RESUMO Primavera do Leste é um dos pólos de produção de grãos e fibras do MatoGrosso, com lavouras altamente tecnificadas. Este estudo foi realizado num Latossolo Vermelho-Amarelo da região de Primavera, com objetivo de avaliar a biomassa e a atividade microbiana de solos sob vegetação nativa e sistemas agrícolas anuais e perenes. As amostras de solo foram coletadas em duas profundidades (0-5 e 5-20 cm), no início da estação chuvosa, em áreas sob cultivo de videira (Vitis vinifera), entrelinha e linha, cultivos anuais (soja) e em uma área de vegetação nativa de Cerradão. Foram avaliados o carbono da biomassa microbiana (CBM), carbono prontamente mineralizável e as atividades das enzimas β β β β β-glucosidase, fosfatase ácida e arilsulfatase. Nas duas profundidades avaliadas, os sistemas de uso do solo com culturas perenes e anuais apresentaram reduções médias de 70 % no CBM, em relação à área sob vegetação nativa. O manejo diferenciado na entrelinha do parreiral e a utilização do capim-pé-degalinha (Eleusine indica), como cobertura viva, proporcionaram aumentos no C mineralizável e na atividade das enzimas β β β β β-glucosidase e arilsulfatase nas duas profundidades. Os níveis médios de P no solo sob Cerradão resultaram em valores de atividade da fosfatase ácida inferiores aos dos observados em outros locais do Cerrado. Mesmo assim, na profundidade de 0-5 cm, a atividade da fosfatase ácida no Cerradão foi superior à da entrelinha do parreiral (VE) e à da área com culturas anuais, demonstrando a sua importância na mineralização do fósforo orgânico em áreas sob vegetação nativa. Os resultados obtidos confirmaram a sensibilidade dos parâmetros microbiológicos e bioquímicos para identificar alterações no solo de acordo com os diferentes sistemas de uso da terra.

RESUMO.O presente trabalho tem como objetivo avaliar a influência de diferentes sistemas de manejos, a população microbiana e sua atividade. Para tal, foram coletadas, em outubro de 2006 e março de 2007, amostras de solo na Fazenda Sereno no Município de Jaciara, Estado do Mato Grosso. Retirou-se amostras de solo na profundidade de 0-10 cm, com quatro repetições em cinco áreas com diferentes sistemas de manejos: integração lavoura-pecuária, lavoura de milho/soja, pastagens, vegetação nativa e vegetação nativa em recuperação. Para avaliar o carbono da biomassa microbiana (CBM) e a respiração microbiana (RM) foi utilizado o método do Clorofórmio Fumigação-Incubação (CFI). Já o qCO 2 foi obtido pela relação entre a RM e o CBM. As médias foram comparadas pelo teste de Scott-Knott a 5%. No decorrer das análises, pôde-se observar que as diferentes práticas agrícolas afetam fortemente o solo causando distúrbios na comunidade microbiana que podem, por sua vez, influenciar os processos biogeoquímicos que nele ocorrem. Os dados obtidos permitem, ainda, concluir que: nos sistemas Integração lavoura-pecuária e pecuária a população microbiana é influenciada pelas épocas de coletas. Nesse trabalho, no sistema Integração lavoura-pecuária a atividade microbiana é constante nas diferentes épocas de coleta e os diferentes sistemas de manejos influenciam a atividade metabólica dos microrganismos presentes no solo.Palavras-chave: microrganismos do solo, clorofórmio fumigação-incubação, bioindicadores, quociente metabólico, integração lavoura-pecuária.

