A survey in various countries revealed that the N2-fixing Spirillum lipoferum Beijerinck is a very common root and soil inhabitant in the tropics. More than half of the grass root and soil samples collected in tropical countries (four African countries and Brazil) contained abundant S. lipoferum populations, while less than 10% of the samples collected in temperate South Brazil, Kenya, and the U.S.A. contained the organism. There is a pronounced vegetation effect. Panicum maximum seems the most favorable among the forage grasses, while few positive samples were found under virgin tropical forest. Legume roots contained less S. lipoferum than adjacent soils. More than 80% of the samples from cereal roots (maize, sorghum, wheat, and rye) grown in fields fertilized with PK and Mo, in Rio de Janeiro State, were positive. Maize and sorghum grown under similar conditions in Wisconsin contained less than 10% of positive samples, but when maize fields were inoculated 90% of the root samples contained S. lipoferum. Alluvial soils were more favorable than eroded hill soils. Occurrence in soil was strongly pH-dependent with a pH around 7, being optimal (correlation coefficient r = 0.90). Sporadic occurrence was observed even in soils with pH 4.8. Surface-sterilized P. maximum roots collected from soils with pH ranging from 4.8 to 7.2 contained high S. lipoferum numbers which did not correlate with soil pH (r = 0.41). Amendment with malate of acid soils was not very effective in increasing nitrogenase (N2-ase) activity, but in two soils with pH above 6.4, high N2-ase activity was obtained after 16 to 48 h of incubation. In two soils from a temperate climate region, inoculation with S. lipoferum increased N2-ase activity produced through malate amendment.

Determination of bioindicators of auxinic herbicides residuesHerbicides that present soil residual activity may become a problem in agricultural crops due to the possibility of crops successors intoxication. It is hard to detect residues of hormonal herbicides using the bioassay technique, due to the variation in the growth response of the indicator plant. The objective of this work was to select plants and variables susceptible to the herbicides 2,4-D and picloram for soil residue indication..To make it possible, two bioassays were performed,, where each of them consisted of 60 treatments in a factorial scheme with the combination of three plant species (Lycopersicon esculentum, Cucumis sativus and Beta vulgaris), two substrates (sand and soil sample) and 10 subdoses of herbicide (0, 3, 6, 12, 22.5, 47, 94, 187.5, 375 and 750 g ha -1 ) and (0, 3, 6, 9, 18, 30, 60, 123; 246 and 501 Recebido para publicação em 29/12/2011 e aprovado em 07/03/2013.

The aim of this study was adapting the methodology of the accelerated aging test (AA) and electrical conductivity test (EC) to evaluate seed quality of crambe, as well as verifying enzymatic activity in relation to vigor differences. Crambe seed lots, cv. FMS Brilhante, were evaluated by the AA test, for periods of 0, 24, 48, 72 and 96 h, at 42 °C, with and without NaCl saturated solution; and the EC test, by soaking seeds into deionized water (mL) in the ratios of 25/25, 25/50, 50/50 and 50/75 (seed/water) for 2, 4, 6, 8, 10, 12, 14, 16 and 18 h. The electrophoretic profile for isozymes esterase, superoxide dismutase, catalase, isocitrate lyase, alcohol dehydrogenase and malate dehydrogenase was evaluated on polyacrylamide gel (7.5%). The AA test conducted at 42 °C, for 96 h, was efficient to detect differences on seed quality levels; however, the EC test was not suitable to evaluate vigor of those seeds. The bands stained for isozymes esterase, superoxide dismutase and catalase were evident for the more vigorous seeds; and the bands for isozymes isocitrate lyase and alcohol dehydrogenase were less evident for the less vigorous seeds. For enzyme malate dehydrogenase enzyme intensity of bands was similar.

