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Background Eragrostis plana is the main invasive plant in the Pampa Biome of southern Brazil. This plant is highly competitive, tolerant to abiotic stresses, and very difficult to manage. Plants exposed to abiotic stresses and herbicides develop mechanisms that help alleviate or reduce damage caused by stressors and transmit this ability to the progenies. Objective The study’s objectives were to ascertain whether acclimatization to stress due to drought and sub-lethal doses of glyphosate may decrease plant sensitivity to glyphosate and investigate the possible memory mechanisms involved in this process. Methods A population of E. plana was submitted to drought, glyphosate, or a combination of drought plus glyphosate for two generations. The progenies were analyzed for sensitivity to the herbicide glyphosate and for biochemical, metabolites, and molecular responses. Results When testing sensitivity to glyphosate in the G 2 generations, the DRYxGLY (plants stressed with drought plus glyphosate) was the least sensitive (ED50 443.0 g a.e. ha-1), while CHK (without stresses) was the most sensitive (ED50 278.0 g a.e. ha-1). Evaluating the effects of glyphosate, the CHK population showed a greater accumulation of oxidative damage and shikimic acid. While DRYxGLY had greater antioxidant activity and higher expressions of the EPSPS and ABC-carrier MRP10 genes. Conclusions Recurrent selection with drought stress and sub-lethal rate of glyphosate (DRYxGLY) showed reduced sensitivity to glyphosate in the second generation ( G 2 ). The conjunction of factors, including the upregulation of EPSPS and the ABC MRP10 transporter, antioxidant enzymes seem to decrease the sensitivity of the DRYxGLY population to glyphosate.

The phytostimulation is a phytoremediation technique that can be used to remediate area contaminated with herbicides. It is necessary to select plants with high capacity to stimulate soil microbial activity. The present work aimed at evaluating seven plant species regarding their ability to phytostimulate soil and enhance the degradation of the herbicides imazethapyr, imazapic and imazapyr in a lowland soil. An Alfisol Albaqualf was cultivated with the following species

Weedy rice (Oryza sativa L.) is widely recognized as a major constraint in cultivated rice systems globally. Seed shattering is related to the invasiveness and persistence of weedy ecotypes in field and exacerbates its control in cultivated rice systems. Shattering traits are controlled genetically and by different environmental conditions. At present, a rapidly changing environment, including rising levels of carbon dioxide [CO2], could alter shattering frequency, with subsequent effects on weed seed input and competition. The objective of the current study was to evaluate the interaction between weedy rice seed shattering and the transcriptional seed shattering-regulation genes as affected by weedy rice genotypes and atmospheric CO2 concentrations. We examined seven biotypes and two atmospheric CO2 concentrations: ambient {a[CO2]} and enhanced {e[CO2]} concentration, 400 and 700 µmol mol-1 respectively. Our results indicate that e[CO2] increases weedy rice seed shattering. The gene expression analysis demonstrates an effect of [CO2] in the expression of all gene shattering-related genes (OsCPL1, qSH1, Sh4, SHAT1, OsXTH8, OSH15, and SH5), with high variability observed between genotypes. Here we showed that increased CO2 concentration affects greatly seed shattering in weedy rice and in minor effect cultivated rice, by modulation of seed shattering-related genes and weedy genotypes showed the highest upregulation level of this genes. Thus, increased CO2 concentration positively affect panicle number and grain yield mainly in cultivated rice.

The aim of the present study was to assess the relative competition between white clover (cv. BRS URS Entrevero) and weed species Silene gallica L. through replacement series. The experiments followed a completely randomized design with four replications. The first study showed that the shoot dry mass of both species (white clover and S. gallica) became constant with 16 plants.pot-1 or 400 plants.m-2. In 2017, a study was conducted and it was repeated in 2018 in order to assess white clover competition with S. gallica under different crop: weed proportions pot-1 (100:00; 75:25; 50:50; 25:75 and 00:100). Competitiveness analysis was carried out through diagrams applied to replace experiments and through the relative competition indices. Morphological parameters such as plant height, leaf area and shoot dry mass of the crop and the weed were measured when S. gallica plants bloomed (105 days after species emergence). Results have proven the phenotypic plasticity of temperate-climate foragers such as white clover. This outcome shows that the competitive relationship with Silene gallica changes due to plant proportions composing the association. Therefore, it was possible to conclude that the species show similar competitive ability.

(1) Background: Elevated atmospheric CO2 concentration affects the growth and development of the rice crop. In Southern Brazil, rice is traditionally produced with continuous irrigation, implying a significant amount of water used. Besides, continuous flooding favors the uptake of toxic elements such as arsenic (As) and cadmium (Cd). In this work, one Brazilian rice cultivar (IRGA 424) was tested for the effects of elevated CO2 concentration and different water regimes on rice yield, and As and Cd accumulation in grain. (2) Methods: Rice was grown in two CO2 concentrations (400 and 700 µmol mol−1) and two irrigation regimes (continuous and intermittent). It was evaluated the number of tillers, plant height, aboveground dry weight (ADW), water use efficiency (WUE), rice yield components, and As and Cd concentration in rice grain. (3) Results: Rice plants were taller and had a higher WUE when cultivated at e[CO2]. The ADW and the rice yield component were not affected by CO2 levels nor water regimes. Intermittent flood regimes had a lower average As concentration. The Cd concentration in the samples in both growing seasons and all treatments was below the limit of quantitation (8.76 μg kg−1). (4) Conclusions: Enhanced CO2 concentration did not affect rice yield, increased the WUE, and reduced As concentration in grains. Regarding water management, the intermittent regime enhanced WUE and promoted a reduction in As concentration in grains.

In Brazil, hairy fleabane stands out among the main weeds of soybean crops, due to its aggressiveness and resistance to glyphosate. Thus, to avoid the selection of resistant populations to the glyphosate herbicide, the use of other herbicides has become critical to the management of this weed. This study aimed to evaluate the control efficiency of glyphosate and saflufenacil herbicides in hairy fleabane plants ( Conyza bonariensis ), as well as the type of interaction of the combination of those herbicides for controlling glyphosate-resistant hairy fleabane. A randomized blocks design, with four replications, was used. Treatments consisted of glyphosate doses (0 g ha -1 ; 270 g ha -1 ; 540 g ha -1 ; 1,080 g ha -1 ; 2,160 g ha -1 ; 4,320 g ha -1 ; 8,640 g ha -1 ; 17,280 g ha -1 ) combined with saflufenacil (0 g ha -1 ; 0.55 g ha -1 ; 1.09 g ha -1 ; 2.18 g ha -1 ; 4.37 g ha -1 ; 8.75 g ha -1 ; 17.5 g ha -1 ; 35 g ha -1 ), making six dose-response curves. A synergistic effect was observed between the glyphosate and saflufenacil herbicides for controlling the glyphosate-resistant hairy fleabane, being the mixture considered efficient for the biotype studied. Furthermore, the addition of glyphosate (540 g ha -1 ) to the saflufenacil herbicide (35 g ha -1 ) prevented the occurrence of regrowth and the dispersion of new hairy fleabane seeds, what does not occur in plants treated exclusively with saflufenacil.