient O(3) is not likely to cause important changes.     

Effects of herbicide stress on wheat cultivars from organic and conventional cropping systems

Abstract

Wheat (Triticum aestivum L.) seedlings grown from seeds produced in “organic”; (non‐chemical) and “conventional”; cropping systems are characterized by a) similar rates of root and shoot growth, b) equal sensitivity to phytotoxicity by the herbicide glyphosate, and c) equivalent basal activity of the enzyme glutathione S‐transferase (both in the roots and in the shoots). In addition, treatment of these seedlings with glyphosate leads to significantly higher contents of this enzyme both in the shoots and in the roots. However, time‐course and dose‐response investigations indicate significant differences in the induction pattern of glutathione S‐transferase: the response of “conventional”; wheat seedlings takes place earlier and with higher efficiency, than that of the “organic”; ones.     

石河子市春季大气颗粒物TSP和PM10中微生物群落特征

近来,有研究指出颗粒物中携带导致人类过敏、呼吸系统疾病或其他类疾病的微生物,其对公众健康的影响因为研究较少而一直被低估。采用16S rDNA、18S rDNA测序方法对石河子市2015年春季TSP和PM10污染物中细菌、真菌的群落结构特征进行研究。结果表明：在门的水平上,变形菌门（Proteobacteria）和放线菌门（Actinobacteria）是石河子市春季TSP和PM10中细菌的主要菌群,子囊菌门（Ascomycota）和担子菌门（Basidiomycota）是真菌的主要菌群。在属水平上,马赛菌属（Massilia）和不动杆菌属（Acinetobacter）在16S rDNA测序结果分析中相对含量较多,格孢腔菌属（Pleospora）和Penidiella在18S rDNA测序结果分析中相对丰度较高,仍然发现了一些可能导致人类及植物患病的菌属,期望此研究结果为人类生活提供参考。     

Assessment of the effects of herbicide spray drift on a range of plant species of conservation interest

With increasing use of herbicides there has been growing concern that spray drift from treated land will affect vegetation on adjacent nature reserves and other areas of high conservation interest. A preliminary attempt was made to assess this risk by placing a range of native plant species at different distances downwind from standardised drift events and assessing lethal effects and sublethal damage. Five herbicides were tested: asulam, 'Finesse' (chlorsulfuron + metsulfuron-methyl), glyphosate, MCPA and mecoprop. Applications were made at the appropriate time of years for each herbicide (autumn, spring and summer), and at both low and high wind speeds. The maximum safe distance at which no lethal effects were found was 6 m from the sprayer, but for most herbicides the distance was 2 m or less. Generally, damage symptoms were found at greater distances than lethal effects, but in most cases there was rapid recovery by the end of the growing season. These observations are consistent with drift-deposition models, in which the fallout of herbicide droplets has been measured. It is suggested that buffer zones surrounding nature reserves should be in the order of 5-10 m for ground sprayers to minimise the risk of herbicide impacts on these habitats.     

Persistence of herbicide fenoxaprop ethyl and its acid metabolite in soil and wheat crop under Indian tropical conditions

The persistence of fenoxaprop ethyl {Ethyl (RS)-2-[4-(6-chloro-1,3-benzoxazol-2-yloxy) phenoxy] propionate} herbicide and its active metabolite fenoxaprop acid was investigated in soil and wheat crop. Fenoxaprop acid was prepared by alkaline hydrolysis of fenoxaprop ethyl. A HPLC method was developed in which fenoxaprop ethyl herbicide and its acid metabolite showed sharp single peak at 6.44 and 2.61 min respectively. The sensitivity of the method for ester and acid was 2 and 1 ng respectively with limit of detection of 0.1 and 0.05 μg mL^?1. The recovery of fenoxaprop ethyl and fenoxaprop acid from soil, wheat straw and grain ranged between 73.8–80.2%. In a field experiment fenoxaprop ethyl (Puma super® 10 EC) when applied to wheat crop at the rate of 120 g and 240 g a.i. ha^-1 as post emergence spray, fenoxaprop ethyl converted to fenoxaprop acid. Residues of fenoxaprop ethyl and acid dissipated in soil with a half-life of 0.5 and 7.3 days, respectively. At harvest no detectable residues of fenoxaprop ethyl or acid were observed in soil, wheat grain and straw samples.     

