Optimization and validation of the solid-liquid extraction technique for determination of picloram in soils by high performance liquid chromatography

The objective of this study was to optimize and validate the solid-liquid extraction (ESL) technique for determination of picloram residues in soil samples. At the optimization stage, the optimal conditions for extraction of soil samples were determined using univariate analysis. Ratio soil/solution extraction, type and time of agitation, ionic strength and pH of extraction solution were evaluated. Based on the optimized parameters, the following method of extraction and analysis of picloram was developed: weigh 2.00 g of soil dried and sieved through a sieve mesh of 2.0 mm pore, add 20.0 mL of KCl concentration of 0.5 mol L-1, shake the bottle in the vortex for 10 seconds to form suspension and adjust to pH 7.00, with alkaline KOH 0.1 mol L-1. Homogenate the system in a shaker system for 60 minutes and then let it stand for 10 minutes. The bottles are centrifuged for 10 minutes at 3,500 rpm. After the settlement of the soil particles and cleaning of the supernatant extract, an aliquot is withdrawn and analyzed by high performance liquid chromatography. The optimized method was validated by determining the selectivity, linearity, detection and quantification limits, precision and accuracy. The ESL methodology was efficient for analysis of residues of the pesticides studied, with percentages of recovery above 90%. The limits of detection and quantification were 20.0 and 66.0 mg kg-1 soil for the PVA, and 40.0 and 132.0 mg kg-1 soil for the VLA. The coefficients of variation (CV) were equal to 2.32 and 2.69 for PVA and TH soils, respectively. The methodology resulted in low organic solvent consumption and cleaner extracts, as well as no purification steps for chromatographic analysis were required. The parameters evaluated in the validation process indicated that the ESL methodology is efficient for the extraction of picloram residues in soils, with low limits of detection and quantification.

Mefenpyr-diethyl action on fenoxaprop-p-ethyl detoxification in wheat varieties

Safeners protect crops against herbicide injury. The aim of this study was to examine the differential susceptibility of five wheat (Triticum aestivum) varieties to the herbicide fenoxaprop-p-ethyl, as well as the performance of mefenpyr-diethyl on minimizing herbicide injury and on lipid contents. Varieties BRS 49, CD 104, CEP 24, IAPAR 78 and Rubi were sprayed with fenoxaprop-p-ethyl (69 g ha¹), fenoxaprop-p-ethyl + mefenpyr-diethyl (69 g + 18.75 g ha-1), or mefenpyr-diethyl (18.75 g ha-1). Plants were evaluated visually for injury at 7 and 14 days after treatment (DAT). Glutathione S-transferase (GST) activity was assayed in aerial parts at 7 DAT, and lipid content was measured at 14 DAT. Varieties CEP 24, IAPAR 78 and Rubi were more tolerant to fenoxaprop-p-ethyl than BRS 49, and CD 104 rapidly recovering from the slight phytotoxicity symptoms produced by the herbicide. Mefenpyr-diethyl prevented crop injury associated with the herbicide. GST activity did not correlate directly with fenoxaprop-p-ethyl detoxification. However, lipid content was related to the susceptibility of wheat to fenoxaprop-p-ethyl treatment.

Use of herbicides on turfgrass

In crop production, weeds must be controlled so as not to adversely affect crop yield and crop quality. Thus, a low level of weeds infesting a field, in most instances, is not a problem. Except in sod or seed production, turfgrass does not have a yield component. The value of turfgrass is its inherent aesthetic quality and usability. Aesthetic quality is the beauty and value that turfgrass adds to a managed landscape. Usability can be the durability of a sport field, trueness of golf putting green roll, or reduction in soil loss from water runoff or wind. Any weed presence in turfgrass can decrease the aesthetic quality and usability of turfgrass. Utilizing herbicides is the only way to completely control weeds in a turfgrass stand. While it is possible to reduce weed populations using cultural or mechanical management practices, it is impossible to completely eliminate weeds as can be accomplished with herbicides. This manuscript will review the major herbicides used in turfgrass in the United States with respect to their modes of action, herbicide family, and primary use in turfgrass.

