Plant growth-promoting bacteria (PGPB) are found in plant tissues and promote plant growth by secretion of hormones and enzymes, or by facilitating the nutrient uptake. This study assessed forty PGPB isolates to determine their effects on maize and sorghum growth. These isolates were also compared with uninoculated plants, as negative (-N; without N fertilization) and positive (+N; with N fertilization) controls. Plant height, stem diameter, shoot and root dry mass, leaf N accumulation and chlorophyll content were evaluated. For both the maize and sorghum, the height, stem diameter and shoot dry mass in plants inoculated with PGPB were similar to those of uninoculated plants supplied with N, and the responses for root mass were higher than in plants supplied with N. However, the PGPB isolates did not promote N accumulation and chlorophyll content similar to those of uninoculated plants supplied with N. The IPACC26 and IPACC30 isolates, both identified as Bacillus subtilis, resulted in better responses for plant growth and N accumulation than the other isolates.

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In 1980, thousands of metalworkers from the region of greater São Paulo known as the ''ABC'' region carried out one of the most intense and lasting strikes in the history of the Brazilian working class. For forty-one days, striking workers resisted the repression that bosses and the nation's military regime mounted against them, which contributed to the collective worker mobilization that spread throughout the spaces of the city -especially the streets of the São Bernardo do Campo neighborhood. Expelled from factories and major public spaces, workers were able to maintain the strike mainly in the neighborhoods where they lived, thus politicizing the spaces and relationships of their daily lives and redefining the geography of collective mobilization. This article analyzes aspects of this process, highlighting the importance of workers' social networks to the notable (re)appropriation of urban space that characterized the strike movement.

RESUMOEste artigo analisa o papel dos piquetes em duas das mais importantes greves da história brasileira, a "greve dos 400 mil", que envolveu diversas categorias industriais em São Paulo e cidades vizinhas em 1957, e a "greve dos 41 dias", em 1980, organizada pelos metalúrgicos do ABC Paulista, na região metropolitana da cidade de São Paulo. Embora separadas no tempo em quase 25 anos, essas duas grandes paralisações se tornaram exemplos paradigmáticos das formas de ação sindical, tanto do sindicalismo sustentado pelo bloco formado pelas forças "nacional-reformistas" e comunistas, hegemônicas no período anterior ao golpe civil-militar de 1964, quanto do "novo sindicalismo" que emergiu a partir do final dos anos 1970. A análise mais detida das greves mostra elementos destacados de aproximação e semelhanças entre os dois movimentos. A análise mais apurada da ação dos piquetes indica um repertório organizativo mais permanente e resistente do que indicado pela bibliografia especializada e pelo discurso das lideranças políticas e sindicais. Palavras-chave: greves; piquetes; trabalhadores; sindicalismo. ABSTRACT This article analyzes the role of pickets in two of the most emblematic strikes in Brazilian labor history: the "strike of the 400,000," which involved several industry sectors in São Paulo and neighboring cities in 1957, and the 1980 "forty-one days strike," involving the metalworkers of the ABC Paulista, in the metropolitan area of the city of São Paulo. Both strikes broke out at a time of profound reconfiguration of Brazilian society, marked by the processes of industrialization, migration, and urbanization. Although separated by a time Artigo recebido em 4 de maio de 2016 e aprovado para publicação em 5 de dezembro de 2016.

The aim of this study was to evaluate, in the field, the soilrespiration and bulk density underconventional and organic farming plots. The evaluations were made in different plots established as conventional farming system and organic farming system with six, nine, twelve, fifteen, eighteen and twenty one months old. Plots were divided in four transects (subplots) and ineach subplot were evaluated soil respiration, bulk density and porosity. The soil respiration was significantly greater in organic farming system with fifteen, eighteen and twenty-one monthsold as compared with conventional farming. Soil bulk density decreased fifteen months afteradoption of organic system. Theresults showed that the adoption of practices in organic farming plots increases microbial activity and decreases soil bulk density over time.