Effects of six selected antibiotics on plant growth and soil microbial and enzymatic activities

Large-scale use of the persistent and potent neonicotinoid and fipronil insecticides has raised concerns about risks to ecosystem functions provided by a wide range of species and environments affected by these insecticides. The concept of ecosystem services is widely used in decision making in the context of valuing the service potentials, benefits, and use values that well-functioning ecosystems provide to humans and the biosphere and, as an endpoint (value to be protected), in ecological risk assessment of chemicals. Neonicotinoid insecticides are frequently detected in soil and water and are also found in air, as dust particles during sowing of crops and aerosols during spraying. These environmental media provide essential resources to support biodiversity, but are known to be threatened by long-term or repeated contamination by neonicotinoids and fipronil. We review the state of knowledge regarding the potential impacts of these insecticides on ecosystem functioning and services provided by terrestrial and aquatic ecosystems including soil and freshwater functions, fisheries, biological pest control, and pollination services. Empirical studies examining the specific impacts of neonicotinoids and fipronil to ecosystem services have focused largely on the negative impacts to beneficial insect species (honeybees) and the impact on pollination service of food crops. However, here we document broader evidence of the effects on ecosystem functions regulating soil and water quality, pest control, pollination, ecosystem resilience, and community diversity. In particular, microbes, invertebrates, and fish play critical roles as decomposers, pollinators, consumers, and predators, which collectively maintain healthy communities and ecosystem integrity. Several examples in this review demonstrate evidence of the negative impacts of systemic insecticides on decomposition, nutrient cycling, soil respiration, and invertebrate populations valued by humans. Invertebrates, particularly earthworms that are important for soil processes, wild and domestic insect pollinators which are important for plant and crop production, and several freshwater taxa which are involved in aquatic nutrient cycling, were all found to be highly susceptible to lethal and sublethal effects of neonicotinoids and/or fipronil at environmentally relevant concentrations. By contrast, most microbes and fish do not appear to be as sensitive under normal exposure scenarios, though the effects on fish may be important in certain realms such as combined fish-rice farming systems and through food chain effects. We highlight the economic and cultural concerns around agriculture and aquaculture production and the role these insecticides may have in threatening food security. Overall, we recommend improved sustainable agricultural practices that restrict systemic insecticide use to maintain and support several ecosystem services that humans fundamentally depend on.

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Risks of large-scale use of systemic insecticides to ecosystem functioning and services

Pesticides are extensively used in agriculture as a part of pest control strategies. Owing to their xenobiotics characteristics, pesticides may adversely affect the proliferation of beneficial soil microorganisms and their associated biotransformation in the soil. Inactivation of nitrogen‐fixing and phosphorus‐solubilizing microorganisms is observed in pesticide‐contaminated soils. Recent studies show that some pesticides disturb molecular interactions between plants and N‐fixing rhizobacteria and consequently inhibit the vital process of biological nitrogen fixation. Similarly, many studies show that pesticides reduce activities of soil enzymes that are key indicators of soil health. The applied pesticides may also influence many biochemical reactions such as mineralization of organic matter, nitrification, denitrification, ammonification, redox reactions, methanogenesis, etc. However, a few reports reveal some positive effects of applied pesticides on soil health. In this chapter, we attempt to analyze the impacts of pesticides on soil microbial communities, soil biochemical reactions, and soil enzymes.

Chapter 5: Impact of pesticides on soil microbial diversity, enzymes, and biochemical reactions.

The effects of middle term (7 years) consistent tillage practices on the catalase (CAT), urease (URE) and invertase (INV) activities were investigated during the whole winter wheat growing period on a loess soil in Luoyang (east edge of the Chinese Loess Plateau, Henan province, China). Field plots, set up in 1999, included following tillage practices: subsoiling with mulch (SS), no-till with mulch (NT), reduced tillage (RT), and a conventional control (CT). A clear redistribution of soil organic carbon (SOC) and total nitrogen (TN) was found along the slope in RT and CT, however, no difference was observed between studied enzyme activities along different slope positions. SS had higher winter wheat yield than other treatments, which was attributed to the increased soil water content and improvement of soil fertility. Changes in soil temperature and soil moisture content influenced the magnitude of the enzyme activities, but not the ranking of the different treatments during most of the season. SS consistently had higher enzyme activities compared to other treatments. This indicated that seasonal fluctuations did not obscure effects associated with soil tillage practices and enzyme activities could reflect the effects of conversion of soil tillage practices on soil quality. Time within the growing season had a clear impact upon the enzyme activities. Comparatively higher enzyme activities were observed in the stages with vigorous vegetative growth of winter wheat than in stages with productive growth.