Growth inhibitors in turfgrass

Well-maintained lawns are comfortable and safe places for leisure activities and sports practice, and they also bring environmental benefits; for example, they reduce soil exposure to erosion and releases atmospheric CO2, thus reducing the greenhouse effect. However, regardless of the purpose of use or the choice of the plant species to form the lawn, the highest costs involve cutting that is needed to keep the turfgrass at its appropriate height. Successive lawn cutting operations are necessary basically because of the vegetative and reproductive growth of turfgrass which, in Brazil, occurs mainly from October to March. Expenditures with successive mechanical cuttings have fostered the search of alternative procedures to keep lawn plants at appropriate height, such as the use of plant growth inhibitors, an increasingly interesting procedure. Since the use of this technology in Brazil is still at its early stage, the aim of this literature review is to examine aspects associated with lawn management by using growth inhibitors. Another alternative is to increase the knowledge of the classification and rational application of the different compounds currently available in the market.

Sorption of fomesafen in Brazilian soils

The study of the dynamics of a herbicide in the soil focus on the interactions with environmental components to obtain agronomic efficiency, ensuring selectivity to the culture and risk reduction of environmental impact. This study evaluated the sorption process of fomesafen in the Brazilian soils Ultisol, Cambisol, and Organosol. Besides soil, washed sand was used as an inert material for determination of the sorption ratio of fomesafen in the soil. The bioassay method was applied, using Sorghum vulgare plants as bio-indicator of herbicide presence. Plant poisoning evaluation and harvest for dry matter determination were carried out 21 days after sorghum sowing. To calculate C50, the nonlinear log-logistic model was applied and sorption ratios of the herbicide were obtained in different soils. The decreasing sorption ratio of formesafen in the soils was: Organosol > Ultisol > Cambisol. It was concluded that the contents of organic matter and clay in the soils were the attributes that most influenced fomesafen sorption.

Directed-spray application of paraquat and diuron in physic nut plants

There is little information about the selectivity of herbicides in physic nut (Jatropha curcas) in Brazil. Therefore, this study aimed to evaluate the selectivity of different doses and mixtures of paraquat and diuron in direted-spray applications in physic nut plants in greenhouse conditions. The study used a randomized block design, with five replicates. The treatments were: paraquat (200 and 600 g ha-1), diuron (1,000 and 2,000 g ha-1), paraquat + diuron (200 + 1,000 g ha-1), paraquat + diuron (200 + 2,000 g ha-1), paraquat + diuron (600 + 1,000 g ha-1), paraquat + diuron (600 + 2,000 g ha-1) and a control (no application). Directed-spray application was performed at 70 days after sowing by the lower third of the plants. The treatments of diuron and paraquat + diuron mixtures affected the growth and photosynthetic activity of physic nut plants, injuries being more pronounced at doses of diuron of 2,000 g ha‑1, while the isolated application of paraquat at doses of 200 and 600 g ha-1 showed good selectivity potential for physic nut plants.

Chemical control of Pileamicrophylla in cattleya seedlings (Cattleyatenebrosa x Cattleyaleopoldy)

Species of the orchidaceae family are grown for marketing flowers and among them the genus Cattleya stands out. However, due to its slow growth, the substrate is subjected to weed infestation. Therefore, this study aims to evaluate the selectivity and efficiency of herbicides in controlling Pilea microphylla in Cattleya orchid seedlings (Cattleya tenebrosa x Cattleya leopoldy). We used a completely randomized design with four replications. The evaluated herbicides were oxyfluorfen (0, 120, 240 and 480 g ha-1), flumioxazin (0, 12.5, 25 and 40 g ha-1), nicosulfuron (0, 20, 40 and 80 g ha-1) mesotrione (0, 96, 144 and 192 g ha-1), clethodim (0, 60, 84 and 108 g ha-1) and metsulfuron-methyl (0, 1.2, 1.8 and 2.4 g ha-1). At post-emergence applying time, the Cattleya plants had three bulb sand were 10 cm tall, while P. microphylla, where 5 cm tall. Nicosulfuron, mesotrione and clethodim herbicides did not control P. microphylla, while oxyfluorfen and flumioxazin showed over 90% efficiency level sin controlling P. microphyllafrom 14 days after application (DAA). As to metsulfuron-methyl, it showed efficiency superior to 90% from the control dose of 1.8 g ha-1 at 28 DAA. All herbicides were selective plants of Cattleya, however, only oxyfluorfen, flumioxazin and metsulfuron-methyl were effective in controlling P. microphylla.

