Toxic reactivity of wheat (Triticum aestivum) plants to herbicide isoproturon

Morphoanatomical and Physiological Adaptations of Triticum aestivum L. against Allelopathic Extract of Trianthema portulacastrum L. (Horse purslane)

Weed infestation can be harmful to crop growth and cause severe losses in yield by absorbing nutrients and releasing inhibitory secondary metabolites and thus needs to be controlled for food security. The use of synthetic herbicides is one of the most widely applied methods, but its frequent usage is a serious threat to health and the environment and develops resistance in weeds. Allelopathy is an eco-friendly bio-control method, and Trianthema portulacastrum extracts are known to be effective against various weeds in the crop of Triticum aestivum (wheat), but their effect on the main crop (wheat) is still unknown. The pot experiment was carried out, and various concentrations (30, 60, and 100%) of root and shoot extracts of T. portulacastrum and a synthetic herbicide (Metafin Super) along with control (distilled water) were applied to the wheat plants. Various morphological, physiological, and anatomical parameters were recorded under natural conditions. The objective of this study was to explore the allelopathic impact of T. portulacastrum compared to the synthetic herbicide on the growth of wheat. This study displayed that various growth characteristics of wheat were significantly affected at p ≤ 0.05 by root and shoot water extracts of T. portulacastrum but were less inhibitory as compared to the synthetic herbicide. This inhibition of the growth of wheat was coupled with a significant increase in total free amino acids, K ions, CAT (catalase), proline, epidermal and cortical thickness, and abaxial stomatal density. In addition, a reduction in growth parameters was correlated with a decrease in photosynthetic pigments. This study revealed that the use of T. portulacastrum extracts could be safer than synthetic herbicides for wheat plants and would be beneficial to control weeds in a wheat field.

Effects of Fungicides and Nontarget Pesticides on Accumulation of the Mycotoxin Deoxynivlenol in Wheat

Deoxynivalenol (DON) is an important virulence factor of the Fusarium head blight of wheat and threatens the health of humans. The effect of fungicides on DON production after stressing wheat to produce H2O2 and the effect of nontarget pesticides on DON accumulation are largely unknown. Five pesticides were selected to explore the effect of pesticide-induced oxidative stress on DON production in vitro and in vivo. Epoxiconazole and hexaconazole significantly induced an increase in H2O2 in vitro, and H2O2 further stimulated the production of DON and the expression of the Tri5 gene. Imidacloprid, isoproturon, and mesosulfuron-methyl had no direct effect in vitro. All pesticides activated the activities of superoxide dismutase, catalase, and peroxidase in wheat and caused the excessive accumulation of H2O2. However, excessive H2O2 did not stimulate the accumulation of DON. Imidacloprid indirectly stimulated the production of DON in vivo, which may be due to its impact on the secondary metabolism of wheat. In brief, pesticide-induced H2O2 in vitro is an important factor in stimulating DON production, but the stressed physiological H2O2 in wheat is not sufficient to stimulate DON production. The bioaccumulation results indicated that imidacloprid and epoxiconazole increase the risk of DON contamination, especially under field spraying conditions.

Toxicity assessment of metribuzin and its amelioration through plant growth regulators in Vigna radiata (L.) R. Wilczek

The present experiment was conducted to evaluate the metribuzin-induced stress response in Vigna radiata and to explore the ameliorative role of exogenous application of plant growth regulators (PGRs) against metribuzin toxicity by assessing important biochemical and yield parameters. Prior to the field experiment, dose standardization experiments were performed, and EC₅₀ was calculated for metribuzin. On day 21, field grown V. radiata plants were treated with graded concentrations of metribuzin (0-1000 mg [Formula: see text]). Plants treated with 600 mg [Formula: see text] (EC₅₀) and 1000 mg [Formula: see text] (highest dose) of metribuzin were co-treated individually and simultaneously with gibberellic acid-3 (GA), indole-3 acetic acid (IAA), and salicylic acid (SA). After 7 days of treatment, leaf tissues were analyzed for biochemical parameters, whereas those related to yield were recorded during harvest. The result of this study indicated that metribuzin treatment to V. radiata resulted in increase in lipid peroxidation and reduce chlorophyll and carotenoid contents as well as yield parameters. However, metribuzin-treated plants induced proline accumulation and activity of antioxidant enzymes. Exogenous application of GA, IAA, and SA significantly reduced lipid peroxidation and increased contents of photosynthetic pigments, proline, and antioxidant enzymes thereby increasing yield parameters. It was observed that during metribuzin stress, SA exhibited a better ameliorative response out of the three exogenously applied PGRs, while the combined use of all PGRs exhibited much improved ameliorative response on biochemical and yield parameters of plants.

Phytoremediation of isoproturon-contaminated sites by transgenic soybean

The widespread application of isoproturon (IPU) can cause serious pollution to the environment and threaten ecological functions. In this study, the IPU bacterial N-demethylase gene pdmAB was transferred and expressed in the chloroplast of soybean (Glycine max L. 'Zhonghuang13'). The transgenic soybeans exhibited significant tolerance to IPU and demethylated IPU to a less phytotoxic metabolite 3-(4-isopropylphenyl)-1-methylurea (MDIPU) in vivo. The transgenic soybeans removed 98% and 84% IPU from water and soil within 5 and 14 days, respectively, while accumulating less IPU in plant tissues compared with the wild-type (WT). Under IPU stress, transgenic soybeans showed a higher symbiotic nitrogen fixation performance (with higher total nodule biomass and nitrogenase activity) and a more stable rhizosphere bacterial community than the WT. This study developed a transgenic (TS) soybean capable of efficiently removing IPU from its growing environment and recovering a high-symbiotic nitrogen fixation capacity under IPU stress, and provides new insights into the interactions between rhizosphere microorganisms and TS legumes under herbicide stress.

Combined organic coagulants and photocatalytic processes for winery wastewater treatment

Due to the consumers demand for quality wines, washing and disinfection operations are necessary in wine productions, leading to the generation of large volumes of winery wastewater (WW) with a high organic content which has the potential to cause irreversible environmental impacts. The aim and novelty of this work is the production of natural organic coagulants (NOCs) to be applied in coagulation-flocculation-decantation (CFD) process. To complement this treatment process, it is also aimed the performed a photo-Fenton process, combining hydrogen peroxide (H₂O₂) and potassium persulfate (KPS). The Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscope (SEM) showed that NOCs are carbon-based materials with adsorption capacity. Under the best operational conditions, NOCs achieved a turbidity removal between 86.2 and 98.9%, a total suspended solids (TSS) removal ranging between 85.0 and 94.9% and a dissolved organic carbon (DOC) removal ranging between 14.1 and 44.9%. To degrade the DOC present in the WW, different advanced oxidation processes (AOPs) were tested. Results showed that KPS-photo-Fenton, under the best operational conditions [Fe²⁺] = 2.5 mM, [KPS] = 1.0 mM, pH = 3.0, radiation UV-C mercury lamp (254 nm), agitation 350 rpm, temperature 298 K, reaction time 240 min achieved a DOC removal of 91.2 and 96.8%, with a H₂O₂ consumption of 156.9 and 199.0 mM, respectively for red and white WW. With application of combined CFD-KPS-photo-Fenton process, it was observed an increase of DOC removal with lower H₂O₂ consumptions. The energy consumption of the photosystem was evaluated by application of electric energy per mass (E_EM). The application of KPS-photo-Fenton process achieved an E_EM of 0.308 and 0.0309 kWh/g/L DOC, with a cost of 2.05 and 2.59 €/g/L DOC respectively for red and white WW. The combination of CFD-KPS-photo-Fenton decreased significantly the costs of treatment and the treated wastewater achieved the Portuguese legal values for wastewater discharge. This work shows that NOCs are a promising technology that can be an alternative to traditional metal salts, the combination of sulfate radicals with hydroxyl radicals can achieve high DOC removal and the combination of CFD with KPS-photo-Fenton process can decrease the operational costs.

