Phytotoxicity Of Herbicides Research Articles

Effects of Chiral 3-Dichloroacetyl Oxazolidine on Glutathione S-Transferase and Antioxidant Enzymes Activity in Maize Treated with Acetochlor

The objective of this paper was to investigate the protective effect of three potential herbicide safeners (3-dichloroacetyl oxazolidine and its two optical isomers) on detoxifying to chloroacetanilide herbicide acetochlor in maize. In this study, physiological and biochemical tests were conducted under laboratory condition in 2015. All safeners increased the expression levels of herbicide detoxifying enzymes, including glutathione S-transferases (GST), catalase (CAT) and peroxidase (POD) to reduce chloroacetanilide herbicide phytotoxicity in maize seedlings. Our results suggest that the R-isomer of R-29148 can induce glutathione (GSH) expression, GST activity, and affinity for the 1-chloro2,4-dinitrobenzene (CDNB) substrate in maize, which can protect maize from injury by chloroacetanilide herbicide acetochlor. Further information on the chiral safener role in antioxida

Phytotoxicity of Herbicides in Seedlings of Sweet Passion Fruit

The culture of sweet passion fruit has been increasingly studied and exploited commercially in Brazil, with emphasis on the State of São Paulo. This is due to the high value achieved in the market of fresh fruit and be considered a food with functional properties beneficial to human health. However, the cultivation on a large scale finds some obstacles, as the control of weeds with the use of herbicides. In this sense, the objective of this work was to evaluate the phytotoxicity of seven herbicides with different mechanisms of action in seedlings of sweet passion fruit. Different variables were assessed: initial plant height (IPH) and final plant height (FPH); initial number of sheets (INS) and end number of sheets (ENS); intoxication of plants (INTO); fresh leaf mass (FLM) and dry leaf mass (DLM); fresh stem mass (FSM); dry steam mass (DSM); fresh root mass (FRM) and dry root mass (DRM) and total dry mass (TDM). Chlorimuron-ethyl (ALS inhibitor), glyphosate (EPSP synthase inhibitor), paraquat (photosystem I inhibitor) and atrazine (photosystem II inhibitor) have the higher effect on the variables analyzed, and they caused some kind of intoxication in the plants of sweet passion fruit. Conversely, haloxyfop-p-methyl (ACCase inhibitor) and fomesafen (protox inhibitor) showed a lesser effect on the sweet passion fruit plants.

Manejo de plantas daninhas em milho RR® com herbicidas aplicados isoladamente ou associados ao glyphosate

The objective of this work was to evaluate the effectiveness, selectivity and effect on yield components of RR® maize as a function of herbicide application, applied alone or in a tank mix. The experiment was conducted in a randomized block design, with four replications, and treatments were control without weeding, control with weeding, glyphosate, glyphosate + [atrazine+simazine], glyphosate + [atrazine + simazine], glyphosate + tembotrione, glyphosate+mesotrione, T8-glyphosate + nicosulfuron, glyphosate + 2,4-D, glyphosate + [atrazine + S-metolachlor], T11-glyphosate + (atrazine + S-metolachlor), glyphosate + S-metolachlor, glufosinate ammonium, [nicosulfuron + mesotrione], glyphosate + [nicosulfuron + mesotrione] and glyphosate + [nicosulfuron+mesotrione] + [atrazine + simazine]. Herbicide phytotoxicity to a SYN Supremo VIP3 maize hybrid and control of Urochloa plantaginea and Digitaria ciliaris were evaluated at 7, 14, 21 and 28 days after treatment application. Prior to crop harvest, we determined weed control and, in ten plants per experimental unit, the variables related to grain yield components such as ear insertion height, ear length, number of rows and grains per rows on the ears of corn. During harvest, the mass of one thousand grains and yield were evaluated. It was observed that all herbicide treatments caused low phytotoxicity in maize, except for the post-emergence tank mix composed of glyphosate + 2,4-D and glyphosate + mesotrione, that showed the highest injuries in the four evaluated periods. Most of the herbicides showed good control of D. ciliaris and U. plantaginea, except for the pre-harvest mixture of glyphosate + 2,4-D. The post-emergence glyphosate + [atrazine + simazine] tank mix demonstrated the highest grain yield. It can be concluded, therefore, that depending on the association of herbicides, synergistic effect occurs for both weed control and crop phytotoxicity, being productivity being the main influenced variable.