Assessment of yield losses in tropical wheat using open top chambers

The present study deals with the evaluation of effects of ambient gaseous air pollution on wheat (Triticum aestivum L. var. HUW-234) growing in a suburban area situated in eastern Gangetic plain of India, using open top chambers. Eight hourly air monitoring was conducted for ambient concentrations of SO₂, NO₂ and O₃ in filtered chambers (FCs), non-filtered chambers (NFCs) and open plots (OPs). Various morphological, physiological and biochemical parameters were assessed during different developmental stages and finally yield parameters were quantified at the time of harvest.Mean concentrations of SO₂, NO₂ and O₃ were 8.4, 39.9 and 40.1 ppb, respectively during the experiment in NFCs. Concentrations of SO₂, NO₂ and O₃ reduced by 74.6%, 84.7% and 90.4%, respectively in FCs as compared to NFCs. Plants grown in FCs showed higher photosynthetic rate, stomatal conductance, chlorophyll content and Fv/Fm ratio as compared to the plants in NFCs and OPs. Lipid peroxidation, proline, total phenol and ascorbic acid contents and peroxidase activity were higher in plants grown in NFCs. There were improvements in morphological parameters of plants growing in FCs as compared to those in NFCs and OPs. Yield of plants also increased significantly in FCs as compared to those ventilated with ambient air (NFCs) or grown in OPs. During the vegetative phase, NO₂ concentrations were higher than O₃, but O₃ became dominant pollutant during the time of grain setting and filling. The study concludes that O₃ and NO₂ are the main air pollutants in the sub-urban areas causing significant yield reductions in tropical wheat plants.     

Persistence,mobility, efficacy and activity of chloroacetanilide herbicide formulation under greenhouse and field experiments

Persistence, stability, mobility and activity characteristics of organoclay and commercial formulation of alachlor were evaluated in soil columns and field plots in Gaza, Palestine. Relative concentrations of alachlor were accumulated in the top soil as determined by bioassay and consequently its mobility was retarded in soil treated with organoclay formulation. Alachlor applied as commercial EC formulation readily distributed through the soil media to a deeper depth. The herbicidal activity of alachlor applied as organoclay formulation was limited to the top soil whereas it disappeared from the top soil in plots treated with EC commercial formulation. Greenhouse and field experiments showed persistence, reduced mobility, safe and effective herbicide formulation at a significantly reduced applied rate when alachlor was applied as organoclay formulation.     

Determination of the herbicide fluroxypyr in oil matrices

The purpose of this study was to develop a method for the determination of fluroxypyr (4-amino-3,5-dichloro-6-fluro2-pyridyloxyacetic acid) residue in palm oil namely crude palm oil (CPO) and crude palm kernel oil (CPKO). The method involves the extraction of the herbicide from the oil matrix followed by low temperature precipitation and finally quantification of the residues using the high performance liquid chromatography (HPLC). The extraction efficiency of the method was evaluated by conducting recovery studies. The recovery of fluroxypyr from the fortified CPO samples ranged from 78%–111% with the relative values for the coefficient of variation ranging from 1.4 to 8.6%. Furthermore, the recovery of fluroxypyr from the spiked CPKO samples ranged from 91–107% with the relative values for the coefficient of variation ranging from 0.6 to 4.5%. The minimum detection limit of fluroxypyr in CPO and CPKO was 0.05 μg/g. The method was used to determine fluroxypyr residues from the field-treated samples of CPO and CPKO. When fluroxypyr was used for weed control in oil palm plantations no residue was detected in CPO and CPKO irrespective of the sampling interval and the dosage applied at the recommended or double the manufacturer's recommended dosage.     