Strengthening leaf physiological functioning and grain yield formation in heat-stressed wheat through potassium application

Wheat crops are highly sensitive to high temperatures during their reproductive and grain-filling phases. We hypothesized that potassium could increase thermotolerance in wheat during grain filling by protecting cellular organelles, particularly chlorophyll, from heat injury. Two wheat genotypes, Ujala-16 (relatively heat tolerant) and Anaj-17 (relatively susceptible) were grown in pots and were submitted to 4 and 8 days of heat stress under polythene sheets 1 week after anthesis. One day before the onset of heat stress, 2% potassium (K) as K₂SO₄ was sprayed on all the plants. Flag leaves from both genotypes were collected after 4 and 8 days of heat stress. Leaf physiology changes were measured to quantify heat damage and to understand the K-induced recovery mechanism. The crop was harvested 125 days after sowing, and grain yield data were collected. Increasing duration of heat stress significantly impaired leaf physiology and grain yield of both studied wheat genotypes. Compared with control (under optimum temperature), 4 and 8 days heat-stressed plants produced 11 and 19% lesser grain yield per spike (averaged across genotypes and in the second years of study), respectively. Likewise, 4- and 8-days heat-stressed plants had 15 and 37% (averaged across genotypes and in the second years of study) lower flag leaf photosynthesis, respectively, compared with control plants. Across the genotypes, 8-days heat caused significantly more grain yield loss in Anaj-17 during the second year than in Ujala-16. Foliar K significantly restored leaf chlorophyll, Pn, Fv/Fm by reducing cellular membrane damage in the heat-stressed plants. This physiological recovery and activation of the plant defensive system by K under high-temperature stress protected the growth and grain development. For example, K_-treated plants produced 19% higher 1,000 grain weight in 8 days of heat stress (across genotypes and in the second years of study) compared with water-treated plants under the hot environment of the respective thermal regime. Our study suggests that wheat performance under terminal heat stress can be improved through the exogenous application of K.

Expression of CYP76C6 Facilitates Isoproturon Metabolism and Detoxification in Rice

Agricultural chemical residues in farmland and crops is one of the serious public issues that constantly threatens crop production, food security, and human health. Understanding their decay mechanism in crops for accelerating their degradative metabolism is important. In this study, a rice uncharacterized cytochrome P450 gene encoding CYP76C6 was functionally identified in rice exposed to isoproturon (IPU). To verify the role of CYP76C6 in rice resistance to IPU toxicity, CYP76C6 overexpression (OEs) and knockout mutant rice by CRISPR/Cas9 were generated through genetic transformation and gene-editing technologies. Assessment of growth and physiological responses revealed that the growth of OE lines was improved, the IPU-induced cellular damage was attenuated, and IPU accumulation was significantly repressed, whereas the Cas9 lines displayed a contrasting phenotype compared to the wild-type. Both relative contents of IPU metabolites and conjugates in OE lines were reduced and those in Cas9 line were increased, suggesting that CYP76C6 plays a critical role in IPU degradation. Our study unveils a new regulator, together with its mechanism for IPU decay in rice crops, which will be used in reality to reduce environmental risks in food safety and human health.

Hyperspectral imaging with shallow convolutional neural networks (SCNN) predicts the early herbicide stress in wheat cultivars

The toxicity impacts of herbicides on crop, animals, and human are big problems global wide. The rapid and non-invasive ways for assessing herbicide-responsible effects on crop growth regarding types and levels still remain unexplored. In this study, visible/near infrared hyperspectral imaging (Vis/NIR HSI) coupled with SCNN was used to reveal the different characteristics in the spectral reflectance of 2 varieties of wheat seedling leaves that were subjected to 4 stress levels of 3 herbicide types during 4 stress durations and make early herbicide stress prediction. The first-order derivative results showed the spectral reflectance exhibited obvious differences at 518-531 nm, 637-675 nm and the red-edge. A SCNN model with attention mechanism (SCNN-ATT) was proposed for herbicide type and level classification of different stress durations. Further, a SCNN-based feature selection model (SCNN-FS) was proposed to screen out the characteristic wavelengths. The proposed methods achieved 96% accuracy of herbicide type classification and around 80% accuracy of stress level classification for both wheat varieties after 48 h. Overall, this study illustrated the potential of using Vis/NIR HSI to rapidly distinguish different herbicide types and serial levels in wheat at an early stage, which held great value for developing on-line herbicide stress recognizing methods in the field.

The Growth, physiological and biochemical response of foxtail millet to atrazine herbicide

Foxtail millet (Pennisetum glaucum L.) is a vital crop that is planted as food and fodder crop around the globe. There is only limited information is present for abiotic stresses on the physiological responses to atrazine. A field experiment was conducted to investigate the effects of different atrazine dosages on the growth, fluorescence and physiological parameters i.e., malonaldehyde (MDA) and reactive oxygen species (ROS) (H₂O₂ and O₂) in the leaves to know the extent of atrazine on oxidative damage of foxtail millet. Our experiment consisted of 0, 2.5, 12.5, 22.5 and 32.5 (mg/kg) of labeled atrazine doses on 2 foxtaill millet varieties. High doses of atrazine significantly enhanced ROS and MDA synthesis in the plant leaves. Enzymes activities like ascorbate peroxidase (APX) and peroxidase (POD) activities enhanced, while catalase (CAD) and superoxide dismutase (SOD) activities reduced with increasing atrazine concentrations. Finally atrazine doses at 32.5 mg/kg reduced chlorophyll contents, while chlorophyll (a/b) ratio also enhanced. Biomass, plant height, chlorophyll fluorescence parameters, minimal and maximal fluorescence (Fo, Fm), maximum and actual quantum yield, photochemical quenching coefficient, and electron transport rate are decreased with increasing atrazine doses.

Residues of Reduced Herbicides Terbuthylazine, Ametryn, and Atrazine and Toxicology to Maize and the Environment through Salicylic Acid

Terbuthylazine (TBA), ametryn (AME), and atrazine (ATZ) are triazine family herbicides. They are dominantly used in the field of cereal crops like wheat and maize for prevention of upland from annual gramineous and broad-leaved weeds, with attributes of weed efficiency broad spectrum and good market performance. Salicylic acid (SA) is a kind of natural plant growth regulator existing widely in the plant kingdom and participating in many physiological and defense processes. In this study, the effects of SA on the detoxification and degradation of herbicides TBA, AME, and ATZ in maize were investigated. When maize plants were exposed to 6 mg kg^-1 of the triazine herbicides, the growth and chlorophyll concentration were reduced, while the membrane permeability increased. After maize was sprayed with 5 mg kg^-1 SA, the herbicide-induced phytotoxicity was significantly assuaged, with the increased content of chlorophyll and decreased cellular damage in plants. Activities of several biomarker enzymes such as SOD, POD, and GST were repressed in the presence of SA. The concentration of the triazine herbicides in maize and the soil determined by high-performance liquid chromatography was drastically reduced by spraying SA. Using LC/Q-TOF-MS/MS, six metabolites and nine conjugates of AME in maize and soil were characterized. The relative contents of AME metabolites and conjugates in maize with SA were higher than those without SA. These results suggest that SA is able to promote the detoxification and decay of these triazine herbicides in maize and soil.

Exogenous addition of silicon alleviates metsulfuron methyl induced stress in wheat seedlings

Uncontrolled application of herbicides in the agricultural field poses a severe risk to crops by affecting their yields. Therefore, methods are required to reduce the toxic effects of herbicides in plants. Studies indicate that silicon (Si) provides tolerance and enhances defence mechanism of the plant against abiotic stress. But its role in alleviating Metsulfuron methyl (Meth) herbicide induced toxicity in wheat seedlings is still not known. This study highlighted the potential of exogenous addition of Si in the alleviation of toxic effect of Meth herbicide in wheat seedlings. The exposure of wheat seedlings to Meth herbicide reduced the growth, photosynthetic pigments, antioxidant enzyme activity and nitric oxide (NO) content. Further, Meth herbicide also increased cell death and decreased cell viability in root tips. However, addition of Si reversed Meth-induced these alterations. Moreover, Si also activates antioxidant system which helps in scavenging of free radicals generated under Meth herbicide stress in wheat seedlings. Application of Si to Meth treated wheat seedlings also up-regulated silicon transporter gene Lsi1 (silicon influx transporter) and some of the antioxidant enzyme genes. All together, the data indicate that Si has capability of alleviating Meth herbicide stress in wheat seedlings but it appears that endogenous NO has a positive role in this endeavour of Si.