Weed Management in Beans Using Subdoses of Fluazifop-P-Butyl + Fomesafen

ABSTRACT: The objective of this work was to evaluate the effect of reduced doses of the commercial mixture composed of fluazifop-p-butil + fomesafen, applied for the management of common weeds in beans. The experiment was conducted in a completely randomized block design, with a 5x2+1 factorial arrangement and with four replications. In factor A, there were five percentual doses (100, 87.5, 75.0, 62.5 and 0.0%), in relation to the recommended commercial dose (2 L ha-1) of fluazifop-p-butil + fomesafen, which corresponded to 2.00; 1.75; 1.50; 1.25 and 0.00 L ha-1. Factor B was composed by two development stages of black beans (three and eight trefoils) and weeds: black-jack (two to four and four to eight leaves) and southern crabgrass (two leaves to one tiller and one to four tillers) with one weeded control treatment. The variables evaluated for the control of black-jack and southern crabgrass were: herbicide phytotoxicity to the crop, number of pods per plant, number of grains per pod, 1,000 grain weight and grain yield of the crop. The results demonstrated that the use of fluazifop-p-butil + fomesafen, at all evaluated doses evaluated and application periods, caused low phytotoxicity to the crop, less than 12%. The use of reduced doses of this herbicide presents efficient control of black-jack and southern crabgrass, mainly at the initial development stages of these weed species. The economic threshold dosage of fluazifop-p-butil + fomesafen to control these weeds was 1.23 L ha-1.

The expression of detoxification genes in two maize cultivars by interaction of isoxadifen-ethyl and nicosulfuron

Herbicide safeners protect crop plants from herbicide phytotoxicity, but an understanding of their molecular mechanisms is still lacking. We investigated the effects of the safener isoxadifen-ethyl and/or nicosulfuron on the expression of 10 genes, 8 glutathione transferases (GSTs), 1 glutathione transporter and 1 multidrug resistance protein gene in two maize cultivars. Nicosulfuron and isoxadifen-ethyl induce different detoxification enzyme genes. The expression analyses of the 10 genes revealed that most were expressed much higher in ‘Zhengdan958’ than those in ‘Zhenghuangnuo No.2’, both in control and in isoxadifen-ethyl- and/or nicosulfuron-treated plants. The expression levels of ZmGSTIV, ZmGST6, ZmGST31 and ZmMRP1 in two maize cultivars were up-regulated by isoxadifen-ethyl only, or in combination with nicosulfuron, whereas nicosulfuron down-regulated the expression of eight genes. Thus, ZmGSTIV, ZmGST6, ZmGST31 and ZmMRP1 could be considered safener-responsive and may be the core genes responsible for isoxadifen-ethyl increasing the tolerance of maize to nicosulfuron.

ВЛИЯНИЕ ИНТЕРМЕДИАТОВ ЦИКЛА КРЕБСА НА РОСТ И РАЗВИТИЕ КУЛЬТУРЫ СИНЕГНОЙНОЙ ПАЛОЧКИ

This paper investigates the effect of organic acids - Krebs cycle intermediates (citric, α-Ketoglutaric, succinic, malic and oxalic acids) - taken in concentrations from 10 -9 to 10 -15 M on the growth of pure Pseudomonas aeruginosa, its developmental stages, heredity and multiplication. It is established that ultra-small concentrations of the Krebs cycle intermediates do stimulate the growth of P. aeruginosa. Nanopreparations based on the Krebs cycle acids with their concentrations ranging from 10 -9 to 10 -12 M are shown to exhibit the highest growth-stimulating action. In an experiment aimed at investigating a joint action of Krebs cycle intermediate nanopreparations and herbicides, a synergistic effect of increased herbicide phytotoxicity was revealed. The propensity of the P. aeruginosa strain to accelerated reproduction under the influence of a stimulating agent is not preserved in its third generation. It is determined that the stimulation of P. aeruginosa growth has limit values for each concentration and is of a cyclical character. A nanopreparation with a concentration of 10 -11 M is shown to exhibit the highest stimulating action.

Studies on Phytotoxicity of Herbicides and Herbicide Mixtures and its effect on Yield of Direct-Sown Rice (Oryza sativa L.)

