Metazachlor effect on poplar - Pioneer plant species for riparian buffers

Chemical Composition, Antibacterial Activity and Mechanism of Action of Fermentation Products from Aspergillus Niger xj

Six compounds were isolated and purified from the crude acetone extract of Aspergillus niger xj. Characterization of all compounds was done by NMR and MS. On the basis of chemical and spectral analysis structure, six compounds were elucidated as metazachlor (1), nonacosane (2), palmitic acid (3), 5,5'-oxybis(5-methylene-2-furaldehyde) (4), dimethyl 5-nitroisophthalate (5) and cholesta-3,5-dien-7-one (6), respectively, and compounds 1, 4, 5 and 6 were isolated for the first time from A. niger. To evaluate the antibacterial activity of compounds 1-6 against three plant pathogenic bacteria (Agrobacterium tumefaciens T-37, Erwinia carotovora EC-1 and Ralstonia solanacearum RS-2), and the minimum inhibitory concentrations (MICs) were determined by broth microdilution method in 96-well microtiter plates. Results of the evaluation of the antibacterial activity showed that T-37 strain was more susceptible to metazachlor with the lowest MIC of 31.25 µg/mL. The antibacterial activity of metazachlor has rarely been reported, thus the antibacterial mechanism of metazachlor against T-37 strain were investigated. The permeability of cell membrane demonstrated that cells membranes were broken by metazachlor, which caused leakage of ions in cells. SDS-PAGE of T-37 proteins indicated that metazachlor could damage bacterial cells through the destruction of cellular proteins. Scanning electron microscopy results showed obvious morphological and ultrastructural changes in the T-37 cells, further confirming the cell membrane damages caused by metazachlor. Overall, our findings demonstrated that the ability of metazachlor to suppress the growth of T-37 pathogenic bacteria makes it potential biocontrol agents.

Selection of aquatic microbiota exposed to the herbicides flufenacet and metazachlor

Herbicides are important, ubiquitous environmental contaminants, but little is known about their interaction with bacterial aquatic communities. Here, we sampled a protected natural freshwater habitat and characterised its microbiome in interaction with herbicides. We evolved the freshwater microbiomes in a microcosm assay of exposure (28 days) to flufenacet and metazachlor at environmental concentrations of 0.5, 5 and 50 μg L-1 . Inhibitory effects of herbicides were exemplarily assessed in cultured bacteria from the same pond (Pseudomonas alcaligenes, Paenibacillus amylolyticus and Microbacterium hominis). Findings were compared to long-term concentrations as provided by local authorities. Here, environmental concentrations reached up to 11 μg L-1 (flufenacet) and 76 μg L-1 (metazachlor). Bacteria were inhibited at minimum inhibitory concentrations far above these values; however, concentrations of 50 μg L-1 of flufenacet resulted in measurable growth impairment. While most herbicide-exposed microcosm assays did not differ from controls, Acidobacteria were selected at high environmental concentrations of herbicides. Alpha-diversity (e.g., taxonomic richness on phylum level) was reduced when aquatic microbiomes were exposed to 50 μg metazachlor or flufenacet. One environmental strain of P. alcaligenes showed resistance to high concentrations of flufenacet (50 g L-1 ). In total, this study reveals that ecologic imbalance due to herbicide use significantly impacts aquatic microbiomes.

The Impact of Pesticide Use on Tree Health in Riparian Buffer Zone

The result of the enormous usage of pesticides in agriculture is the contamination of soil and water bodies surrounding the fields. Therefore, creating buffer zones to prevent water contamination is very useful. Chlorpyrifos (CPS) is the active substance of a number of insecticides widely used all over the world. In our study, we focused on the effect of CPS on plants forming riparian buffer zones: poplar (Populus nigra L., TPE18), hybrid aspen (P.tremula L. × P. tremuloides Michx.), and alder (Alnus glutinosa L.). Foliage spray and root irrigation experiments were conducted under laboratory conditions on in vitro cultivated plants. Spray applications of pure CPS were compared with its commercially available form-Oleoekol^®. Although CPS is considered a nonsystemic insecticide, our results indicate that CPS is transferred not only upwards from roots to shoots but also downwards from leaves to roots. The amount of CPS in the roots was higher (4.9 times and 5.7 times, respectively) in aspen or poplar sprayed with Oleoekol than in those sprayed with pure CPS. Although the treated plants were not affected in growth parameters, they showed increased activity of antioxidant enzymes (approximately two times in the case of superoxide dismutase and ascorbate peroxidase) and augmented levels of phenolic substances (control plants -114.67 mg GAE/g dry tissue, plants treated with CPS-194.27 mg GAE/g dry tissue). In summary, chlorpyrifos, especially as a foliar spray pesticide, can create persistent residues and affects not only target plants but also plants surrounding the field.