How glyphosate may affect transgenic soybean in different soil and phosphorus levels

The technology that employs genetic modifications brought a significant increase in the utilization of glyphosate. Transgenic soybean has been suffering injury, even though it possesses a resistance mechanism to glyphosate. Currently, there are only a few studies on the dynamics of glyphosate in transgenic soybean planted in soils with different textures interacting with phosphorus concentrations. This study focused on assessing the effects of glyphosate in transgenic soybean plants on different types of soil and at different phosphorus levels. The experimental design was completely randomized, in factorial design: 2 x 6 x 3, that being 2 soil types, 6 doses of glyphosate and 3 levels of phosphorus, and four replications. Plants were cultivated for thirty days in pots with two types of soil, one being clayey (Red-Yellow Latosol) and the other sandy (Quartzarenic Neosol). They received one, two, and three times the maintenance dose of fertilization of phosphorus, corresponding to: 170, 250 and 330 kg of P2O5 ha-1 to QN, and 380, 460 and 540 kg P2O5 ha-1 to RYL, respectively. Glyphosate was applied at six different doses: 0, 1,200, 2,400, 12,000, 60,000 and 120,000 g ha-1 of active ingredient. Plant height, a and b chlorophyll, and shoot were lower for the plants that received lower doses of glyphosate, regardless of the type of soil. Greater availability of phosphorus and lower amount of glyphosate used in Quartzarenic Neosol soil provided for less phytointoxication symptoms in transgenic soybean.

Application of Sulfentrazone in Stages of Germination of IAC 90 Cassava Cuttings in Clay Soils and Sandy

Weeds interfere dramatically in the productive potential of cassava; however, information regarding herbicides that are selective to crops is still scarce. Thus, the aim in this study was to assess the initial growth of IAC 90 cassava plants after the application of sulfentrazone at different stages of germination of cassava in clayey and sandy soils. Three experiments were simultaneously deployed: the first experiment consisted in the application of sulfentrazone in the non-germinated stage of cassava cuttings; the second one in the stage of germinated cassavas cuttings (0.9 cm shoots); and the third one in applications in the stage of cassava cuttings with buds emerging (6.5 cm shoots and emerging from the soil). For each experiment the experimental design in randomized blocks was used in the 2 x 5 factorial arrangement with four replications. The factors were composed of two soils (sandy and clayey) and five doses of sulfentrazone (0, 250, 500, 750 and 1,000 g ha-1). It was found that depending on the herbicide dose, development stage of the buds of cassava cuttings and the type of soil, damage can occur in the initial development of the IAC 90 cassava plants. The greatest potential of sulfentrazone selectivity has occurred in applications in the non-germinated cassava cuttings stage and in doses lower than 500 g ha-1 in the clayey soil.