Studies on Phytotoxicity of Herbicides and Herbicide Mixtures and its effect on Yield of Direct-Sown Rice (Oryza sativa L.)

Enantioselective Phytotoxicity of Dichlorprop to Arabidopsis thaliana: The Effect of Cytochrome P450 Enzymes and the Role of Fe.

The ecotoxicology effects of chiral herbicides have long been recognized and have drawn increasing attention. The toxic mechanisms of herbicides in plants are involved in production of reactive oxygen species (ROS) and cause damage to target enzymes, but the relationship between these two factors in the enantioselectivity of chiral herbicides has rarely been investigated. Furthermore, even though cytochromes P450 enzymes (CYP450s) have been related to the phytotoxicity of herbicides, their roles in the enantioselectivity of chiral herbicides have yet to be explored. To solve this puzzle, the CYP450s suicide inhibitor 1-aminobenzotriazole (ABT) was added to an exposure system made from dichlorprop (DCPP) enantiomers in the model plant Arabidopsis thaliana. The results indicated that different phytotoxicities of DCPP enantiomers by causing oxidative stress and acetyl-CoA carboxylase (ACCase) damage were observed in the presence and the absence of ABT. The addition of ABT decreased the toxicity of (R)-DCPP but was not significantly affected that of (S)-DCPP, resulting in smaller differences between enantiomers. Furthermore, profound differences were also observed in Fe uptake and distribution, exhibiting different distribution patterns in A. thaliana leaves exposed to DCPP and ABT, which helped bridge the relationship between ROS production and target enzyme ACCase damage through the function of CYP450s. These results offer an opportunity for a more-comprehensive understanding of chiral herbicide action mechanism and provide basic evidence for risk assessments of chiral herbicides in the environment.

Isoxadifen-Ethyl Derivatives Protect Rice from Fenoxaprop-P-Ethyl–associated Injury during the Control of Weedy Rice

Fenoxaprop-P-ethyl, a phenoxy herbicide of the aryloxy–phenoxy–propionic acid group, had a strong control effect when applied POST to weedy rice in this study, with the effective concentrations of 294 μM and 218 μM of herbicide causing 50% inhibition (IC50) in plant height and fresh weight values, respectively. However, fenoxaprop-P-ethyl caused phytotoxicity in cultivated rice. Isoxadifen-ethyl, a widely used herbicide safener in rice, can decrease the phytotoxicity caused by fenoxaprop-P-ethyl. Owing to the extremely similar morphological features and physiological properties of weedy and cultivated rice, it is not practical to spray isoxadifen-ethyl directly on cultivated rice plants to safen them. Applying the safener directly to cultivated rice seeds may be a practical alternative method. To improve the biological activity of isoxadifen-ethyl seed treatments, novel compounds were designed by splicing other groups, including amines, amino acids, and 2- methoxy-5-nitrophenol sodium salt, to the parental structure of isoxadifen-ethyl. Through hydrolysis, acyl chlorination, acyl amination, and esterification, a series of isoxadifen-ethyl derivatives were synthesized and their structures were determined by mass spectrometry and1H nuclear magnetic resonance spectroscopy. The biological activities of five of the isoxadifen-ethyl derivatives, which possessed recovery effects similar to isoxadifen-ethyl, were able to relieve herbicide phytotoxicity. In pot experiments, isoxadifen-ethyl showed almost no activity as a seed treatment, while three derivative compounds, when used independently as seed treatments, were able to prevent the damage caused by fenoxaprop-P-ethyl. The results will help to develop a new control method for weedy rice, thereby decreasing production costs and increasing farmers’ incomes.

Management of Adenocalymna impressum on pasture in the northwestern Mato Grosso

The occurrence of weeds in pastures is a factor that represents a loss of productivity because they compete directly with the essential elements and space with the forage. We aimed with this study was to evaluate the chemical control of Adenocalymna impressum with experiments conducted in the municipality of Juruena, Mato Grosso. Control techniques evaluated were: fluroxypyr + aminopyralid in adult plant; (fluroxypyr + aminopyralid) + (triclopyr) in adult plant; fluroxypyr + aminopyralid on regrowth; (fluroxypyr + aminopyralid) + (triclopyr)on regrowth; (picloram + triclopyr) basal; (picloram + triclopyr) on stump (after mowing). The experiment was conducted in a randomized block design with four replications. We give phytotoxicity notes from 0 to 100, where 100 means death of the plant, we also evaluated phytotoxicity of foliar herbicides on Brachiaria brizantha cv. ‘Marandu’. The evaluations were performed at 10, 20, 30, 60, 90, 120 and 150 days after application. The data were submitted to analysis of variance and means were compared by Tukey`s test at 5% probability, using the SISVAR program. All treatments showed weed control, but only the herbicide picloram + triclopyreffectively controlled A. Impressum. Damage of foliar herbicides on B. brizantha was temporary, it recovered on 3rd assessment.