ResumoObjetivou-se com a pesquisa avaliar a influência da aplicação do herbicida Diquat, em diferentes épocas, sobre a produção e qualidade fisiológica das sementes de feijão, cultivar Pérola. O delineamento experimental utilizado foi de blocos casualizados (DBC). Os tratamentos constituíram da aplicação do herbicida com dosagem de 400 g i.a./ha, em oito estádios de aplicação (83, 85, 87, 89, 91, 93 e 95 dias após a semeadura (DAS) e sem aplicação aos 97 dias -testemunha). As variáveis analisadas foram, grau de umidade (%), germinação (%), primeira contagem da germinação (%), índice de velocidade de germinação, emergência de plântulas (%), estande inicial (%), índice de velocidade de emergência, peso de mil sementes (g) e produção (Kg ha -1 ). O grau de umidade das sementes de feijão nas épocas de aplicação do herbicida decresceram, antecipando em ate 14 dias a colheita do feijão. Pela germinação e primeira contagem não foi observado diferença entre os tratamentos. Já para o IVG observou-se resultados superiores aos 83 DAS. Para a porcentagem de emergência e IVE os valores foram inferiores aos 87 e 89 DAS. Em contrapartida, os dados obtidos para o estande inicial não diferiram entre si. Para o peso de mil sementes e produção os resultados foram superiores aos 89 DAS e aos 89 e 95 DAS, respectivamente. A aplicação do dessecante Diquat na cultura do feijoeiro a partir dos 83 dias após a semeadura não afeta a germinação das sementes, porém, reduz de maneira significativa a produção de sementes. Palavra chave: Dessecação, Phaseolus vulgaris, qualidade, vigor, germinação AbstractThe objective of this research was to evaluate the influence of Diquat herbicide application, at different periods, on production and physiological quality of bean seeds, cultivar: Perola. The experimental design used was a randomized block (RBD). The treatments were constituted of application of such herbicide with dosage of 400 g ai / ha in eight stages of application (83, 85, 87, 89, 91, 93 and 95 days after seeding (DAS) and without application with 97 days -witness .) The analyzed variables were moisture content (%), germination (%), first count of germination (%)velocity index of germination, seedling emergence (%), initial stand (%)velocity index of emergency, thousand seed weight (g) and production (kg ha-1). The moisture content of the bean seeds at the times of herbicide application declined, anticipating up

ResumoO teste de tetrazólio é um dos métodos mais promissores para estimar, de forma rápida, a viabilidade e o vigor das sementes. Sua utilização em sementes de melancia requer cuidados na embebição e manuseio pela presença de camada mucilaginosa aderente ao tegumento. O objetivo do trabalho foi definir o tempo de embebição e do método de escarificação para retirada da mucilagem, no pré-condicionamento do teste de tetrazólio, sementes de diferentes cultivares de melancia. As sementes foram imersas em água a 30 o C por 12 e 18 horas, e escarificadas em cal, areia fina e areia grossa. Após corte longitudinal na porção distal ao eixo embrionário, os tegumentos foram retirados e os embriões permaneceram em água por mais 2 horas a 30 o C para remoção manual da membrana remanescente. Após definição do método ideal de pré-condicionamento, os embriões foram imersos em soluções de tetrazólio nas concentrações de 0,075%; 0,5% e 1% por três e quatro horas a 30 o C. A imersão das sementes de melancia em água a 30 o C por 12 horas, retirada da mucilagem com areia fina, corte longitudinal na porção distal ao eixo embrionário e remoção do tegumento, seguido da permanência dos embriões em água por 2 horas a 30 o C para retirada manual da membrana interna e imersão na solução de tetrazólio a 0,075% por 4h a 30 o C são procedimentos adequados para avaliação da qualidade de sementes de melancia. Palavras-chave: Citrullus lanatus, cucurbitáceas, viabilidade, vigor, pré-condicionamento AbstractThe tetrazolium test is one of the most promising methods to estimate in a fast way viability and vigor of seeds. Its usage in watermelon seeds requires some care with the imbibition and handling due to presence of mucilaginous layer adherent to the tegument. The objective of this research work was to define the imbibition time and the method of scarification for removing the mucilage, during preconditioning of the tetrazolium test in watermelon. Seeds from different watermellon cultivars were immersed in water at 30°C from 12 to 18 hours, and sloughed in cal, fine and thick sand. After longitudinal cut in the distal portion to the embryonic axis, the tegument was removed and embryos were kept in water for additonal 2 hours at 30°C for hand removal of the remaining membrane. After definition of the ideal pre -conditioning method, the embryos were immersed in tetrazolium solution in concentrations of 0,075%; 0, 5% and 1% for 3 and 4 hours at 30°C. The immersion of watermelon seeds in water at 30°C for 12 hours, mucilage removal with fine sand, longitudinal cut in the distal portion to the embryonic axis, and removal of tegument, followed by the permanence of embryos in water for 2 hours at 30°C for the hand removal of the internal membrane and immersion in the tetrazolium solution at 0,075% for 4 hours at 30°C are adequate procedures for the evaluation of watermelon seed quality.