Abstract Background Among the weeds in Iran, resistant Lolium rigidum Gaud is considered a troublesome weed in winter cereals due to its tendency to evolve cross (CR) and multiple resistance (MR) to herbicides. Objective This research examined the patterns and mechanisms of L. rigidum resistance to clodinafop-propargyl (CP) and mesosulfuron methyl+iodosulfuron methyl (MI). Methods Experiments were conducted on four putative-resistant L. rigidum biotypes and one susceptible biotype. The dose-response assay was performed on the biotypes with CP and MI. CR and MR were investigated with haloxyfop-R-methyl (HRM), sethoxydim (SD), pinoxaden (PN). and isoproturon+ diflufenican (ID) herbicides. An indirect study of the metabolism of herbicides was carried out using the cytochrome P450 monooxygenase (CYP450) inhibitors 1-aminobenzotriazole (ABT), piperonyl butoxide (PBO) and malathion. Finally, sequencing of ALS and ACCase genes was performed to investigate target-site resistance. Results All putative-resistant L. rigidum biotypes were resistant to CP, MI, and HRM, but susceptible to SD, PN, and ID. The indirect study showed that the P450 enzyme had no role in the evolution of resistance in L. rigidum biotypes. Resistance in this species was due to Ile-1781-Leu and Pro-197-Ser substitutions on ACCase and ALS encoding genes led to resistance, respectively. Conclusions Resistance in the studied L. rigidum biotypes to ALS and ACCase inhibiting was due of target site resistance. If these resistant biotypes are not controlled, they will become a problem for farmers in the region.

Abstract Herbicide resistance in weeds is an evolutionary process. Although there is a great global diversity of weeds, independent origins of herbicide resistance evolution have been shown to converge into similar molecular and physiological resistance mechanisms in geographically distant weed populations. Amaranthus species have shown an extraordinary ability to evolve herbicide resistance and invade new environments at a global scale, which represents an opportunity for identifying adaptive evolutionary patterns. The most frequent cases of herbicide-resistant Amaranthus species have been identified in North America, where A. hybridus, A. palmeri, A. tuberculatus and A. retroflexus comprise more than 90% of them. Meanwhile, A. retroflexus, A. hybridus and A. palmeri have been the most reported species in South America. Around 70% of the cases of herbicide-resistant Amaranthus species have been identified in global soybean and corn crops. The higher fecundity and adaptability of plants to a broad range of environments would make populations more likely to persist and be selected for herbicide resistance. Co-evolution of multiple herbicide resistance mechanisms at the plant and/or population level is evident in weed species. For Amaranthus spp., resistance cases highlight evolutionary responses to herbicide use with clear patterns of selection for multiple herbicide resistance in particular regions and spread to new areas within and between global cropping systems. Seed-mediated gene flow is an important component to the spread of herbicide resistant Amaranthus spp. populations. Reduction of the intensity of herbicide selection by combining diverse and integrated weed control practices should be a common goal in weed management programs.

Resumo Estudos recentes na área do ensino de engenharia têm mostrado a importância de se desenvolver novas abordagens nas aulas de laboratório experimentais de física nas séries iniciais dos cursos de engenharia. Neste artigo apresentamos os resultados de uma proposta de desenvolvimento, baseada na metodologia PBL, de um experimento de fácil construção e montagem, porém de análise e interpretação dos dados bastante complexos. O experimento denominado, pêndulo a laser, tem o objetivo de analisar o movimento de um ponto de luz produzido por um laser que está acoplado num pêndulo de haste rígida cuja oscilação do ponto de luz ocorre sobre um plano inclinado de ângulo variável. Os dados experimentais foram obtidos por meio das filmagens com o uso do software de rastreamento Tracker®enquanto as análises dos modelos teóricos desse problema, bem como os gráficos e as curvas ajustadas foram obtidos com o uso do software de análise de dados GNU Octave®. Por fim, uma simulação em Python de todo o experimento foi construída a fim de auxiliar no processo de visualização e entendimento do problema analisado.

Abstract Recent studies in engineering education have shown the importance of developing new approaches in experimental physics lab in the initial series of engineering courses. In this paper it was analyzed the motion of a light spot produced by an oscillating laser on a rigid rod pendulum over a inclined plane. The main parameter in this paper is the distance between the light spot and the pendulum rotating axis. The study of this parameter was made by the analysis of its behavior with respect to time, which was accomplished by comparison of data obtained by two different methods: the analysis of filming of the experiment and the theoretical prevision aligned with the curves fitting over the experimental data. The empirical data were obtained from the video analysis using the Tracker ®software and the graphics and fitting curves were obtained with use of the data analysis software GNU Octave®. This experiment is simple and interesting as well as can be done with accessible resources. Finally, a Python simulation of the whole experiment was constructed in order to assist in the process of visualization and understanding of the analyzed problem.