| Herbicides are indispensable for modern agriculture in most of countries. However, the intensive agriculture over the last decades has led to dramatically elevated releases of herbicides into arable soils. Due to their massive emission into environments, toxic herbicides have become global environmental problems. Recent studies have shown that herbicides applied to soils are frequently detected as pollutants in lakes, rivers, coastal marine waters and even underground waters. The mobility of herbicides into groundwater via soil media has become one of the primary approaches leading to the widespread pollution to ecosystems. Although they are designed to kill weeds through specific mechanisms, herbicides are not specific to their targets. Moreover, when practically used, herbicides are also accumulated in soils or where crops are growing. Herbicides accumulated by crops not only exert detrimental effects on crop itself, but also are very harmful to ecosystems. Contamination with herbicides not only affects the quality of crops which directly accumulate herbicides, but also serves as a food chain threatening human health. As herbicides are readily uptaken by crops, overload of herbicides into crop tissues is most likely to disrupt many biological processes. Thus, it is very important to dissect mobility, toxicological and adaptive response to herbicides.The sorption-desorption and mobility of propachlor was investigated in three cultivated soils:collected from Nanjing (NJ)(32°10’N,118°45’E.), Tongren (TR)(27°43’ N,109°11’E.) and Yiwu (YW)(29°18’N,120°4’E.) in China. The effects of two type solid organic matters were also studied. Two sorts of solid organic matters were air-dried lakebed sludge (SL) and pig manure compost (PMC). In this study, sorption equilibrium studies were conducted for all the three soils. The equilibrium time of propachlor in NJ, TR and YW soil-water (1/5, w/v) were7,15and11h at25±1℃, respectively. Batch equilibrium experiment was conducted to evaluate the effect of two types of solid organic matters on the sorption-desorption behavior of propachlor in the soils. Our analysis showed that the sorption-desorption data fitted the Freundlich equation, and that sorption capacity in soils for propachlor by application of PMC was promoted more than SL, but desorption capacity of propachlor by SL treatment was largest. We also tested the mobility of propachlor in packed soil columns and soil plate. The results indicated that addition of solid organic matters to three soils influenced significantly the mobility of propachlor.Atrazine is widely used for controlling grass weeds for cereal production. However, overuse of the herbicide resulted in frequent occurrence of contamination in soils. To assess atrazine-induced toxicity in rice, we investigated the physiological response of rice to the herbicide. Rice seedings were cultured in the nutrient solution with atrazine at concentrations of0-0.8mg L-1. Treatment with atrazine induced the accumulation of reactive oxygen species (ROS) in plants and triggered the peroxidation of plasma membrane lipids, programmed cell death (PCD) in the plant. To understand the biochemical responses to the herbicide, activities of the antioxidant enzymes, such as superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), ascorbate peroxidase (APX), glutathione reductase (GR) and glutathione S-transferase (GST) were assayed. We also assayed genes expression of GST, APX, GR and HO-1by semi-quantitative RT-PCR. Under the atrazine exposure, the SOD, POD, CAT, APX, GR activities were increased. Also, expression of GST-3,4, APX-2,3, GR-1,3and HO-1were upregulated or downregulated.The toxicological processes of atrazine in food crops and human beings are not fully understood. High-throughput sequencing of atrazine-exposed rice (Oryza sativa) were performed to analyze global expression and complexity of genes in the crop. Four libraries were constructed from shoots and roots with or without atrazine exposure. We sequenced5,375,999-6,039,618clean tags that corresponded to111,301-248,802distinct tags for Root-Atr., Shoot-Atr., Root+Atr. and Shoot+Atr. libraries, respectively. Mapping the clean tags to gene databases generated18,833-21,007annotated genes for each library. Most of annotated genes were differentially expressed among the libraries. The most40differentially expressed genes were associated with resistance to environmental stress, degradation of xenobiotics and molecule metabolism. Validation of genes by quantitative RT-PCR confirmed the deep-sequencing results. The transcriptome sequences were further subjected to Gene Orthology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis and showed modified molecular functions and metabolic pathways. Results not only demonstrate transcriptional complexity in rice with atrazine but also represent a major improvement for analyzing transcriptional changes on a large scale in xenobiotics-responsive toxicology.Finally, the accumulation of atrazine in rice seedlings were determined. The plants were cultured in the nutrient solution with atrazine at concentrations of0.05-0.8mg L-1. Accumulation of atrazine in rice seedings was positively correlated with the external atrazine concentrations, but negatively with the plant growth. In shoots, the value of bioconcentration factors (BCFs) higher than root, and the value of translocation factors (TFs) were negative correlated with the external atrazine concentrations. |
PDF Full Text Request