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SUMMARYAeschynomene fluminensis Veil., originally obtained from flooded areas of the Pantanal Matogrossense region of Brazil, was grown under stem-flooded or non-flooded conditions for 70 d after inoculation with isolates of photosynthetic stem nodule rhizobia obtained from native A. fluminensis. Stem nodules formed only on submerged stems of flooded plants (mean of 25 per plant), and did not form on aerial parts, although they were capable of growing and fixing N^ after drainage of the stems. Root nodules formed on both non-flooded and flooded plants but were usually decreased in number by flooding (from means of 124 to 51 per plant, respectively). Flooding (and stem-nodulation) resulted in an increase in shoot (and a decrease in root) dry weight, regardless of rhizobial isolate.Stem nodules were attached by a wide collar of aerenchymatous tissue at the base of the nodule. There were large air spaces in the stem where nodules were subtended and these were continuous with nodule aerenchyma/outer corte.x. In addition, aerenchyma and spongy tissue at the base of the nodule connected both flooded and non-flooded root nodules to large intercellular spaces in the root cortex. The stem and root nodules were ovoid in shape, and essentially aeschynomenoid in type, i.e. the central infected tissue was without uninfected, interstitial cells. Root nodules had a similar structure to stem nodules (although stem nodules were generally larger), and flooded root nodules were approximately twice the size of non-flooded nodules. The infected tissue of root and stem nodules consisted of spherical, bacteroid-containing cells containing one or two rod-shaped bacteroids per peribacteroid unit and prominent organelles. Infection threads were observed in root but not in stem nodules.The cortex of stem and root nodules had an apparent oxygen diffusion barrier, consisting of concentric layers of small cells with interlocking cell walls and few intercellular spaces. Cell layers external to these consisted of larger cells and intercellular spaces, with some spaces being occluded with an electron-dense material that contained a glycoprotein recognized by the monoclonal antibodies MAC236 and MAC265. The amount of glycoprotein occlusions did not appear to differ between nodule types or treatments, although stem nodules contained intracellular glycoprotein vesicles adjacent to cell walls. The exterior of the nodules consisted of an epidermis of thin flattened cells with occasional lenticels. Amyloplasts were common in lower stem and hypocotyl nodules, but fewer in flooded or non-flooded root nodules. Upper stem nodules (i.e. those within 6 cm of the water surface) differed from more profoundly submerged stem nodules by having chloroplasts throughout the cortex. Root nodules did not contain chloroplasts, and undifferentiated plastids were found mainly in lower stem nodules.

SUMMARYWe report on the structure of N^-fixing nodules formed on the stem of Discolobium pulchellum Benth., an aquatic legume in the subfamily Papilionoideae, tribe Aeschynomeneae, from the flooded areas in the ' Pantanai Matogrossense' region of Brazil. The stem (and root) nodules were ohligately aquatic, requiring permanent submergence in water or flooded soil, and receive oxygen via profuse aerenchyma covering the lower .stem. Of the 69 isolates of rhizobia isolated from stem and root nodules, 70 % were fast-growing acid producers and 30 "'o were slow growers. The rhizobia were not photosynthetic. Nodules were connected to the stem, and the vascular system from the stem branched throughout the nodule, penetrating the infected tissue within finger-hke ingrowths of cortex. In both stem and root nodule.s, infected tissue was aeschynomenoid or desmodioid, that is, without uninfected (interstitial) cells. The infected cells in stem nodules were vacuolate, with visible infection threads. The inner cortex was rich in amyloplasts and contained the components of an oxygen diffusion barrier (a boundary cell layer without intercellular spaces and glycoprotein occlusions of intercellular spaces in other cell layers). The midcortex, e.\ternaJ to the boundary layer, consisted of loosely-packed cells and these were continuous with stem aerenchyma. The outer part of the nodules was made up of phellogen-derived cells forming a periderm, or 'corky' layer of cells. The periderm formed large lenticels above cortical vascular bundles. These lenticels also connected with the stem aerenchyma. Root nodules differed only in that infected cells were not vacuolate, bacteroids were larger and contained more poK-/y-hydroxybutyrate (PHB) and there was less aerenchyma/ienticellular tissue. Stem and root nodule structure is discussed in terms of adaptations to O^ constraints in an aquatic environment.

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