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Glyphosate is a systemic non-selective herbicide, the most widely used in the world. Alongside with its use in agricultural and forestry systems, this herbicide is used in grasslands in late summer with the aim of promoting winter species with the consequent increase in stocking rate. However, its effects on non-target organisms, such as arbuscular mycorrhizal fungi (AMF), are unclear. Arbuscular mycorrhizal fungi (AMF) colonize the root of more than 80% of terrestrial plants, improving their growth and survival, and therefore playing a key role in ecosystem structure and function. The aim of this work was to investigate the possible pathways through which glyphosate application affects AMF spores viability and root colonization in grassland communities. Our hypothesis is that glyphosate application can damage AMF directly (through contact with spores and external hyphae) or indirectly through the changes it generates on host plants. The experiment had a factorial array with three factors: (1) plant species, at two levels (Paspalum dilatatum and Lotus tenuis), (2) doses of glyphosate, at three levels (0 l ha−1, 0.8 l ha−1 and 3 l ha −1), and (3) application site, at two levels: soil (direct pathway) and plant foliage (indirect pathway). Spore viability was reduced even under the lowest glyphosate rate, but only when it was applied on the soil. Total root colonization for both species was similarly decreased when glyphosate was applied to plant foliage or on soil, with no difference between 0.8 and 3 l ha−1. The number of arbuscules was 20% lower when glyphosate was applied on plant foliage, than when it was applied on the soil. Our findings illustrate that glyphosate application negatively affects AMF functionality in grasslands, due to different causes depending on the herbicide application site. While, under field conditions, the occurrence of direct and/or indirect pathways will depend on the plant cover at the time of glyphosate application, the consequences of this practice on the plant community structure will vary with the mycorrhizal dependence of the species composition regardless of the pathway involved. 相似文献
63.
Raymond W. Arritt Craig A. Clark A. Susana Goggi Higinio Lopez Sanchez Mark E. Westgate Jenny M. Riese 《Field Crops Research》2007
A three-dimensional Lagrangian random flight model was constructed for numerical simulations of maize pollen dispersion. The model simulates the paths of tracer particles which are interpreted as individual pollen grains, with particle motion determined by the mean flow and a stochastic turbulent velocity. The Lagrangian approach was chosen because it can be extended to complex flow regimes. The capacity of the model to simulate measured patterns of pollen deposition was tested by comparing simulations to measurements for a small maize canopy isolated within a large field of soybeans near Ames, Iowa, USA in August 2003. For this application, measurements from a single point meteorological observation were used to generate a surface layer wind profile over the maize canopy and surrounding soybean field. The method used to construct the wind field included development of internal boundary layers as the airflow passed from one canopy surface to another. The dispersion model produced spatial patterns of particle deposition that included the sharp near-source deposition gradient consistent with observations. The model tended to over-predict particle deposition near the source field and under-predict deposition at greater distances. Inclusion of the effect of the roughness difference between the maize canopy and the surrounding soybean canopy on the flow field was found to be essential for simulation accuracy. Agreement with observations improved considerably by including an approximation for vertical motions induced by changes in surface cover. These results indicate that the Lagrangian random flight model provides a realistic simulation of pollen dispersal from an isolated maize canopy. A more complete hydrodynamic model should be explored to better represent the influence of surface inhomogeneities on winds and turbulence. 相似文献
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海洋微塑料污染问题是全球研究热点,现有研究表明微塑料在海洋环境中无处不在,对海洋生态的威胁逐渐加重,伴随着海洋食品的兴起,人们也越来越重视微塑料污染对人体健康的危害。本文通过对海洋生物体内微塑料污染情况的概述,系统分析了微塑料对海洋生物造成的影响。主要针对微塑料检测的前处理方法以及组分的鉴定方法展开综述,对不同方法的优缺点进行比较,指出在微塑料检测研究中多种方法综合应用效果最佳。基于现阶段海洋微塑料的研究状况,从科学研究和管控方面讨论了目前研究中存在的问题,展望了未来的研究方向。 相似文献
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Marine organisms have been shown to be a valuable source for biologically active compounds for the prevention and treatment of cancer, inflammation, immune system diseases, and other pathologies. The advantage of studying organisms collected in the marine environment lies in their great biodiversity and in the variety of chemical structures of marine natural products. Various studies have focused on marine organism compounds with potential pharmaceutical applications, for instance, as immunomodulators, to treat cancer and immune-mediated diseases. Modulation of the immune system is defined as any change in the immune response that can result in the induction, expression, amplification, or inhibition of any phase of the immune response. Studies very often focus on the effects of marine-derived compounds on macrophages, as well as lymphocytes, by analyzing the release of mediators (cytokines) by using the immunological assay enzyme-linked immunosorbent assay (ELISA), Western blot, immunofluorescence, and real-time PCR. The main sources are fungi, bacteria, microalgae, macroalgae, sponges, mollusks, corals, and fishes. This review is focused on the marine-derived molecules discovered in the last three years as potential immunomodulatory drugs. 相似文献
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海晏牧场草地畜牧业最适载畜量的研究 总被引:6,自引:3,他引:3
根据青海省海晏牧场的草地资源,畜牧业生产特点,对草地畜牧业最适载畜量进行了研究。结果表明,不同放牧强度对夏秋草地和冬春草地地上生物量均有不同程度的影响,试验组与对照组对比,A、B两组生物量分别下降了25.66%,20.51%,而C、D、E组分别提高了26.39%,29.44%,33.84%,同时,放牧强度影响草地植被成分和牧草干物质的消化率,由此得出,在不影响草地和家畜生产的前提下,海晏牧场夏秋草 相似文献
70.
本文综述了水生光合生物无机碳的运输。作为光合作用的无机碳源CO2和HCO3-是水生光合生物最好的运输形式。但是,不同类型的水生光合生物无机碳的运输形式及其运输机理各不相同。 相似文献