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Changes of soil enzyme activities under different tillage practices in the Chinese Loess Plateau

The use of pesticides in agriculture has highly increased during the last 40 years to increase crop yields. However, today most pesticides are polluting water, soil, atmosphere and food. Pesticides are also impact soil enzymes, which are essential catalysts ruling the quality of soil life. In particular, the activity of soil enzymes control nutrient cycles, and, in turn, fertilization. Here, we review the effects of pesticides on the activity of soil enzymes in terrestrial ecosystems. Enzymes include dehydrogenase, fluorescein diacetate hydrolase, acid phosphatase, alkaline phosphatase, phosphatase, β-glucosidase, cellulase, urease and aryl-sulfatase. Those enzymes are involved in the cycles of carbon, nitrogen, sulfur and phosphorus. The main points of our analysis are (1) the common inhibition of dehydrogenase in 61 % of studies, stimulation of cellulase in 56 % of studies and no response of aryl-sulfatase in 67 % of studies. (2) Fungicides have mainly negative effects on enzymatic activities. (3) Insecticides can be classified into two groups, the first group represented by endosulfan having an overall positive impact while the second group having a negative effect. (4) Herbicides can be classified into two groups, one group with few positive effect and another group with negative effect.

Effects of pesticides on soil enzymes: a review

Influence of acetamiprid on soil enzymatic activities and respiration

The integrated impact of GDP growth, industrialization, energy use, and urbanization on CO2 emissions in developing countries: Evidence from the panel ARDL approach.

<p id="C3">To explore <italic>AGO</italic> genes related to leaf stripe in Tibetan hulless barley (BLS), we obtained a differentially expressed <italic>HvMEL1 AGO </italic>gene from the transcriptional sequencing in normal and diseased leaves from resistant Tibetan hulless barley variety Kunlun 14 and the susceptible variety 1141. The <italic>HvMEL1 AGO</italic> gene was 3462 bp in length, of which the CDS (coding domain sequence) was 100% consistent in Kunlun 14 and 1141 varieties. The length of <italic>HvMEL1 AGO</italic> gene was 3161 bp without intron, contained a 3129 bp open reading frame, encoded 1043 amino acids, had a theoretical isoelectric point of 9.33, and has a predicted molecular weight of 115,865.58 Da. Protein sequence analysis showed that HvMEL1 AGO was a hydrophilic unstable acidic protein with highly conserved structural domains of DUF1785, PAZ and PIWI, belonging to <italic>AGO</italic> gene family. Phylogenetic tree analysis showed that HvMEL1 AGO belonged to the AGO1 class in <italic>Arabidopsis</italic> AGO family phylogenetic tree with HvAGO12, HvAGO18, HvAGO1D and HvAGO1B in barley AGO family, and were closely related to HvAGO12. The predicted protein interactions showed that the known proteins that acted closely with MEL1 in rice were the DCL classes, DCL1, DCL2A, DCL3A, DCL3B and DCL4, respectively. Semi-quantitative and quantitative PCR results indicated that the relative expression levels of <italic>HvMEL1 AGO</italic> gene were significantly down-regulated in 1141 and Kunlun 14 under BLS. We hypothesized that <italic>HvMEL1 AGO</italic> gene played an important role in the streak resistance mechanism of barley. This study lays the foundation for exploring the role and regulatory mechanism of <italic>HvMEL1 AGO</italic> in the process of BLS resistance. 

Isolation and expression of a new gene <italic>HvMEL1 AGO</italic> in Tibetan hulless barley under leaf stripe stress

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Xiao-hua Yao

Papers

Influence of acetamiprid on soil enzymatic activities and respiration

The integrated impact of GDP growth, industrialization, energy use, and urbanization on CO2 emissions in developing countries: Evidence from the panel ARDL approach.

Isolation and expression of a new gene <italic>HvMEL1 AGO</italic> in Tibetan hulless barley under leaf stripe stress

Effects of long-term cropping of tibetan barley (kunlun 14) on soil microbial diversity, enzymatic activities, and crop phenotypic quality