Acclimation to cold stress reduces injury from low temperature and bispyribac-sodium on rice

BACKGROUND

In subtropical areas, early planting exposes rice seedlings to cold stress, impairing seedling growth and making them more vulnerable to other stresses including herbicide injury. The objectives of this work were: to evaluate the effect of cold stress on bispyribac-sodium selectivity in rice; to determine the mechanisms of cold tolerance in sensitive ('Epagri 109') and tolerant ('IRGA 424') rice cultivars; and to ascertain that cold acclimatization influences bispyribac-sodium selectivity in rice.

RESULTS

Prolonged cold stress caused high lipid peroxidation, increased rice injury, and stunted growth. Short-term acclimation with cold stress reduced rice injury with bispyribac-sodium. Total phenols were upregulated in rice exposed to cold stress. Prolonged cold stress increased the superoxide dismutase and catalase activity in IRGA 424. Antioxidant activity was higher in the cold-tolerant than in the cold-sensitive cultivar. Only catalase activity was responsive to bispyribac-sodium. OsRAN2, OsGSTL2, and CYP72A21 were upregulated by cold and herbicide stress in both cultivars. OsGSTL2 was upregulated more in IRGA 424 than in Epagri 109. OsFAD8 was upregulated in cold-sensitive rice exposed to short-duration cold stress but was not responsive to bispyribac-sodium.

CONCLUSION

Cold stress reduces bispyribac-sodium selectivity in rice. Short-term acclimation to cold stress reduces the effect of cold stress and enhances bispyribac-sodium selectivity. The tolerance of rice (IRGA 424) to cold stress is due to differential induction of protection genes CYP72A21 and OsGSTL2 associated with herbicide metabolism, together with the accumulation of total phenols and higher activity of antioxidant enzymes.

Biochemical and phytoremediation of Plantago major L. to protect tomato plants from the contamination of cypermethrin pesticide

Phytoremediation is an environmentally friendly therapy to minimize soil pollution. Cypermethrin (CYP) is one of the most frequently used pyrethroid insecticides against a variety of pests. We aimed at evaluating the potential of using an economic plant like tomato (Solanum lycopersicum L.) as a control alone and together with Plantago major L. (PM) for the uptake of CYP residue from contaminated soil, also, investigating the antioxidant enzymes such as (SOD, POD, and CAT) in roots of PM and tomato. For the first time, we studied the intercropping between PM on tomato plants for the uptake of CYP residue from contaminated soil and phytoremediation of PM as a curative plant to save tomato plants from CYP residue. In a pot experiment, we have cultivated PM and tomato in soil polluted with CYP (10 μg g-1). Data showed that PM and tomato accumulated significant amounts of CYP in their tissues. However, PM is better than tomato in uptake CYP from the soil. The longest half-life value (t1/2) of CYP was in PM + tomato together treatment (12.7 days), and the shortest was in the soil with tomato alone (6.81 days). Moreover, the activity of SOD, POD, and CAT in treated tomato and PM roots significantly (p > 0.05) exceeded control plants after 8 days from exposure. In this study, a good strategy was recommended to uptake CYP residue from soil by PM and protect tomato plants from CYP residue as well as safe for human and non-target organisms.

Environmental disappearance of acetochlor and its bioavailability to weed: A general prototype for reduced herbicide application instruction

The consecutive application of herbicide acetochlor has resulted in the widespread drug resistance of weeds and the high risks to environment and human health. To assess environmental behaviors and minimal dosage of acetochlor application in the realistic soil, we systematically investigated the acetochlor adsorption/desorption, mobility, leaching, degradation, weed bioavailability and lethal dosage of acetochlor in three soil types including Nanjing (NJ), Yancheng (YC) and Yingtan (YT). Under the same conditions (60% moisture and darkness), acetochlor had a half-life of disappearance 3 days in NJ, 4.9 days in YC and 25.7 days in YT soils. The HRLC-Q-TOF-MS/MS analyses identified ten metabolites and eight conjugates generated through dealkylation, hydroxylation, thiol conjugation and glycosylation pathways. The acetochlor adsorption to soils ranked in the order of YT > YC > NJ and was committed to the Freundlich model. By examining the effects of soil moisture, microbial activity, illumination/darkness, etc. on acetochlor degradation in soils, we showed that the chemical metabolisms could undergo multiple processes through soil microbial degradation, hydrolysis or photolysis-mediated mechanisms. The longitudinal migration assay revealed that acetochlor leaching ability in the three soils was YT > YC > NJ, which was negatively associated with the order of adsorption behavior. Four kinds of weed were grown in the acetochlor-contaminated NJ soil. The lethal concentrations for the weed plantlets were 0.16-0.3 mg/kg, much lower than the dosage of realistic field application. Overall, our work provided novel insights into the mechanism for acetochlor behaviors in soils, the natural degradation process in the environment, and the lethal concentration to the tested weed plants.

Lead and copper-induced hormetic effect and toxicity mechanisms in lettuce (Lactuca sativa L.) grown in a contaminated soil

Lead (Pb) and copper (Cu) contamination seriously threatens agricultural production and food safety. This study aims to investigate Pb and Cu induced hormetic effect and toxicity mechanisms in lettuce (Lactuca sativa L.) and establish reliable empirical models of potentially toxic elements (PTEs) transfer in the soil-plant system. The content and distribution of Pb and Cu at subcellular levels in lettuce plants were examined using inductively coupled plasma-mass spectrometry, differential centrifugation and micro-X-ray fluorescence spectroscopy. The PTE-loaded capacity of Pb that ensures food safety was lower than that of Cu in the studied soil, but the PTE-loaded capacity of Pb that limits yield was higher than that of Cu. Lead in lettuce roots mainly accumulated in the cell wall (41%), while Cu mainly accumulated in the vacuoles (46%). The Pb and Cu were primarily distributed in the radicle of lettuce seeds under severe PTE stress, resulting in no seed development. Iron plaque formed on the root surface of lettuce seedlings and sequestered Pb and Cu via chelation. At the same concentration, lettuce was less tolerant to Cu in contaminated soil than Pb due to the higher activity of Cu ions in the soil. Lead was more phytotoxic to lettuce than Cu, however, since the radicle emerged from the seed under severe Cu levels, while it did not protrude under severe Pb levels. The potentially damaging effect of Pb in the visually healthy lettuce appeared to be higher than that of Cu under the same soil contamination level.

Impact of Transgenic Arabidopsis thaliana Plants on Herbicide Isoproturon Phytoremediation through Expressing Human Cytochrome P450-1A2

Simple Summary

Isoproturon is one of the best selective herbicide for weed control. Excessive use of herbicides causes many environmental problems. In the present study, phytoremediation of phenylurea isoproturon herbicide using transgenic A. thaliana plants expressing human cytochrome P450-1A2 were investigated. Toxic effect of isoproturon on the plant phenotypic characteristics was explored. The results revealed that no harmful effects appeared on CYP1A2 transgenic plants with high tolerance to isoproturon herbicide applications whereas deleterious effects were observed on the morphological characteristics of the wild type grown in soil under different treatments with isoproturon. The transgenic A. thaliana plants expressing P450-1A2 were able to metabolize the phenylurea herbicide isoproturon. Therefore, this method can be determined as a potential bioremediation agent.

Abstract

The excessive use of herbicides is a major cause of many environmental problems. The use of isoproturon herbicide as a weed controller has been a common practice globally. Phytoremediation technology can help in cleaning up polluted areas. In this paper the ability of CYP1A2 transgenic A. thaliana plants in the phytoremediation of isoproturon herbicides has been investigated. We tested the capability of P450-1A2 overexpression on the detoxification and degradation of isoproturon. We explored the toxic effect of isoproturon on the plant phenotypic characteristics, including the primary root length, rosette diameter, and fresh, dry weight for transgenic and wild type A. thaliana. The results revealed that no morphological changes appeared on CYP1A2 transgenic plants with a high tolerance to isoproturon herbicide applications either via foliar spraying or supplementation of the growth medium. Deleterious effects were observed on the morphological characteristics of plants of the wild type grown in soil under different treatments with isoproturon. The transgenic A. thaliana plants exhibited a vigorous growth even at high doses of isoproturon treatments. In contrast, the growth of the wild type was significantly impaired with doses above 50 µM isoproturon. The transgenic A. thaliana plants expressing P450-1A2 were able to metabolize the phenylurea herbicide isoproturon. Therefore, this method can be determined as a potential bioremediation agent.