Utilization of Chlorophyll Fluorescence Imaging Technology to Detect Plant Injury by Herbicides in Sugar Beet and Soybean

Sensor technologies are expedient tools for precision agriculture, aiming for yield protection while reducing operating costs. A portable sensor based on chlorophyll fluorescence imaging was used in greenhouse experiments to investigate the response of sugar beet and soybean cultivars to the application of herbicides. The sensor measured the maximum quantum efficacy yield in photosystem II (PS-II) (Fv/Fm). In sugar beet, the averageFv/Fmof 9 different cultivars 1 d after treatment of desmedipham plus phenmedipham plus ethofumesate plus lenacil was reduced by 56% compared to the nontreated control. In soybean, the application of metribuzin plus clomazone reducedFv/Fmby 35% 9 d after application in 7 different cultivars. Sugar beets recovered within few days from herbicide stress while maximum quantum efficacy yield in PS-II of soybean cultivars was reduced up to 28 d. At the end of the experiment, approximately 30 d after treatment, biomass was reduced up to 77% in sugar beet and 92% in soybean. Chlorophyll fluorescence imaging is a useful diagnostic tool to quantify phytotoxicity of herbicides on crop cultivars directly after herbicide application, but does not correlate with biomass reduction.

Rapid Biodegradation of the Herbicide 2,4-Dichlorophenoxyacetic Acid by Cupriavidus gilardii T-1.

Phytotoxicity and environmental pollution of residual herbicides have caused much public concern during the past several decades. An indigenous bacterial strain capable of degrading 2,4-dichlorophenoxyacetic acid (2,4-D), designated T-1, was isolated from soybean field soil and identified as Cupriavidus gilardii. Strain T-1 degraded 2,4-D 3.39 times more rapidly than the model strain Cupriavidus necator JMP134. T-1 could also efficiently degrade 2-methyl-4-chlorophenoxyacetic acid (MCPA), MCPA isooctyl ester, and 2-(2,4-dichlorophenoxy)propionic acid (2,4-DP). Suitable conditions for 2,4-D degradation were pH 7.0-9.0, 37-42 °C, and 4.0 mL of inoculums. Degradation of 2,4-D was concentration-dependent. 2,4-D was degraded to 2,4-dichlorophenol (2,4-DCP) by cleavage of the ether bond and then to 3,5-dichlorocatechol (3,5-DCC) via hydroxylation, followed by ortho-cleavage to cis-2-dichlorodiene lactone (CDL). The metabolites 2,4-DCP or 3,5-DCC at 10 mg L-1 were completely degraded within 16 h. Fast degradation of 2,4-D and its analogues highlights the potential for use of C.gilardii T-1 in bioremediation of phenoxyalkanoic acid herbicides.

Biochar Soil Additions Affect Herbicide Fate: Importance of Application Timing and Feedstock Species.

Biochar (BC), solid biomass subjected to pyrolysis, can alter the fate of pesticides in soil. We investigated the effect of soil amendment with several biochars on the efficacy of two herbicides, clomazone (CMZ) and bispyribac sodium (BYP). To this aim, we evaluated CMZ and BYP sorption, persistence, and leaching in biochar-amended soil. Sorption of CMZ and BYP was greater in soil amended with BC produced at high temperature (700 °C). Significant sorption of the neutral CMZ herbicide also occurred in amended soil with BC prepared at low temperature (350 and 500 °C). For both herbicides, desorption possessed higher hysteretic behavior in soil amended with BC made at 700 °C (pyrolysis temperature). Dissipation of CMZ was enhanced after addition of BCs to soil, but no correlation between persistence and sorption was observed. Persistence of BYP was up to 3 times greater when BC made at 700 °C was added to soil. All BCs suppressed the leaching of CMZ and BYP as compared to the unamended soil. Amendment with 700 °C BC inhibited the action of CMZ against weeds, but 350 and 500 °C BCs had no such effect when added to soil. BYP activity was similar to that exhibited by unamended soil after the addition of 700 °C BC. From these results, biochar amendments can be a successful strategy to reduce the environmental impact of CMZ and BYP in soil. However, the phytotoxicity of soil-applied herbicides will depend on BC sorption characteristics and the pesticide's chemical properties, as well as the pesticide application timing (e.g., pre- or postemergence). According to our results, proper biochar screening with intended pesticides in light of the application mode (pre- or postemergence) is required prior to use to ensure adequate efficacy.