A novel approach for measuring membrane permeability for organic compounds via surface plasmon resonance detection

Well-known methods for measuring permeability of membranes include static or flow diffusion chambers. When studying the effects of organic compounds on plants, the use of such model systems allows to investigate xenobiotic behavior at the cuticular barrier level and obtain an understanding of the initial penetration processes of these substances into plant leaves. However, the use of diffusion chambers has disadvantages, including being time-consuming, requiring sampling, or a sufficiently large membrane area, which cannot be obtained from all types of plants. Therefore, we propose a new method based on surface plasmon resonance imaging (SPRi) to enable rapid membrane permeability evaluation. This study presents the methodology for measuring permeability of isolated cuticles for organic compounds via surface plasmon resonance detection, where the selected model analyte was the widely used pesticide metazachlor. Experiments were performed on the cuticles of Ficus elastica, Citrus pyriformis, and an artificial PES membrane, which is used in passive samplers for the detection of xenobiotics in water and soils. The average permeability for metazachlor was 5.23 × 10^-14 m² s^-1 for C. pyriformis, 1.34 × 10^-13 m² s^-1 for F. elastica, and 7.74 × 10^-12 m² s^-1 for the PES membrane. We confirmed that the combination of a flow-through diffusion cell and real-time optical detection of transposed molecules represents a promising method for determining the permeability of membranes to xenobiotics occurring in the environment. This is necessary for determining a pesticide dosage in agriculture, selecting suitable membranes for passive samplers in analytics, testing membranes for water treatment, or studying material use of impregnated membranes.

Sex-Specific Physiological Responses of Populus cathayana to Uranium Stress

Attention is increasingly being paid to the contamination of soil by the radioactive element uranium (U). Phytoremediation of contaminated soil by economically advantageous and environment-protective plants shows considerable potential for addressing this problem. Populus cathayana is a species with high heavy-metal tolerance, economic value, and notable potential for phytoremediation. Plant-sex-related differences can lead to differences in vegetative growth and tolerance to various stressors. As such, in this study, we designed a pot experiment to analyze the responses of male and female trees of P. cathayana to 50 mg kg−1 U stress in contaminated soil for 3 months. We studied the U uptake and distribution, photosynthesis, chlorophyll fluorescence, active oxygen species, and antioxidant enzymes of P. cathayana. The results showed that the photosynthetic activity and chlorophyll fluorescence of male and female trees were similar, and U stress mainly affected the nonstomatal factors and photosystem II during photosynthesis. Regarding the physiological and biochemical processes, male and female trees showed different defense strategies: male trees had higher peroxidase (POD), H2O2, and soluble sugars, but lower malondialdehyde (MDA), superoxide dismutase (SOD), and soluble proteins. Under U stress, the active oxygen produced by male trees could be cleared by antioxidant enzymes, preventing damage to the cell membrane. Male trees accumulated a higher U concentration in their roots than female trees, whereas the transportation of U from roots to leaves in male trees was lower than that in female trees. Therefore, our results suggested that male trees have a higher tolerance capacity and greater ability to remediate U-polluted soil than female trees. Future phytoremediation studies should consider the differences between plant sexes in the tolerance to U-contaminated land.

The Influence of Climate Warming and Humidity on Plant Diversity and Soil Bacteria and Fungi Diversity in Desert Grassland

Our study, which was conducted in the desert grassland of Ningxia in China (E 107.285, N 37.763), involved an experiment with five levels of annual precipitation 33% (R33), 66% (R66), 100% (CK), 133% (R133), 166% (R166) and two temperature levels (inside Open-Top Chamber (OTC) and outside OTC). Our objective was to determine how plant, soil bacteria, and fungi diversity respond to climate change. Our study suggested that plant α-diversity in CK and TCK were significantly higher than that of other treatments. Increased precipitation promoted root biomass (RB) growth more than aboveground living biomass (ALB). R166 promoted the biomass of Agropyron mongolicum the most. In the fungi communities, temperature and precipitation interaction promoted α-diversity. In the fungi communities, the combination of increased temperature and natural precipitation (TCK) promoted β-diversity the most, whose distance was determined to be 25,124 according to PCA. In the bacteria communities, β-diversity in CK was significantly higher than in other treatments, and the distance was determined to be 3010 according to PCA. Soil bacteria and fungi α- and β-diversity, and ALB promoted plant diversity the most. The interactive effects of temperature and precipitation on C, N, and P contents of plants were larger than their independent effects.