Concentration- and nutrient-dependent cellular responses of microalgae Chlorella pyrenoidosa to perfluorooctanoic acid

Perfluorooctanoic acid (PFOA), an emerging and persistent pollutant, could cause toxicity effects on aquatic organisms. However, this was generally assessed under high exposure concentrations of PFOA and nutrient-enriched conditions, which was not accordant with the actual environments. Therefore, to comprehensively understand the toxicity effects of PFOA on aquatic organisms, the cellular responses of microalgae, Chlorella pyrenoidosa, to PFOA under different concentrations (≤ 1.0 mg/L) and nutrient conditions were investigated in this study. Results show that PFOA at concentrations less than 1.0 mg/L had no significant effects on algal growth and chlorophyll contents, and no oxidative damages were generated to destroy membrane integrity and morphology. However, N,P-limited and -starved conditions significantly decreased algal growth and chlorophyll contents, and induced oxidative stresses to ruin the structure and function of cell membrane. Moreover, the deficiency of P had more severe negative effect on algae than that of N, and they both influenced the toxicity responses of microalgae to 1.0 mg/L PFOA. The adsorption and uptake percentages of PFOA by algal cells were both less than 10%, and increased adsorption but decreased uptake of PFOA amounts occurred under N,P-limited and -starved conditions. These findings will be useful to understand the toxicity effects of PFOA on microalgae in aquatic environments.

Pre-harvest glyphosate application and effects on wheat starch chemistry: Analysis from application to harvest

The objective of this study was to determine if the pre-harvest glyphosate application time affects the chemistry of wheat starch. Glyphosate was sprayed at the ripe stage (recommended) and the soft dough stage (early application) of hard red spring wheat. Wheat kernel samples were collected before application and every 3 days until harvest, after which different starch characteristics were analyzed. The results indicate that glyphosate timing does not impact the spatial distribution or morphology of starch granules, as well as the percentage or molecular weight of amylose and amylopectin. However, thermal characteristics of wheat starch, especially when glyphosate was applied at the soft dough stage, showed significant differences. A decrease in the average amylopectin chain length and differences in the proportion of short-, medium-, and long-chain amylopectin was also observed. Overall, this study shows that the pre-harvest application of glyphosate can affect wheat starch chemistry, especially if applied earlier than recommended. PRACTICAL APPLICATIONS: Glyphosate is the most commonly used herbicide in the world, and it is sometimes used pre-harvest during wheat cultivation. The recommended time of application is 7 days prior to harvest when the crops are in the ripe stage of physiological maturity. However, some crops may not be at this stage during application due to non-uniform maturation in the field. The goal of this work was to determine the effect of glyphosate application time (recommended/ripe stage vs. early/soft dough stage) on wheat starch chemistry. The results show that the starch chain length characteristics and thermal behavior are impacted, especially if applied early. Thus, this study shows the importance of timely application to avoid effects on starch chemical properties, which in return could impact starch functionality in food systems. This information is critical in the field of agriculture and to our knowledge this study is one of the first in this area.

Effects of ketoprofen on rice seedlings: Insights from photosynthesis, antioxidative stress, gene expression patterns, and integrated biomarker response analysis

Pharmacologically active compounds found in reclaimed wastewater irrigation or animal manure fertilizers pose potential risks for agriculture. The mechanism underlying the effects of ketoprofen on rice (Oryza sativa L.) seedlings was investigated. The results showed that low concentrations (0.5 mg L^-1) of ketoprofen slightly stimulate growth of rice seedlings, while high concentrations can significantly inhibit growth by reducing biomass and causing damage to roots. Ketoprofen affects photosynthetic pigment content (Chla, Chlb, and carotenoids) and chlorophyll synthesis gene (HEMA, HEMG, CHLD, CHLG, CHLM, and CAO) expression. Fluorescence parameters such as minimum fluorescence (F₀), maximum fluorescence (F_m), variable fluorescence (F_v), potential photosynthetic capacity (F_v/F₀), maximum quantum efficiency of PSII photochemistry (F_v/F_m), electron transfer rate (ETR), and Y(II), Y(NPQ), Y(NO) values were affected, showing photosynthetic electron transfer was blocked. Active oxygen radical (O₂^•-and H₂O₂), malondialdehyde and proline content increased. Superoxide dismutase, catalase and ascorbate peroxidase activities, glutathione content and antioxidant-related gene (FSD1, MSD1, CSD1, CSD2, CAT1, CAT2, CAT3, APX1, APX2) expression were induced. Higher integrated biomarker response values of eight oxidative stress response indexes were obtained at higher ketoprofen concentrations. Ultrastructure observation showed that ketoprofen causes cell structure damage, chloroplast swelling, increase in starch granules, and reduction in organelles. This study provides some suggested toxicological mechanisms and biological response indicators in rice due to stress from pharmacologically active compounds.

Kinetics of inhibition of isoproturon to glutathione-associated enzymes in wheat

The present study aimed at investigating the kinetic of inhibition of isoproturon to the GSH-associated enzymes [γ-glutamyl-cysteine synthetase (γ-GCS), glutathione synthetase (GS), glutathione reductase (GR), glutathione-S-transferase (GST) and glutathione peroxidase (GPX)] in wheat. Isoproturon, applied to 10-day-old seedlings for the following 12 days, provoked significant reductions in shoot fresh and dry weights, protein, thiols and glutathione (GSH); however, oxidized glutathione (GSSG) was elevated while GSH/GSSG ratio was declined with concomitant significant inhibitions in the activities of γ-GCS, GS, GR, GST and GPX; the effect was time dependent. IC50 and Ki values of isoproturon were lowest for GPX, highest for both GST and GR, and moderate for both γ-GCS and GS. The herbicide markedly decreased Vmax of γ-GCS, GS and GPX but unchanged that of GST and GR; however, Km of γ-GCS, GS, GST and GR increased but unchanged for GPX. The pattern of response of changing Vmax, Km, Vmax/Km, kcat and kcat/Km for in vivo and in vitro tests of each enzyme seemed most likely similar. These results indicate that a malfunction to defense system was induced in wheat by isoproturon resulting in inhibitions in GSH-associated enzymes, the magnitude of inhibition was most pronounced in GPX followed by γ-GCS, GS, GST, and GR. These findings could conclude that isoproturon competitively inhibited GST and GR; however, the inhibition was noncompetitive for GPX but mixed for both γ-GCS and GS.

Toxicological responses, bioaccumulation, and metabolic fate of triclosan in Chlamydomonas reinhardtii

Triclosan (TCS) is a broad-spectrum antimicrobial agent that is broadly used in personal care products. It has been shown to cause the contamination of a variety of aquatic environments. Since algae has been the primary producers of aquatic ecosystems, understanding the toxicological mechanisms and the metabolic fate of TCS is vital for assessing its risk in an aquatic environment. In our study, 0.5-4 mg L^-1 TCS treatments for 72 h in a culture of Chlamydomonas reinhardtii (C. reinhardtii) showed progressive inhibition of cell growth and reduced the chlorophyll content. The EC₅₀ value of C. reinhardtii after 72 h was 1.637 mg L^-1, which showed its higher level of resistance to TCS in comparison with other algal species. The exposure to TCS led to oxidative injuries of algae in relation to the increment of malonaldehyde content, cell membrane permeability, and H₂O₂ levels. Furthermore, the oxidative stress from TCS stimulated a series of antioxidant enzyme activities and their gene expressions. Simultaneously, the accumulated TCS in C. reinhardtii arouses the detoxification/degradation-related enzymes and related gene transcriptions. In the medium, approximately 82% of TCS was removed by C. reinhardtii. Importantly, eight TCS metabolites were identified by ultra-performance liquid chromatography-high-resolution mass spectrometry and their relative abundances were measured in a time-course experiment. Six of these metabolites are reported here for the first time. The metabolic pathways of triclosan via C. reinhardtii including reductive dechlorination, hydroxylation, sulfhydrylation, and binding with thiol/cysteine/GSH/glycosyl were manifested to broaden our understanding of the environmental fate of TCS. Graphical Abstract.