Role of reactive oxygen species in auxin herbicide phytotoxicity: current information and hormonal implications — are gibberellins, cytokinins, and polyamines involved?

It has been suggested that reactive oxygen species (ROS) participate in the injury and death of sensitive plants treated with auxin herbicides. However, their precise role in the phytotoxicity of these compounds has not been completely elucidated. ROS might not only be essential for inducing epinasty, senescence, and tumours, but they might be crucial to the generation of ethylene, abscisic acid, and jasmonic acid, which are known to be triggered upon application of these compounds. Also, the main sources of ROS overproduction and their subcellular location in plants treated with auxin herbicides have not yet been clarified. Recent studies have suggested a role for xanthine oxidase (XOD) (which produces superoxide radical ([Formula: see text]) and has activity related to nucleic acid catabolism) and for peroxisomes in the oxidative stress and senescence induced by auxin herbicides in the leaves of sensitive plants. However, confirmatory studies at the molecular level are still needed, as well as studies on the possible involvement of other hormones, such as gibberellins, cytokinins, and polyamines, and their corresponding crosstalk with ROS, in the mode of action of auxin herbicides. The results from these studies could not only help to clarify the mechanism of phytotoxicity of these compounds, but also to enable the design of ecologically safer herbicides for agriculture.

Creation of starting material of high oleic sunflower resistant to sulfonylurea herbicides

The results of studies for the period of 2012-2015 on creation of high oleic starting material resistant to granular herbicide Express 75 from a working collection of parent forms of the Plant Production Institute nd. a VYa Yuryev NAAS are presented. The work was done by crossing parent forms, basing on combinations of positive features, namely sulfonylurea herbicide resistance gene and high oleic acid content.The aim and tasks of the study. The purpose was to determine oleic and linoleic acid contents in different sunflower forms, to select biotypes with high oleic acid content and resistant to sulfonylurea herbicide, to create starting material for sunflower breeding for resistance to sulfonylurea herbicide and high oleic acid content.Material and methods. The study material was fertile lines Kh 526 V and Kh 201 V from the working collection of the Laboratory of Sunflower Breeding and Genetics of the Plant Production Institute nd. a VYa Yuryev. Inbred lines and hybrids with high content of oleic acid triglycerides were created by conventional methods: analytical and heterosis sunflower breeding. Oil was prepared according to the modified Peisker method, and fatty acid composition of oil was analyzed by gas chromatography. The field experiments were carried out in accordance with the methodology for statistical processing of pesticide trial data. Herbicide phytotoxicity for sunflower plants was assessed by affection degree, using a rating scale.Results and discussion. Plants were treated in the phase of 4-6 true leaves with post-emergence granular herbicide Express75 in 2012-2015. A three-liter hand sprayer was used. The dose was 25 g/ha, and the fluid consumption was300 L / ha. Surviving plants were inbred. In addition, female form Kh 526 V and male form Kh 201 V were crossed on fertile basis with following individual election of plants.Accessions selected with the rating scale, according to the world literature, are supposed to have the resistance gene. Chromatography revealed several accessions with high content of oleic acid. Hereditary nature of high content of oleic acid triglycerides was experimentally confirmed and does not admit of doubt, trait is controlled by one partially dominant gene, or it is considered as fully dominant. Sunflower should have more than 82% of oleic acid omega-9 inoil (monounsaturated fatty acids) and low content of linoleic acid omega-6.Conclusions. Over the study period, a possibility of combining high oleate content in sunflower oil with resistance to sulfonylurea herbicide, namely to granular Express 75 applied at the dose of25 g / ha, was experimentally confirmed.The best way to create inbred lines with oleic oil in combination with herbicide resistance is hybridization of induced high oleic forms on fertile basis followed by inbreeding, backcrossing and individual selection of plants for a set of agricultural valuable traits.Thus, the creation of starting material to resistant to sulfonylurea herbicides with high oleic acid content offers a significant advantage in sunflower cultivation, providing access to nutrients from soil for plants, and linoleate content opens new possibilities in industrial and food sectors