Determination of the herbicide fluroxypyr in oil matrices

The purpose of this study was to develop a method for the determination of fluroxypyr (4-amino-3,5-dichloro-6-fluro2-pyridyloxyacetic acid) residue in palm oil namely crude palm oil (CPO) and crude palm kernel oil (CPKO). The method involves the extraction of the herbicide from the oil matrix followed by low temperature precipitation and finally quantification of the residues using the high performance liquid chromatography (HPLC). The extraction efficiency of the method was evaluated by conducting recovery studies. The recovery of fluroxypyr from the fortified CPO samples ranged from 78%-111% with the relative values for the coefficient of variation ranging from 1.4 to 8.6%. Furthermore, the recovery of fluroxypyr from the spiked CPKO samples ranged from 91-107% with the relative values for the coefficient of variation ranging from 0.6 to 4.5%. The minimum detection limit of fluroxypyr in CPO and CPKO was 0.05 microg/g. The method was used to determine fluroxypyr residues from the field-treated samples of CPO and CPKO. When fluroxypyr was used for weed control in oil palm plantations no residue was detected in CPO and CPKO irrespective of the sampling interval and the dosage applied at the recommended or double the manufacturer's recommended dosage.     

The sensitivity of soil enzymes,microorganisms and spring wheat to soil contamination with carfentrazone-ethyl

Herbicides pose a significant threat to the natural environment, in particular in soils that are most exposed to plant protection agents. Prolonged herbicide use leads to changes in soil metabolism and decreases soil productive potential. In this study, the influence of carfentrazone-ethyl (CE) on the microbiological and biochemical properties of soil and the yield of Triticum aestivum L. was evaluated. Carfentrazone-ethyl was applied to sandy loam (pH_KCl – 7.0) in doses of 0.000, 0.264, 5.280, 10.56, 21.18, 42.24, 84.48 and 168.96 µg kg^?1 DM soil. Soil samples were subjected to microbiological and biochemical analyses on experimental days 30 and 60. Carfentrazone-ethyl disrupted the biological equilibrium in soil by decreasing the abundance and biodiversity of soil-dwelling microorganisms, the activity of soil enzymes, the values of the biochemical activity indicator and spring wheat yields. Carfentrazone-ethyl had the most adverse effects when applied in doses many fold higher than those recommended by the manufacturer. The toxic effects of CE were also determined by its soil retention time. Soil treated with CE was characterized by higher counts of oligotrophic bacteria, organotrophic bacteria, bacteria of the genus Azotobacter, actinomycetes and fungi on day 60, and spore-forming oligotrophic bacteria on day 30. The activity of dehydrogenases, urease, alkaline phosphatase and β-glucosidase was higher on day 30 than on day 60.     

Assessment of the photochemistry of OH and NO3 on Jeju Island during the Asian-dust-storm period in the spring of 2001

In this study, we examined the influence of the long-range transport of dust particles and air pollutants on the photochemistry of OH and NO3 on Jeju Island, Korea (33.17 degrees N, 126.10 degrees E) during the Asian-dust-storm (ADS) period of April 2001. Three ADS events were observed during the periods of April 10-12, 13-14, and 25-26. Average concentration levels of daytime OH and nighttime NO3 on Jeju Island during the ADS period were estimated to be about 1x10(6) and 2x10(8) moleculescm(-3) ( approximately 9 pptv), respectively. OH levels during the ADS period were lower than those during the non-Asian-dust-storm (NADS) period by a factor of 1.5. This was likely to result from higher CO levels and the significant loading of dust particles, reducing the photolysis frequencies of ozone. Decreases in NO3 levels during the ADS period was likely to be determined mainly by the enhancement of the N2O5 heterogeneous reaction on dust aerosol surfaces. Averaged over 24 h, the reaction between HO2 and NO was the most important source of OH during the study period, followed by ozone photolysis, which contributed more than 95% of the total source. The reactions with CO, NO2, and non-methane hydrocarbons (NMHCs) during the study period were major sinks for OH. The reaction of N2O5 on aerosol surfaces was a more important sink for nighttime NO3 during the ADS due to the significant loading of dust particles. The reaction of NO3 with NMHCs and the gas-phase reaction of N2O5 with water vapor were both significant loss mechanisms during the study period, especially during the NADS. However, dry deposition of these oxidized nitrogen species and a heterogeneous reaction of NO3 were of no importance.