A method combining TA cloning and fluorescence screening for rapid acquisition of transgenic seeds

The establishment of transgenic plants has greatly promoted the progress of plant research. However, traditional selection methods using antibiotics or herbicides may miss any positive transformants with growth defects. Additionally, screening with antibiotics/herbicides requires a huge amount of seeds, sterile work conditions and a large amount of space to germinate plants, making the selection process time- and labor-consuming. In this study, we constructed a novel stable transformation vector, plasmid of OLE1-GFP T-DNA vector (pOGT), which can shorten the steps of cloning foreign genes into expression vectors by using TA cloning. Additionally, selection of transformed seeds with fluorescence overcomes the difficulties of conventional selection with antibiotics/herbicides and simplifies the screening process for transgenic plants.

Preharvest Glyphosate Application during Wheat Cultivation: Effects on Wheat Starch Physicochemical Properties

Due to nonuniform maturation, some plants may not be at the recommended stage of maturity when preharvest glyphosate is applied. The objective of this study was to determine how preharvest glyphosate timing affects wheat starch physicochemical properties. Two wheat cultivars were grown in three locations, and glyphosate was applied at the soft dough stage (early application) and the ripe stage (commercial standard). Upon harvest, starch chemical characteristics were studied. The proportion of B-type starch granules was lower in treated samples, although the starch molecular weight was not affected. Rapidly digestible starch content was highest when glyphosate was applied at the ripe stage, and lowest in the control, and vice versa for slowly digestible starch. Additionally, flour pasting viscosity was significantly higher in samples treated at the soft dough stage. Overall, the effects on wheat starch physicochemical characteristics were more pronounced when glyphosate was applied at the soft dough stage of maturity.

Indoor formaldehyde removal by three species of Chlorphytum Comosum under the long-term dynamic fumigation system

Gaseous formaldehyde removal efficiency and physiological characteristics of leaves were investigated through a dynamic fumigation system. Three different species of potted Chlorophytum Comosum, (Green Chlorophytum Comosum for its green leaves), CC (Combined the leaves of Chlorophytum Comosum with leaves half green and half white) and PC (Purple Chlorophytum Comosum for its purple leaves), were exposed to formaldehyde for 7 days. The results showed formaldehyde removal efficiencies in the daytime were 71.07% ± 0.23, 84.66% ± 0.19, and 46.73% ± 0.15 at 1 ppm for GC, CC, and GC plants, respectively, and were 36.21% ± 0.24, 62.15% ± 0.19, and 34.97% ± 0.11 at night. This might be due to higher plant physiological activities (e.g., photosynthesis, respiration, and transpiration) during the daytime than at night. Ten physiological indicators of leaves were chosen to evaluate the 7-day fumigation process, which were chlorophyll, free protein, relative conductivity, malondialdehyde (MDA), hydrogen peroxide (H₂O₂), hydroxyl radical, superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and total antioxidant capacity (T-AOC). Eight of these indicators increased, while chlorophyll decreased by 22.16%, 6.95%, and 25.32%, and CAT decreased by 18.9%, 17.8%, and 25.30% for GC, CC, and PC respectively. Among all the increasing physiological indicators, relative conductivity and MDA showed the greatest increase by 279.32% and 155.56% for PC. A 15-day recovery study was also conducted using MDA and T-AOC as indicators. The results showed that all the tested plants could be tolerant up to the 8 ppm of formaldehyde concentration for 7 days under dynamic fumigation and needed 10-15 days for self-recovery.

Uptake of atrazine in a paddy crop activates an epigenetic mechanism for degrading the pesticide in plants and environment

There is a rising public concern on accumulation of harmful pesticides in environment and crops. Epigenetic alteration caused by environmental contaminants is one of the key factors in the etiology of environmentally-associated diseases. Growing evidence shows that harmful pesticide atrazine (ATZ) has a profound effect on DNA methylation in human genome, however, little is known about the epigenetic mechanism underlying ATZ accumulation and degradation in plants, particularly in edible plants growing in the ATZ-contaminated areas. This study investigated the atrazine elimination that was mediated by DNA methylation and histone modification in the food crop rice. Studies with two mutant Osmet1-1/2 defective in the genomic CG DNA methylation show significantly lower accumulation of atrazine than its wild-types. Profiling methylome and transcriptome of ATZ-exposed Osmet1 and wild-type identified many differentially methylated loci (≥2 fold change, p < 0.05), which were associated with activation of genes responsible for atrazine degradation in plants. Three demethylated loci OsGTF, OsHPL1 and OsGLH were expressed in eukaryotic yeast cells and found to eliminate a marked proportion of ATZ in growth environments by 48%, 43% and 32%, respectively, whereas the increased ATZ-degraded products were characterized using UPLC/Q-TOF-MS/MS. These results suggest that activation of the loci mediated by ATZ-induced hypomethylation could be responsible for the removal of ATZ in rice. Our work helps understand a new regulatory mechanism underlying the atrazine degradation in crops which may potentially reduce the environmental risks to human health through food chain.

Phytotoxicity assessment of isoproturon on growth and physiology of non-targeted aquatic plant Lemna minor L. - A comparison of continuous and pulsed exposure with equivalent time-averaged concentrations

Phenylurea herbicides are often present in the aquatic ecosystems and may be accumulated by the non-targeted organisms and impose a negative effect on the organism and the community. This study aims to investigate and compare the effects of two different isoproturon (IPU) pulse exposure scenarios on the non-targeted aquatic plant Lemna minor with effects observed in the standard test with continuous exposure. The obtained results showed that continuous IPU treatment causes significant reduction of photosynthetic pigment concentration and proteins as well as inhibition of L. minor growth. The activities of CAT, G-POX, and APX were significantly induced to diminish the accumulation of ROS under IPU treatment, but the induction of antioxidant enzymes was not sufficient to protect the plants from herbicide-induced oxidative stress. The growth of L. minor under pulse exposure to IPU recovers fast, but pulse treatment results in significant physiological changes in treated plants. The accumulation of H₂O₂ and lipid peroxidation products, alongside the reduced concentration of proteins and photosynthetic pigments in pulse treatment after a recovery period, indicates that IPU causes prolonged oxidative stress in L. minor plants. The recovery potential of L. minor plants after treatment with herbicides may have an important role in maintaining the population of essential primary producers in aquatic ecosystems, but IPU-induced physiological changes could potentially have a significant role in modulating the response of the plants to the next exposure event.

Uptake, accumulation and metabolization of 1-butyl-3-methylimidazolium bromide by ryegrass from water: Prospects for phytoremediation

The unique properties of ionic liquids make them attractive for a wide range of industrial applications, which makes it easy to be released into the environment and cause water or soil pollution. Phytoremediation of organic contaminants is a safe and important process for removing persistent pollutants from the environment. However, due to they are very chemically stable and potentially toxic to plants, whether they can be removed, assimilated and metabolized by plants remains unknown during phytoremediation process. In this study, ryegrass, Lolium perenne L., was used for imidazolium ionic liquid (1-butyl-3-methylimidazolium bromide, [C₄mim]⁺) removal from water. The results show that [C₄mim]⁺ could be taken up, accumulated and metabolized by plants in vivo with a high removal efficiency. Most of the [C₄mim]⁺ was accumulated in the root tissue, with the root concentration fraction factors ranging from 4.9 to 51.5. Two hydroxylated metabolites 1-(4-hydroxybutyl)-3-methylimidazolium, and 1-(n-butyl)-3-(hydroxymethyl)-imidazolium, and two secondary metabolites were detected in the ryegrass after [C₄mim]⁺ uptake. The metabolic mechanism was clarified using density functional theory calculations. Furthermore, [C₄mim]⁺ at a high concentration was found to be high toxic to inhibit the growth of ryegrass markedly. In response, some oxidative stress was observed in the metabolic process, as indicated by increasing of catalase, super dismutase and peroxidase activities. Our results suggested that phytoremediation was an efficient technique for ionic liquids treatment from water.

