草甘膦对叶绿体能量转换的影响

除草剂草甘膦抑制植物叶绿体光合磷酸化活力,促进希尔反应活力,表现出明显的解偶联效应。它对叶绿体膜上腺三磷酶(ATPase)活力也起抑制效应,说明ATP合成被抑制不是由ATP酶活力变化所引起。这种解偶联现象主要是因光下质子转移受到抑制,在较低浓度的草甘膦影响下,先抑制质醌转移的质子进入膜内腔,浓度增加到20 mM,对水释放质子也有抑制。所以草甘膦对叶绿体能量转换的影响主要反映在质子转移被抑制,引起磷酸化活力受抑制。     

Bioassays with a floating aquatic plant (Lemna minor) for effects of sprayed and dissolved glyphosate

Macrophytes in forested areas and in prairie wetlands furnish critical habitat for aquatic communities and for several species of birds and mammals. North American agriculture relies heavily on herbicides and these compounds are detected routinely in surface waters of Western Canada. The question is whether these residues have biological meaning. There is surprisingly little literature on the responses of macrophytes to herbicides, or indeed to other chemicals. Previously we have used common duckweed in efforts to detect effects of herbicides and other chemicals. Duckweed clones were developed from local collections and grown axenically. In this study the plants were exposed to glyphosate herbicide either by dissolving formulated Roundup^® (Monsanto Canada Inc.) in the culture media or by spraying of the cultures in a laboratory spray chamber. Plant growth was monitored by counting the fronds present on several occasions over a 2-week period following treatment and by taking wet and dry weights of plants after the final counting period. Plant growth, as measured by increased numbers of fronds or increased wet or dry weights was relatively insensitive to glyphosate dissolved in the culture medium. However, the plants were killed by application of glyphosate as a spray.     

Low concentrations of glyphosate‐based herbicide cause complete loss of sperm motility of yellowtail tetra fish Astyanax lacustris

Environmental relevant concentrations of glyphosate‐based herbicide as 50 µg l^?1, 300 µg l^?1 and 1800 µg l^?1 can affect sperm quality of yellowtail tetra fish Astyanax lacustris . Viability of sperm cells was impaired at 300 µg l^?1, a concentration that is within legal limits in U.S.A. waterbodies, while motility was impaired at 50 µg l^?1, which is the more stringent limit set in Brazilian law. Therefore, environment protection agencies must review regulations of glyphosate‐based herbicides on water bodies.     

Commercially formulated glyphosate can kill non‐target pollinator bees under laboratory conditions

The use of glyphosate‐based herbicides in agroecosystems has increased over the past few years because of the advent of genetically modified glyphosate‐resistant crops and resistant weeds. This is alarming because of potential damaging effects on non‐target organisms. In sub‐Saharan Africa, for example Ghana, many rural farmers have not received training in the use of glyphosate‐based herbicides, thus tend to apply higher than recommended concentrations on farms. Therefore, this study investigated the effect of glyphosate‐based herbicides on beneficial insects under laboratory conditions, using Apis mellifera L. (Hymenoptera: Apidae, Apini) and Hypotrigona ruspolii (Magretti) (Hymenoptera: Apidae, Meliponini) as models. The bees were put in contact for 24 h with the recommended concentration of Sunphosate 360 SL, a glyphosate‐based herbicide, 2× the recommended concentration, or distilled water as control. The effect of the herbicide on the bees was compared to the effect of a lambda‐cyhalothrin insecticide. Generally, more bees died after contact with plants freshly sprayed with the herbicide than on herbicide‐treated filter paper. In both cases, more bees died after contact with the higher concentration of the herbicide. These findings suggest that beneficial insects, specifically A. mellifera and H. ruspolii, may get killed if they are sprayed upon or come into contact with plants that have been freshly sprayed with (more than) the recommended concentration of glyphosate‐based herbicides. Therefore, it is important to restrict access and use of such herbicides to trained personnel who will comply with spraying guidelines, that is, recommended concentrations and timing of spray. Spraying at a time when insects are flying about may be detrimental to beneficial insects such as pollinator bees, parasitoids, and predators.     

Induction of glutathione S-transferase activity and glutathione level in plants exposed to glyphosate

Treatment with the herbicide glyphosate led to significantly increased activities of the enzyme gluiathione S-transferase (GST, EC 2.5.1.18) in wheat ( Triticum aestivum L. cv. Kadett and cv. Satu), pea ( Pisum sativum L. ev. Debreceni Világoszöld) and in maize ( Zea mays. L. Pioneer 3839 hybrid) tissues. GST activities in wheat seedlings (cv. Kadett) exposed to 960 μM glyphosate for 4 days were ca 6-fold and 3-fold higher in shoots and roots, respectively, than in the controls. Glyphosate increased the GST activity to a lesser extent in pea and maize than in wheat. In wheat seedlings (cv. Satu) exposed let 120 μM glyphosate gradual increases in the content of non-protein thiols were observed. After 7 days exposure to glyphosate the thiol levels rose to about 360% and 220% of the controls in wheal shoots and roots, respectively. The elevation of thiol content in glyphosate-treated plants was shown to be primarily due increases of glutathione level. These results suggest that the enhanced glutathione metabolism may have a role in the mode of action or degradation of this herbicide.     

