In this study, genome-wide expression profiling based on Affymetrix ATH1 arrays was used to identify discriminating responses of Arabidopsis thaliana to five herbicides, which contain active ingredients targeting two different branches of amino acid biosynthesis. One herbicide contained glyphosate, which targets 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS), while the other four herbicides contain different acetolactate synthase (ALS) inhibiting compounds. In contrast to the herbicide containing glyphosate, which affected only a few transcripts, many effects of the ALS inhibiting herbicides were revealed based on transcriptional changes related to ribosome biogenesis and translation, secondary metabolism, cell wall modification and growth. The expression pattern of a set of 101 genes provided a specific, composite signature that was distinct from other major stress responses and differentiated among herbicides targeting the same enzyme (ALS) or containing the same chemical class of active ingredient (sulfonylurea). A set of homologous genes could be identified in Brassica napus that exhibited a similar expression pattern and correctly distinguished exposure to the five herbicides. Our results show the ability of a limited number of genes to classify and differentiate responses to closely related herbicides in A. thaliana and B. napus and the transferability of a complex transcriptional signature across species.Electronic supplementary materialThe online version of this article (doi:10.1007/s11103-009-9590-y) contains supplementary material, which is available to authorized users.

The Kenaga nomogram is a simple device that was developed by the U.S. Environmental Protection Agency (EPA) in the early 1980s and is currently used to predict the maximum potential pesticide residue levels in the food chain of wildlife before pesticide registration. To evaluate the accuracy of this nomogram, predicted levels were compared to levels reported in the literature. Data (obtained from the UTAB database developed by the University of Oklahoma) demonstrated that day‐0 levels predicted by the nomogram were often exceeded. Data from the UTAB database exceeded the nomogram predictions by the following percentages listed by crop: short range grass, 0; leafy crops, 3; long grass, 4; pods/seeds, 8; fruits, 19; and forage (legumes), 22. Minor modification of the nomogram is recommended. Recommended modifications would result in an elevation of the predicted residue levels for fruits and forage (legume) crops.

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The influence of low application rates of chlorsulfuron on the growth and reproduction of four taxonomically diverse plant species (canola, smartweed, soybean, and sunflower) were examined. Exposures examined ranged from 1 ϫ 10 Ϫ3 to 8 ϫ 10 Ϫ3 of the recommended field rates for cereal crops and were approximately 1,000 times less than the highest exposure recommended by the U.S. Environmental Protection Agency. Each species received a single application at one of three different stages of reproductive development. Effects were determined by measuring the height and yield of mature plants. The comparative effects of four different herbicides (atrazine, chlorsulfuron, glyphosate, and 2,4-D) were determined in the same manner by exposing each test species to a single low dose at one of three critical stages of reproductive development.Chlorsulfuron reduced the yield of all plants tested, with the amount of reduction depending on the time and rate of application. Most noteworthy was its influence on canola and soybean, in which at critical stages in development, applications of 9.2 ϫ 10 Ϫ5 and 1.8 ϫ 10 Ϫ4 kg/ha, respectively, reduced seed yields (dry wt) to 8 and 1% of those of controls without causing a significant change in vegetative growth. These low application rates are within the range of reported herbicide drift levels and suggest that chlorsulfuron may cause severe reduction in the yields of some nontarget crops if they are subjected to exposure at critical stages of development. Application of other herbicides at comparable rates and stages of plant development had no influence on either canola or soybean. Keywords-AtrazineChlorsulfuron Glyphosate 2,4-D Reproductive yieldEnviron. Toxicol. Chem. 15, 1996 J.S. Fletcher et al.

The influence of transpiration rate on the uptake and translocation of two industrial waste compounds, phenol and nitrobenzene, and one pesticide, 5-bromo-3-sec-butyl-6-methyluracil (bromacil), was examined. Carbon-14 moieties of each compound were provided separately in hydroponic solution to mature soybean plants [Glycine max (L.) Merr. dwarf cultivar Fiskeby vl maintained under three humidity conditions. The uptake of each compound was determined by monitoring the removal of 14C from the hydroponic solution. The extent to which was adsorbed to roots and translocated to plant shoots and leaves was examined by assaying root and shoot parts for ~4C. Bromacil was taken up slower than the other chemicals, had the most 14C translocated to the shoot, and the amount translocated to the shoot responded directly to the rate of transpiration. In contrast, both phenol and nitrobenzene were rapidly lost from solution and bound to the roots. Less than 1.$% of the '4C from phenol or nitrobenzene was translocated to the plant shoots. Increased transpiration rates had little influence on root binding of 1~C; however, increasing transpiration rate from low to medium was associated with an increased uptake of nitrobenzene. The three chemicals studied have similar Log Kow values, but their interactions with soybean were not the same. Thus, despite the usefulness of the octanol/water partitioning coefficient.in predicting the fate of organic chemicals in animals and in correlating with root binding and plant uptake for many pesticides, log Kow may not be equally useful in describing uptake and binding of nonpesticide chemicals in plants.Additional index words: Organic chemical uptake, Plant uptake, Glycine max (L.) Merr., Partitioning coefficient of octanol/water.