Biodegrading Two Pesticide Residues in Paddy Plants and the Environment by a Genetically Engineered Approach

Accumulating pesticide (and herbicide) residues in soils have become a serious environmental problem. This study focused on identifying the removal of two widely used pesticides, isoproturon (IPU) and acetochlor (ACT), by a genetically developed paddy (or rice) plant overexpressing an uncharacterized glycosyltransferase (IRGT1). IRGT1 conferred plant resistance to isoproturon-acetochlor, which was manifested by attenuated cellular injury and alleviated toxicity of rice under isoproturon-acetochlor stress. A short-term study showed that IRGT1-transformed lines removed 33.3-48.3% of isoproturon and 39.8-53.5% of acetochlor from the growth medium, with only 59.5-72.1 and 58.9-70.4% of the isoproturon and acetochlor remaining in the plants compared with the levels in untransformed rice. This phenotype was confirmed by IRGT1-expression in yeast ( Pichia pastoris) which grew better and contained less isoproturon-acetochlor than the control cells. A long-term study showed that isoproturon-acetochlor concentrations at all developmental stages were significantly lower in the transformed rice, which contain only 59.3-69.2% (isoproturon) and 51.7-57.4% (acetochlor) of the levels in wild type. In contrast, UPLC-Q-TOF-MS/MS analysis revealed that more isoproturon-acetochlor metabolites were detected in the transformed rice. Sixteen metabolites of isoproturon and 19 metabolites of acetochlor were characterized in rice for Phase I reactions, and 9 isoproturon and 13 acetochlor conjugates were characterized for Phase II reactions in rice; of these, 7 isoproturon and 6 acetochlor metabolites and conjugates were reported in plants for the first time.

Oxidative stress caused by Basagran® herbicide is altered by salicylic acid treatments in peanut plants

The present work was to study a protective role of salicylic acid (SA) on oxidative stress caused by Basagran® herbicide application. Two peanut cultivars (Arachis hypogaea cv. Giza 5 and Giza 6) with different sensitivities to the herbicide were monitored for their antioxidant responses to Basagran® and/or SA treatments. Two weeks after treatment, Basagran® lowered leaf pigments (Chlorophyll a, Chlorophyll b and total Carotenoids) but increased hydrogen peroxide (H2O2) and malondialdehyde (MDA) contents indicating occurrence of lipid peroxidation and oxidative stress. Salicylic acid applied prior to low dose Basagran® lowered H2O2 and MDA contents in both G5 and G6. Except for SOD which is highly stimulated, POD, CAT and APX activities showed slight changes compared to control in leaves treated with Basagran® ± SA. The extracts tested by DPPH showed increase in total antioxidant activity by 4%-7% in SA + Basagran® treated leaves compared to control. The increased total antioxidant activity was related to the accumulation of amounts of phenolics as a protective action stimulated by SA. Alterations of antioxidant enzymatic system, accumulation of phenolics, increasing the total antioxidant activity by SA provide an evidence of protective action of SA in Basagran® detoxification.

Enantiomeric impacts of two amide chiral herbicides on Echinochloa crus-galli physiology and gene transcription

Echinochloa crus-galli is one of the most noxious weeds in the world and causes yield losses in a variety of different field crops. Napropamide and acetochlor are herbicides commonly employed to control this weed. Both compounds are chiral, with enantiomers displaying different activities. However, it is unclear how the enantiomers of these two chiral herbicides act on different tissues of E. crus-galli. The objective of this paper is to investigate the action mechanism of napropamide and acetochlor in the roots and shoots of E. crus-galli. R‑enantiomers were found to be more active than either the racemates or S-enantiomers on the weed. The content of chlorophyll was not significantly affected by treatment with either enantiomer. The impacts on the activity for the oxidative stress enzymes, except catalase (CAT), showed that both napropamide and acetochlor enantiomers could induce oxidative stress. Furthermore, R‑enantiomers caused greater oxidative damage. Enhanced glutathione-S-transferase (GST) activity and expression of GST genes suggested both EcGSTF1 and EcGSTZ1 were present in the roots and shoots, and this will be helpful for detoxification. The changes in both the roots and shoots revealed the two herbicides displayed tissue selectivity in E. crus-galli. These results enable a better understanding on the mechanism of action for napropamide and acetochlor enantiomers on different tissues, including the shoots and roots in E. crus-galli.

Isoproturon-Induced Salicylic Acid Confers Arabidopsis Resistance to Isoproturon Phytotoxicity and Degradation in Plants

This study identified the effect of salicylic acid on degradation of isoproturon in Arabidopsis. Three T-DNA insertion mutant lines pal1- 1, pal1- 2, and eps1- 1 defective in salicylic acid synthesis were tested, which showed higher isoproturon accumulation and a toxic symptom in the mutants. When treated with 5 mg/L salicylic acid, these lines displayed a lower level of isoproturon and showed an attenuated toxic symptom. An RNA-sequencing study identified 2651 (1421 up and 1230 down) differentially expressed genes (DEGs) in eps1- 1 and 2211 (1556 up and 655 down) in pal1- 2 mutant plants (>2.0 fold change, p < 0.05). Some of the DEGs covered Phase I-III reaction components, like glycosyltransferases (GTs) and ATP-binding cassette transporters (ABCs). Using ultra performance liquid chromatography-time-of-flight-tandem-mass spectrometer/mass spectrometer (UPLC/Q-TOF-MS/MS), 13 Phase I and four Phase II metabolites were characterized. Of these, two metabolites 1-OH-isopropyl-benzene-O-glucoside and 4-isopropylphenol-S-2-methylbutanoyl-serine, have been identified and reported for the first time.

Screening of candidate gene responses to cadmium stress by RNA sequencing in oilseed rape (Brassica napus L.)

Cadmium (Cd) stress is one of the most serious threats to agriculture in the world. Oilseed rape (Brassica napus L.) is an important oil crop; however, Cd can easily accumulate in rapeseed and thus harm human health through the food chain. In the first experiment, our purpose was to measure the Cd accumulation in mature B. napus plants and its influences on fatty acid composition. The results showed that most Cd was accumulated in the root, and the seed fatty acid content was considerably different at different Cd toxicity levels. In the second experiment, 7-day-old B. napus seedlings stressed by Cd (1 mM) for 0 h (CK-0h), 24 h (T-24h), or 72 h (T-72h) were submitted to physiological and biological analyses, RNA-Seq and qRT-PCR. In total, 5469 and 6769 differentially expressed genes (DEGs) were identified in the comparisons of "CK-0h vs T-24h" and "CK-0h vs T-72h", respectively. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses showed that the photosynthetic and glutathione (GSH) pathways were significantly enriched in response to Cd stress. Key factors in the response to Cd stress included BnPCS1, BnGSTU12, BnGSTU5, and BnHMAs. The transcription factors BnWRKY11 (BnaA03g51590D), BnWRKY28 (BnaA03g43640D), BnWRKY33 (BnaA03g17820D), and BnWRKY75 (BnaA03g04160D) were upregulated after Cd exposure. The present study revealed that upregulation of the genes encoding GST and PCS under Cd stress promoted the formation of low-molecular weight complexes (PC-Cd), and upregulation of heavy metal ATPase genes induced PC-Cd transfer to vacuoles. These findings may provide the basis for the molecular mechanism of the response of B. napus to Cd.

Monitoring the stress resistance of Pennisetum purpureum in Pb (II) contaminated soil bioaugmented with Enterobacter cloacae as defence strategy

Lead (Pb) is reported to have negative effects on the biogeochemical behaviour of the plant growth. In recent years, the significance of rhizoremediation of heavy metals has been of great focus aiding in the development rates of plants under stressed conditions. The present study evaluated the physio-biochemical response of Pennisetum purpureum to different concentrations of Pb (II) viz., 0, 50, 100 and 150 mg kg^-1 in the form of lead (II) nitrate. The pre-characterized PGPR strain, Enterobacter cloacae - KU598849 was used to augment the plants. After Pb exposure for 45 d, parameters such as plant growth, lead accumulation, H₂O₂ content, MDA content, protein, proline content and antioxidant enzymatic activities were quantified. Results illustrated that increasing Pb concentration reduced the early growth, metal accumulation, protein content and affected physio-biochemical changes by causing oxidative damage in plants. Upon augmentation of the bacterial inoculum, the plants significantly resisted the toxic effects of Pb. Increased Pb bioaccumulation pattern was recorded in roots than shoots, were highest uptake was found to be 72 mg kg^-1 dry weight when exposed to 150 mg kg^-1 Pb concentration. Lead supplementation increased the activities of malonylaldehyde (MDA), superoxide dismutase (SOD), peroxidase (POX), ascorbate peroxidase (APX) and catalase (CAT) in P. purpureum. Bacterial bioaugmentation resulted in the reduction of the oxidative stress aided with reduced antioxidant enzyme activities indicating the minimization of the damages under stress.