Fitness costs of herbicide resistance across natural populations of the common morning glory,Ipomoea purpurea

Although fitness costs associated with plant defensive traits are widely expected, they are not universally detected, calling into question their generality. Here, we examine the potential for life‐history trade‐offs associated with herbicide resistance by examining seed germination, root growth, and above‐ground growth across 43 naturally occurring populations of Ipomoea purpurea that vary in their resistance to RoundUp ® , the most commonly used herbicide worldwide. We find evidence for life‐history trade‐offs associated with all three traits; highly resistant populations had lower germination, shorter roots, and smaller above‐ground size. A visual exploration of the data indicated that the type of trade‐off may differ among populations. Our results demonstrate that costs of adaptation may be present at stages other than simply the production of progeny in this agricultural weed. Additionally, the cumulative effect of costs at multiple life cycle stages can result in severe consequences to fitness when adapting to novel environments.     

Optimization of liquid-state fermentation conditions for the glyphosate degradation enzyme production of strain Aspergillus oryzae by ultraviolet mutagenesis

This study aimed to obtain strains with high glyphosate-degrading ability and improve the ability of glyphosate degradation enzyme by the optimization of fermentation conditions. Spore from Aspergillus oryzae A-F02 was subjected to ultraviolet mutagenesis. Single-factor experiment and response surface methodology were used to optimize glyphosate degradation enzyme production from mutant strain by liquid-state fermentation. Four mutant strains were obtained and named as FUJX 001, FUJX 002, FUJX 003, and FUJX 004, in which FUJX 001 gave the highest total enzyme activity. Starch concentration at 0.56%, GP concentration at 1,370?mg/l, initial pH at 6.8, and temperature at 30°C were the optimum conditions for the improved glyphosate degradation endoenzyme production of A. oryzae FUJX 001. Under these conditions, the experimental endoenzyme activity was 784.15?U/100?ml fermentation liquor. The result (784.15?U/100?ml fermentation liquor) was approximately 14-fold higher than that of the original strain. The result highlights the potential of glyphosate degradation enzyme to degrade glyphosate.     

Increasing the Effectiveness of Reed canary grass (Phalaris arundinacea L.) Control in Wet Meadow Restorations

Restoration practices are often based on trial and error or anecdotal information because data from controlled experiments are not available. In wet meadow restorations of the upper Midwest United States, Reed canary grass ( Phalaris arundinacea L.) is controlled with spring burning and spring glyphosate herbicide applications, but the relative effectiveness of either treatment with respect to P. arundinacea growth and life history has not been assessed. We designed a multiyear field experiment to evaluate effects of burning and herbicide application timings on P. arundinacea populations. Burning did not reduce P. arundinacea biomass but reduced the P. arundinacea seed bank, potentially limiting recolonization of P. arundinacea . Glyphosate applications in late August and late September were more effective than in mid-May (due to enhanced glyphosate translocation to rhizomes), such that two mid-May applications reduced P. arundinacea biomass to a level equivalent to that achieved by one late-season application. Phalaris. arundinacea recolonized rapidly from the seed bank and, in plots that received suboptimally timed (mid-May) herbicide, from rhizomes. Establishment of native species was very low, likely due to competition with recolonizing P. arundinacea . Unplanted species (from the seed bank and refugial populations) accounted for the majority of non- P. arundinacea biomass. Recolonization of other species was strongly limited by a threshold level of P. arundinacea biomass. Adequate site preparation (over multiple growing seasons) and aftercare (selective removal of P. arundinacea ) will be the key to facilitating subsequent wet meadow vegetation establishment. This research provides an example of the importance of experimental evidence as the basis to improve the efficiency of restoration practices.     

Changes in fitness-associated traits due to the stacking of transgenic glyphosate resistance and insect resistance in Brassica napus L

Increasingly, genetically modified crops are being developed to express multiple 'stacked' traits for different types of transgenes, for example, herbicide resistance, insect resistance, crop quality and tolerance to environmental stresses. The release of crops that express multiple traits could result in ecological changes in weedy environments if feral crop plants or hybrids formed with compatible weeds results in more competitive plants outside of agriculture. To examine the effects of combining transgenes, we developed a stacked line of canola (Brassica napus L.) from a segregating F(2) population that expresses both transgenic glyphosate resistance (CP4 EPSPS) and lepidopteran insect resistance (Cry1Ac). Fitness-associated traits were evaluated between this stacked genotype and five other Brassica genotypes in constructed mesocosm plant communities exposed to insect herbivores (Plutella xylostella L.) or glyphosate-drift. Vegetative biomass, seed production and relative fecundity were all reduced in stacked trait plants when compared with non-transgenic plants in control treatments, indicating potential costs of expressing multiple transgenes without selection pressure. Although costs of the transgenes were offset by selective treatment, the stacked genotype continued to produce fewer seeds than either single transgenic line. However, the increase in fitness of the stacked genotype under selective pressure contributed to an increased number of seeds within the mesocosm community carrying unselected, hitchhiking transgenes. These results demonstrate that the stacking of these transgenes in canola results in fitness costs and benefits that are dependent on the type and strength of selection pressure, and could also contribute to changes in plant communities through hitchhiking of unselected traits.