SELECTION OF HERBICIDES TARGETING THE USE IN CROP SYSTEMS CULTIVATED WITH SHOWY CROTALARIA

ABSTRACT The increase in the area planted with Crotalaria spectabilishas occurred by several factors, highlighting the potential to reduce the nematodes, nitrogen fixation and the high production of biomass. By becoming a species sown as a crop, it is necessary to control the weeds that coexist with showy crotalaria. This change in the use of this crop creates the possibility of this specie becoming a weed. The aim of this study was to assess the potential use of herbicides applied in preemergence and postemergence of C.spectabilisfor different purposes (control of volunteer and selectivity plants). Three experiments were installed in a greenhouse (two with herbicides applied in preemergence - in soils with distinct textural categories; and one experiment with herbicides applied in postemergence). The results of the experiments with herbicides applied in preemergence showed that: amicarbazone, atrazine, diuron, metribuzin, prometryn, fomesafen and sulfentrazone showed effectiveness for control of C.spectabilis in clayey soil. Besides these, flumioxazin and isoxaflutole also showed potential to be used in the control of showy crotalaria in soils with loam texture. In relation to the postemergence herbicides, atrazine, diuron, prometryn, flumioxazin, fomesafen, lactofen, saflufenacil, amonio-glufosinate and glyphosate can be used aiming the chemical control of C.spectabilis. Herbicides chlorimuron-ethyl, diclosulan, imazethapyr, pyrithiobac-sodium, trifloxysulfuron-sodium, clomazone, pendimethalin, S-metolachlor and trifluralin applied in preemergence, and imazethapyr, pyrithiobac-sodium, flumiclorac, bentazon and clethodim applied in postemergence caused low levels of injury to C.spectabilis plants, making necessary the development of new searches to ensure the selectivity of these products.

Changes in Photosynthesis and Oxidative Stress in Wheat Plants Submmited to Herbicides Application

The use of herbicides, even in tolerant crops, can cause stress evidenced by increase phytotoxicity affecting growth and development. The objectives of this study were to evaluate herbicides effect from different mechanisms of action in photosynthetic and oxidative stress parameters, as well visual phytotoxicity and wild radish control in wheat crop, cultivar Quartzo. Two trials were conducted where the first one evaluated the photosynthetic parameters on wheat plants in two seasons collection, following the application of herbicides bentazon, clodinafop, iodosulfuron, metribuzin, metsulfuron and 2,4-D; and the second one evaluated wild radish (Raphanus sativus) control, wheat phytotoxicity and yield due to bentazon, iodosulfuron, metribuzin, metsulfuron and 2,4-D herbicides application. Photosynthetic rate, stomatal conductance and transpiration were negatively affected by metribuzin, metsulfuron and 2,4-D herbicides at 24 and 120 HAS (hours after spraying) compared to control. Oxidative stress was similar or lower to control, when herbicide was applied and, in general, there was no difference between application times. Lipid peroxidation, catalase activity and phenols were higher in the first collection time. The application of herbicides iodosulfuron and 2,4-D reduces chlorophylls and carotenoids in wheat. Herbicides bentazon, iodosulfuron, metribuzin, metsulfuron and 2,4-D are selective to wheat, cultivar Quartzo and do not affect wheat yield. 2,4-D, metribuzin and iodosulfuron are more efficient for wild radish control.

Induction of apoptosis in cancer cells by tumor necrosis factor and butyrolactone, an inhibitor of cyclin-dependent kinases

Induction of apoptosis by tumor necrosis factor (TNF) is modulated by changes in the expression and activity of several cell cycle regulatory proteins. We examined the effects of TNF (1-100 ng/ml) and butyrolactone I (100 µM), a specific inhibitor of cyclin-dependent kinases (CDK) with high selectivity for CDK-1 and CDK-2, on three different cancer cell lines: WEHI, L929 and HeLa S3. Both compounds blocked cell growth, but only TNF induced the common events of apoptosis, i.e., chromatin condensation and ladder pattern of DNA fragmentation in these cell lines. The TNF-induced apoptosis events were increased in the presence of butyrolactone. In vitro phosphorylation assays for exogenous histone H1 and endogenous retinoblastoma protein (pRb) in the total cell lysates showed that treatment with both TNF and butyrolactone inhibited the histone H1 kinase (WEHI, L929 and HeLa) and pRb kinase (WEHI) activities of CDKs, as compared with the controls. The role of proteases in the TNF and butyrolactone-induced apoptosis was evaluated by comparing the number and expression of polypeptides in the cell lysates by gel electrophoresis. TNF and butyrolactone treatment caused the disappearance of several cellular protein bands in the region between 40-200 kDa, and the 110- 90- and 50-kDa proteins were identified as the major substrates, whose degradation was remarkably increased by the treatments. Interestingly, the loss of several cellular protein bands was associated with the marked accumulation of two proteins apparently of 60 and 70 kDa, which may be cleavage products of one or more proteins. These findings link the decrease of cyclin-dependent kinase activities to the increase of protease activities within the growth arrest and apoptosis pathways induced by TNF.