Reduced phytotoxicity of propazine on wheat, maize and rapeseed by salicylic acid

Propazine belongs to the triazine herbicide family and widely used in the farmland for crop production. Recent studies have shown that the residue of propazine in environment is accumulative. This inevitably results in accumulation of propazine in crops. Therefore, reduction of propazine toxicity and accumulation in crops is critically important. In this study, the growth of wheat, maize and rapeseed was significantly inhibited by 2, 8 and 0.4 mg kg^-1 propazine in soils. The chlorophyll content of the three crops also showed significant decrease, while the electrolyte permeability, a biomarker of cellular damage, increased in the plant cells. However, when plants were sprayed with 5 mg L^-1 of salicylic acid (SA), the propazine phytotoxicity of the crops was relieved, with increased chlorophyll content and reduced electrolyte permeability of all crops. Meanwhile, the activities of peroxidase (POD) and glutathione transferase (GST) remained lower. The propazine accumulation in the crops and the residues in the soil were determined by high performance liquid chromatography. The concentration of propazine in plants and soils treated by SA was less than that of the untreated control. Six propazine degraded products (derivatives) in rhizosphere of wheat were characterized using ultraperformance liquid chromatography with a quadrupole-time-of-flight tandem mass spectrometer. Our work indicates that the improved growth of crops was possibly due to the acceleration of propazine degradation by salicylic acid.

Physiological and molecular responses of pearl millet seedling to atrazine stress

Pearl millet has been recommended beneficial for several therapeutic purposes. However, little is known of the physiological responses to abiotic stressors, especially of atrazine. In order to elucidate the physiological and molecular responses of pearl millet to atrazine stress, we studied the response of various biomarkers under increasing herbicide concentrations (0, 5, 10, and 50 mg/kg). We also quantified the levels of malondialdehyde (MDA) and reactive oxygen species (ROS) (H₂O₂ and O₂•^-) produced in the leaves to evaluate the extent of oxidative damage. Increasing atrazine concentrations significantly increased ROS and MDA production in the plant leaves. Ascorbate peroxidase (APX) and peroxidase (POD) activities increased, while catalase (CAT) and superoxide dismutase activities reduced with increasing atrazine concentrations. Generally, atrazine applied at 50 mg/kg suppressed chlorophyll contents, whereas, chlorophyll (a/b) ratio was increased. Atrazine applied at 50 mg/kg significantly suppressed antioxidant gene expressions to the lowest. The APX gene showed overall low response to the atrazine treatments. The chloroplastic psbA gene showed highest expression with 10 mg/kg atrazine, whereas atrazine at 50 mg/kg significantly suppressed the gene expression to its lowest. Pearl millet was able to suppress oxidative stress under low atrazine levels, but high atrazine concentration could induce more oxidative damage.

Evaluation of the Removal of Potassium Cyanide and its Toxicity in Green Algae (Chlorella vulgaris)

To evaluate the removal of potassium cyanide (KCN) and its toxicity in algae, an initial comprehensive analysis was performed with Chlorella vulgaris. The algae showed potential removal capability for KCN, with the maximal removal rate of 61%. Moreover, effects of KCN on growth, cellular morphology and antioxidant defense system of C. vulgaris were evaluated. Cell number and chlorophyll a content decreased in most cases, with the maximal inhibition rates of 48% and 99%, respectively. The 100 mg L^- 1 KCN seriously damaged the algal cell membrane. Additionally, activity of superoxide dismutase (SOD) was promoted by KCN exposure among 0.1-50 mg L^- 1 and inhibited by 100 mg L^- 1 KCN, while the malondialdehyde (MDA) content gradually decreased in C. vulgaris with increasing exposure concentration compared to the control. The present study reveals that C. vulgaris is useful in bio-treatment of cyanide-contaminated aquatic ecosystem, except in high concentrations which would cause overwhelming effects.

Degrading and Phytoextracting Atrazine Residues in Rice (Oryza sativa) and Growth Media Intensified by a Phase II Mechanism Modulator

Atrazine (ATZ) residue in farmland is one of the environmental contaminants seriously affecting crop production and food safety. Understanding the regulatory mechanism for ATZ metabolism and degradation in plants is important to help reduce ATZ potential toxicity to both plants and human health. Here, we report our newly developed engineered rice overexpressing a novel Phase II metabolic enzyme glycosyltransfearse1 (ARGT1) responsible for transformation of ATZ residues in rice. Our results showed that transformed lines, when exposed to environmentally realistic ATZ concentration (0.2-0.8 mg/L), displayed significantly high tolerance, with 8-27% biomass and 36-56% chlorophyll content higher, but 37-69% plasma membrane injury lower than untransformed lines. Such results were well confirmed by ARGT1 expression in Arabidopsis. ARGT1-transformed rice took up 1.6-2.7 fold ATZ from its growth medium compared to its wild type (WT) and accumulated ATZ 10%-43% less than that of WT. A long-term study also showed that ATZ in the grains of ARGT1-transformed rice was reduced by 30-40% compared to WT. The ATZ-degraded products were characterized by UPLC/Q-TOF-MS/MS. More ATZ metabolites and conjugates accumulated in ARGT1-transformed rice than in WT. Eight ATZ metabolites for Phase I reaction and 10 conjugates for Phase II reaction in rice were identified, with three ATZ-glycosylated conjugates that have never been reported before. These results indicate that ARGT1 expression can facilitate uptake of ATZ from environment and metabolism in rice plants.

Accumulation efficiency, genotoxicity and antioxidant defense mechanisms in medicinal plant Acalypha indica L. under lead stress

The present study was designed to assess the physiological and biochemical changes in roots and shoots of the herb Acalypha indica grown under hydroponic conditions during exposure to lead (Pb) (100-500 mg L^-1) for 1-12 d. The accumulation of Pb by A. indica plants was found to be 121.6 and 17.5 mg g^-1 dry weight (DW) in roots and shoots, respectively, when exposed to a Pb concentration of 500 mg L^-1. The presence of Pb ions in stem, root and leaf tissues was confirmed by scanning electron microscope (SEM) and Energy-dispersive X-ray spectroscopy (EDX) analyses. Concerning the activity of antioxidant enzymes, viz., peroxidase (POX) catalase (CAT) and ascorbate peroxidase (APX), they were induced at various regimes during 5, 8 and 12 d of Pb exposure in both the leaves and roots than untreated controls. Lead treatment increased superoxide dismutase (SOD) activity in both the leaf and root tissues over control, irrespective of the duration of exposure. Anew, it was observed that Pb treatments induced variations in the number and intensity of protein bands. Random amplified polymorphic DNA (RAPD) results show that the Pb treatment caused genotoxicity on DNA molecules as evidenced by the amplification of new bands and the absence of normal DNA amplicons in treated plants. Results confirm that A. indica is a Pb accumulator species, and the antioxidants might play a crucial role in the detoxification of Pb-induced toxic effects.

Exogenous salicylic acid alleviates the toxicity of chlorpyrifos in wheat plants (Triticum aestivum)

The role of exogenous salicylic acid (SA) in protecting wheat plants (Triticum aestivum) from contamination by the insecticide chlorpyrifos was investigated in this study. The wheat plants were grown in soils with different concentrations (5, 10, 20, and 40mgkg^-1) of chlorpyrifos. When the third leaf emerged, the wheat leaves were sprayed with 1, 2, 4, 8, and 16mgL^-1 of SA once a day for 6 days. The results showed that wheat exposed to higher concentrations of chlorpyrifos (≥20mgkg^-1) caused declines in growth and chlorophyll content and altered the activities of a series of antioxidant enzymes including superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), and ascorbate peroxidase (APX). Interestingly, treatments with different concentrations of SA mitigated the stress generated by chlorpyrifos and improved the measured parameters to varying degrees. Furthermore, a reverse transcription and quantitative PCR experiment revealed that the activities of SOD and CAT can be regulated by their target gene in wheat when treated with SA. We also found that SA is able to block the accumulation of chlorpyrifos in wheat. However, the effect of SA was related to its concentration. In this study, the application of 2mgL^-1 of SA had the greatest ameliorating effect on chlorpyrifos toxicity in wheat plants.