Factors Affecting Egyptian Broomrape (Orobanche aegyptiaca) Control in Carrot

Carrot is a high-value cash crop that is grown in Israel throughout the year. Egyptian broomrape is a chlorophyll-lacking, obligate, root holoparasite that parasitizes members of many botanical families, including the Apiaceae. At high infestation levels, Egyptian broomrape can cause total yield loss in carrot. A protocol has been developed for the control of Egyptian broomrape in carrot. Because carrots are grown in Israel under fall, winter, and spring conditions, information about the relations between the efficacy of control and temperature is important. Therefore, the objective of this study was to investigate the response of carrot and Egyptian broomrape to herbicides at different phenological stages under varying temperature regimes. This study was conducted under temperature-controlled conditions in a multiclimate greenhouse and in a net house. Applications of the imidazolinone herbicides imazapic and imazamox (each applied at 4.8 g ai ha−1) injured carrot plants and reduced yield and yield quality. Glyphosate effectively controlled Egyptian broomrape and did not negatively affect the carrot plants when applied three times at ≤ 108 g ae ha−1. High temperatures increased the carrot plants’ sensitivity to glyphosate. This study found that three applications of glyphosate at 108 g ae ha−1can prevent Egyptian broomrape damage without causing any damage to the carrot crop. Our results indicate that weather conditions can affect herbicide phytotoxicity in carrot. The highest temperature at the time of herbicide application corresponded to the strongest observed phytotoxic effect. To summarize, effective Egyptian broomrape control can be achieved by three sequential foliar applications of glyphosate (108 g ae ha−1), beginning during the early parasitism stage (i.e., small tubercles). Moreover, applying glyphosate on carrot at high temperature (i.e., 28/22 C day/night temperatures) can injure carrot plants and reduce control efficacy.

Study of bio-efficacy and Phytotoxicity of New Generation Herbicides on Triafamone and Ethoxysulfuron in Direct Seeded Rice (Oryza sativa)

The herbicides triafamone + ethoxysulfuron at (200g/ml/ha and 225 g/ml/ha) and triafamone (225 g/ml/ha) applied at 15 days after planting recorded the zero weed counts of individual species viz., grasses, sedges and broad leaf weeds, weed dry matter production and weed control index favoring to higher grain yield of (5.2 and 5.34 t/ha). Triafamone + ethoxysulfuron (175 g/ml/ha) recorded the least weed count, weed dry matter and cent percent weed control index recorded at 42 days after application (DAA). Ethoxysulfuron (150g/ml/ha) was next in order. No phytotoxicity symptoms was observed in the treatments including double the recommended dose of triafamone + ethoxysulfuron (450 g/ml/ha and 225 g/ml/ha) in respect of leaf chlorosis, tip burning, necrosis, epinasty, hyponasty, vein clearing, wilting and rosetting.

Stomatal behaviors reflect enantioselective phytotoxicity of chiral herbicide dichlorprop in Arabidopsis thaliana

Stomata in plants play vital roles in water transpiration and gas exchange necessary for photosynthesis, which are critical for the plants growth. Until now, however, the effect of chiral herbicides on the response of stomata was poorly understood. To unveil this puzzle, the enantioselective effect of chiral herbicide dichloroprop (DCPP) on stomata in Arabidopsis thaliana was investigated. It was found that (R)-DCPP preferentially promoted the extent of stomatal opening in Arabidopsis leaves, resulting in 59.84% enhancement at 0.3μmol·L−1 comparing to the control, where (S)- and (Rac)-DCPP exhibited no significant differences. Enantioselectivity was also observed in the response of stomata to DCPP. To better understand the mechanism involved, the reactive oxygen species (ROS) production and antioxidant system defense were measured. Interestingly, the ROS production in Arabidopsis leaves was also enantioselective. The (R)-DCPP treatments resulted in 6.08-fold enhancement compared with the control, whereas 1.35- and 2.51-fold increases occurred in (S)-DCPP and (Rac)-DCPP treatments, respectively. The promoting of stomatal opening was positively correlated with ROS production. In addition, the antioxidant system response provided evidence of oxidative stress and damage caused by DCPP. This study confirmed that the ROS produced by DCPP promoted stomatal opening and suggested a potential sight to elucidate the phytotoxicity of chiral herbicides.