Measurement of intestinal permeability using mannitol and lactulose in children with diarrheal diseases

The excretion ratio of lactulose/mannitol in urine has been used to assess the extension of malabsorption and impairment of intestinal permeability. The recovery of lactulose and mannitol in urine was employed to evaluate intestinal permeability in children with and without diarrhea. Lactulose and mannitol probes were measured using high-performance liquid chromatography with pulsed amperometric detection (HPLC-PAD). Two groups of solutions containing 60 µM sugars were prepared. Group I consisted of glucosamine, mannitol, melibiose and lactulose, and group II of inositol, sorbitol, glucose and lactose. In the study of intra-experiment variation, a sample of 50 µl from each group was submitted to 4 successive determinations. The recovered amounts and retention times of each sugar showed a variation <2 and 1%, respectively. The estimated recovery was >97%. In the study of inter-experiment variation, we prepared 4 independent samples from groups I and II at the following concentrations: 1.0, 0.3, 0.1, 0.03 and 0.01 mM. The amounts of the sugars recovered varied by <10%, whereas the retention times showed an average variation <1%. The linear correlation coefficients were >99%. Retention (k'), selectivity (a) and efficiency (N) were used to assess the chromatographic conditions. All three parameters were in the normal range. Children with diarrhea presented a greater lactulose/mannitol ratio compared to children without diarrhea.

The molecular basis of selective permeability of connexins is complex and includes both size and charge

Although gap junction channels are still widely viewed as large, non-specific pores connecting cells, the diversity in the connexin family has led more attention to be focused on their permeability characteristics. We summarize here the current status of these investigations, both published and on-going, that reveal both charge and size selectivity between gap junction channels composed of different connexins. In particular, this review will focus on quantitative approaches that monitor the expression level of the connexins, so that it is clear that differences that are seen can be attributed to channel properties. The degree of selectivity that is observed is modest compared to other channels, but is likely to be significant for biological molecules that are labile within the cell. Of particular relevance to the in vivo function of gap junctions, recent studies are summarized that demonstrate that the connexin phenotype can control the nature of the endogenous traffic between cells, with consequent effects on biological effects of gap junctions such as tumor suppression.

The effect of porphyrins on normal and transformed mouse cell lines in the presence of visible light

Photodynamic therapy consists of the uptake of a photosensitizing dye, often a porphyrin, by tumor tissue and subsequent irradiation of the tumor with visible light of an appropriate wavelength matched to the absorption spectrum of the photosensitizing dye. This class of molecules produces reactive oxygen species when activated by light, resulting in a direct or indirect cytotoxic effect on the target cells. Photodynamic therapy has been used in the treatment of cancer but the technology has a potential for the treatment of several disease conditions mainly because of its selectivity. However, it is not clear why the porphyrins are retained preferentially by abnormal tissue. This paper describes a study of the effect of the association of porphyrin and visible light on two mouse fibroblast cell lines: A31, normal cells and B61, an EJ-ras transformed variant of A31. Two water-soluble porphyrins were used, a positively charged one, tetra(N-methyl-4-pyridyl)porphyrin chloride, and a negatively charged one, tetra(4-sulfonatophenyl)porphyrin-Na salt (TPPS4) in order to assess the effect on cell survival. The results suggest that the B61 cell line is more sensitive to incubation with the anionic porphyrin (TPPS4) followed by light irradiation and that the anionic porphyrin is more efficient in killing the cells than the cationic porphyrin.