Short-term phytotoxicity in Brassica napus (L.) in response to pre-emergently applied metazachlor: A microcosm study

In accordance with realistic application approaches, a short-term 1-factorial experiment was set up to investigate the phytotoxic impact of pre-emergent application of the chloroacetamide herbicide metazachlor on Brassica napus. In addition to morphological parameters, the underlying processes that ultimately determine the extent of herbicide-induced phytotoxicity (i.e., herbicide metabolization and cellular antioxidant defense) were examined. The present study demonstrated that metazachlor provoked fasciation of the leaves closely after emergence, which might be linked to its mode of action whereby cell division is impaired through the inhibition of very long chain fatty acid synthesis. The increased activities of antioxidative enzymes and metabolites in leaf tissue indicated the presence of reactive oxygen species under the influence of metazachlor. This resulted in oxidative damage in the form of membrane lipid peroxidation. Simultaneously, the increased activity of glutathione S-transferase and the shift in glutathione redox state suggested activation of the detoxification metabolism. This occurred, however, at the expense of growth, with a temporary reduction in plant height and weight after application. The results indicated that metazachlor disappeared within 3 mo to 4 mo after application, which resulted in the recovery of the crop. In conclusion, metazachlor induces phytotoxicity in the short term, either directly through its mode of action or indirectly through the induction of oxidative stress, which resulted in a temporary reduction in growth. Environ Toxicol Chem 2017;36:59-70. © 2016 SETAC.

Selective Effect of Pesticides on Plant--A Review

This review represents systematic and integrated picture of pesticide exposure to plant and its effect on growth and metabolism. Decades ago, agrochemicals were introduced aiming at enhancing crop yields and protecting crops from pests. Due to adaptation and resistance developed by pests to chemicals, every year higher amounts and new chemical compounds are used to protect crops, causing undesired side effects and raising the costs of food production. Biological chemical free agriculture is gaining also more and more support but it is still not able to respond to the need for producing massive amounts of food. The use of agrochemicals, including pesticides, remains a common practice especially in tropical regions and South countries. Cheap compounds, such as DDT, HCH, and Lindane, that are environmentally persistent, are today banned from agriculture use in developed countries, but remain popular in developing countries. As a consequence, persistent residues of these chemicals contaminate food and disperse in the environment. Therefore, the thrust of this paper was to review the application of pesticides effect early from germination to growth of the plant, leading to alteration in biochemical, physiological and different enzymatic and non-enzymatic antioxidants which ultimately affect the yield and resulted in residues in plant, vegetables, and fruits.

Comparative toxicity of nonylphenol, nonylphenol-4-ethoxylate and nonylphenol-10-ethoxylate to wheat seedlings (Triticum aestivum L.)

Nonylphenol polyethoxylates (NPEOs) are a group of surfactants that are widely used in industrial and household products and often detected in the environment. The metabolite of NPEOs, named nonylphenol (NP), has proven to be an endocrine disruptor, and its environmental behavior and eco-toxicity have been widely investigated in previous studies. However, to the best of our knowledge, insight into the toxicity differences of NP and NPEOs on important crops remains limited. Therefore, this study investigated the comparative toxicity of NP, nonylphenol-4-ethoxylate (NP4EO), and nonylphenol-10-ethoxylate (NP10EO) on wheat seedlings using hydroponic experiments. The results indicated that NP is most toxic to wheat followed by NP4EO, and NP10EO is the least toxic to wheat. The adverse effects of NP on wheat were observed for all the tested parameters including germination, shoot length, root length, chlorophyll, lipid peroxidation, and enzymatic activities. To gain insight into the molecular response, we analyzed the transcript abundance of SOD-Cu/Zn and CAT with NP, NP4EO, and NP10EO exposure using quantitative real-time PCR. The data revealed that both genes exhibited up- or down-regulated expression patterns that were consistent with the activities of the two enzymes. This result further conformed that NP is most toxic to wheat plants.

Perspectives of using fungi as bioresource for bioremediation of pesticides in the environment: a critical review

Pesticides are used for controlling the development of various pests in agricultural crops worldwide. Despite their agricultural benefits, pesticides are often considered a serious threat to the environment because of their persistent nature and the anomalies they create. Hence removal of such pesticides from the environment is a topic of interest for the researchers nowadays. During the recent years, use of biological resources to degrade or remove pesticides has emerged as a powerful tool for their in situ degradation and remediation. Fungi are among such bioresources that have been widely characterized and applied for biodegradation and bioremediation of pesticides. This review article presents the perspectives of using fungi for biodegradation and bioremediation of pesticides in liquid and soil media. This review clearly indicates that fungal isolates are an effective bioresource to degrade different pesticides including lindane, methamidophos, endosulfan, chlorpyrifos, atrazine, cypermethrin, dieldrin, methyl parathion, heptachlor, etc. However, rate of fungal degradation of pesticides depends on soil moisture content, nutrient availability, pH, temperature, oxygen level, etc. Fungal strains were found to harbor different processes including hydroxylation, demethylation, dechlorination, dioxygenation, esterification, dehydrochlorination, oxidation, etc during the biodegradation of different pesticides having varying functional groups. Moreover, the biodegradation of different pesticides was found to be mediated by involvement of different enzymes including laccase, hydrolase, peroxidase, esterase, dehydrogenase, manganese peroxidase, lignin peroxidase, etc. The recent advances in understanding the fungal biodegradation of pesticides focusing on the processes, pathways, genes/enzymes and factors affecting the biodegradation have also been presented in this review article.

Rice (Oryza sativa) Laccases Involved in Modification and Detoxification of Herbicides Atrazine and Isoproturon Residues in Plants

Atrazine (ATR) and isoproturon (IPU) as herbicides have become serious environmental contaminants due to their overuse in crop production. Although ATR and IPU in soils are easily absorbed by many crops, the mechanisms for their degradation or detoxification in plants are poorly understood. This study identified a group of novel genes encoding laccases (EC 1.10.3.2) that are possibly involved in catabolism or detoxification of ATR and IPU residues in rice. Transcriptome profiling shows at least 22 differentially expressed laccase genes in ATR/IPU-exposed rice. Some of the laccase genes were validated by RT-PCR analysis. The biochemical properties of the laccases were analyzed, and their activities in rice were induced under ATR/IPU exposure. To investigate the roles of laccases in degrading or detoxifying ATR/IPU in rice, transgenic yeast cells (Pichia pastoris X-33) expressing two rice laccase genes (LOC_Os01g63180 and LOC_Os12g15680) were generated. Both transformants were found to accumulate less ATR/IPU compared to the control. The ATR/IPU-degraded products in the transformed yeast cells using UPLC-TOF-MS/MS were further characterized. Two metabolites, hydroxy-dehydrogenated atrazine (HDHA) and 2-OH-isopropyl-IPU, catalyzed by laccases were detected in the eukaryotic cells. These results indicate that the laccase-coding genes identified here could confer degradation or detoxification of the herbicides and suggest that the laccases could be one of the important enzymatic pathways responsible for ATR/IPU degradation/detoxification in rice.

The functional role of the photosynthetic apparatus in the recovery of Brassica napus plants from pre-emergent metazachlor exposure

Metazachlor is a chloroacetamide herbicide, frequently used in Brassica napus cultivations around the world. Its primary target is the inhibition of very long chain fatty acid biosynthesis. This study included a morphological and physiological screening of hydroponically grown B. napus, exposed to a concentration range of 0, 0.25, 0.50, 0.75 and 1.0kg metazachlor per hectare. The results indicate that within a month after application, growth and development of B. napus are severely affected by low metazachlor doses. At intermediate metazachlor concentrations, loss of phosphorous and potassium from the plant tissues suggests destabilisation of cellular membranes, which may be a direct consequence of metazachlor application. This membrane instability could be indirectly linked with alterations of electron transport and a reduction of carbon assimilation. At increased metazachlor doses of 0.75kga.i.ha(-1), pigment concentrations are strongly reduced. However, chlorophyll fluorescence parameters seem to remain unaffected at metazachlor doses up to 0.75kga.i.ha(-1). At a metazachlor concentration of 1.0kga.i.ha(-1), negative effects are observed on all tested parameters, resulting in limited survival. The results indicate photosynthesis is assured at intermediate metazachlor concentrations for the cost of growth and development. It is clear that photosynthesis plays a key role in the survival strategy of young plants to overcome initially induced chemical stress.