Effect of pre-emergence herbicides and timing of soil saturation on the control of six major rice weeds and their phytotoxic effects on rice seedlings

The study evaluated the effects of pre-emergence herbicides and their rates [oxadiazon (0.5 and 1 kg ai ha−1), pendimethalin (1 and 2 kg ai ha−1), and pretilachlor with safener (0.6 kg ai ha−1)], and time of soil saturation establishment after herbicide application [1, 3, 5, and 7 days after spray (DAS)] in controlling the six major rice weeds, and their phytotoxic effects on rice seedling growth. All herbicides provided 100% control of Echinochloa colona, Echinochloa crus-galli, Leptochloa chinensis, Cyperus iria, and Amaranthus spinosus. Murdannia nudiflora was 100% controlled by oxadiazon and pretilachlor with safener, but poorly controlled (22–75%) by pendimethalin. Pendimethalin at 2 kg ai ha−1 was more effective than at 1 kg ai ha−1 in reducing the biomass of the stem, leaf, and root of M. nudiflora irrespective of timing of soil saturation. Rice plant height was reduced to a maximum (77–96%) by pendimethalin at 2.0 kg ai ha−1 followed by oxadiazon at 1.0 kg ai ha−1 (38–70%) compared to the non-treated control. In contrast, the tallest rice plants were observed in the non-treated control and those treated with pretilachlor with safener which had 80–100% rice plant survival. The lowest rice plant survival of 0, 6, 7, and 16% was found in the soil applied with pendimethalin at 2 kg ai ha−1 and saturated at 1, 3, 5, and 7 DAS, respectively, which was followed by oxadiazon at 1 kg ai ha−1. All herbicides except pretilachlor with safener reduced SPAD values with early soil saturation, which improved with delay in soil saturation timing. Pendimethalin at 2 kg ai ha−1 reduced the SPAD values of rice plants by 100–164% relative to the non-treated control and produced the highest phytotoxicity symptoms. Pendimethalin also reduced rice shoot biomass more than oxadiazon, which was compounded by early soil saturation after herbicide application. Pretilachlor with safener was the only herbicide that exhibited low phytotoxic symptoms on rice plants and did not reduce leaf, stem, root, and shoot biomass of rice. Percent reduction in rice leaf, stem, root, and shoot biomass by the different herbicides was in the order of pendimethalin 2 > oxadiazon 1 > pendimethalin 1 > oxadiazon 0.5 > pretilachlor with safener 0.6 kg ai ha−1. Each herbicide treatment reduced rice growth parameters as soil saturation was delayed in the order of 1 DAS > 3 DAS > 5 DAS > 7 DAS. The study suggests that soil water content and herbicide rates are important factors in influencing herbicide phytotoxicity in rice. The application of herbicides should be avoided when the soil is too wet, and irrigation should be delayed at least one week after herbicide application.

Phytotoxicity of chiral herbicide bromacil: Enantioselectivity of photosynthesis in Arabidopsis thaliana

With the wide application of chiral herbicides and the frequent detection of photosystem II (PSII) herbicides, it is of great importance to assess the direct effects of PSII herbicides on photosynthesis in an enantiomeric level. In the present study, the enantioselective phytotoxicity of bromacil (BRO), typical photosynthesis inhibition herbicide, on Arabidopsis thaliana was investigated. The results showed that S-BRO exhibited a greater inhibition of electron transmission in photosystem I (PSI) of A. thaliana than R-BRO by inhibiting the transcription of fnr 1. S-BRO also changed the chlorophyll fluorescence parameters Y (II), Y (NO), and Y (NPQ) to a greater extent than R-Bro. Transcription of genes psbO2, Lhcb3 and Lhcb6 was down-regulated in an enantioselective rhythm and S-BRO caused more serious influence, indicating that S-BRO did worse damage to the photosystem II (PSII) of A. thaliana than R-BRO. This study suggested that S-BRO disturbed the photosynthesis of plants to a larger extent than R-BRO and provided a new sight to evaluate the phytotoxicity of chiral herbicides.