Produção de resíduos vegetais em áreas de cerrados do Brasil

Litter production was measured in Brazilian Cerrado and Cerradão during three successive years. The average yearly production of total litter is 7,800 kg/ha-1 and 2,100 kg/ha-1 in Cerradão and Cerrado, respectively. The leaf-litter (including grasses) represents 76.7% of the total litter in Cerradão and 84% in Cerrado. The rates of litter decomposition determined by direct litter-bag technique are very slow on surface in both ecosystems. The litters from Cerrado and Cerradão have almost the same nutrient storage ability. Samples of litter composed of the parts of predominant plants contain 0.82%-0.85% of N, 0.06% P, 0.16% K, 0.32%-0,34% Ca and 0.12%-0.14%Mg.Foram efetuadas avaliações de produção de resíduos vegetais de Cerrado e Cerradão, durante três anos consecutivos. A produção média anual de resíduos vegetais foi de 7.800 e 2.100 kg/ha no Cerradão e Cerrado, respectivamente. As folhas senescentes (incluindo gramíneas) representam 76,7% da produção total de resíduos de biomassa no Cerradão, e 84% no Cerrado. A taxa de decomposição deste material foi determinada diretamente em sacos de tela de nylon, sendo considerada muito baixa em ambos os ecosistemas. Os resíduos vegetais coletados no Cerrado e no Cerradão apresentaram semelhante composições de nutrientes: 0,82-0.85% de N; 0,06% de P; 0,16% de K; 0,32%-0,34% de Ca e 0,12-0,14% de Mg

Sobrevivência de estirpes de Rhizobium japonicum na superfície de sementes de soja inoculadas

The objective of this work was to study the possibility of recommending inoculation of soybean seeds before the planting time. For this purpose, the effect of inoculum formulation (water, sucrose solution (25%) and diesel oil as binders) and storage time (0, 1, 2, 4, 6 and 8 days) on the survival of Rhizobium on the surface of inoculated soybean seed was evaluated. Four experiments were carried out: two in the glasshouse and two in the field in Dark-Red and Yellow-Red Latossols at the Centro de Pesquisa Agropecuária dos Cerrados (CPAC) of EMBRAPA. In general, storage time did not affect Rhizobium survival. However, in the glasshouse experiments, nodulation in treatments with sucrose and water even with no storage period, were significantly greater than treatments with diesel oil. Although good nodulation was obtained with water alone, it was poorer than with sucrose. Results obtained under field conditions confirmed those from the glasshouse, indicating that if kept at an ambient temperature, inoculated soybean seeds can be stored for up to four days without affecting nodulation or grain production.Objetivou-se neste trabalho estudar a possibilidade de recomendar a inoculação da soja com Rhizobium antes do plantio. Para isto, avaliou-se o efeito de formas de inoculação (água, solução de sacarose 25% e óleo diesel como adesivos) e do período de armazenamento (0, 1, 2, 4, 6 e 8 dias) na sobrevivência do rizóbio na superfície da semente inoculada. Foram conduzidos 4 experimentos: dois em casa de vegetação e dois no campo, em Latossolos Vermelho-Escuro e Vermelho-Amarelo, no Centro de Pesquisa Agropecuária dos Cerrados, da EMBRAPA. De modo geral, não houve efeito do período de armazenagem na sobrevivência do rizóbio. Nos experimentos de casa de vegetação, a nodulação nos tratamentos com sacarose e água, mesmo no tempo zero de armazenamento, foi significativamente superior ao tratamento com óleo diesel. No tratamento com água, apesar de ter sido obtida uma boa nodulação, esta foi inferior à dos tratamentos com sacarose. Em condições de campo, foram confirmados os resultados de casa de vegetação, evidenciando a possibilidade de se estocar, à temperatura ambiente, sementes de soja inoculadas, isto é, revestidas com inoculante, por um período de até quatro dias, sem prejuízo para nodulação e produção de grãos

Efeitos da inundação na nodulação e desenvolvimento de leguminosas forrageiras tropicais

Three greenhouse experiments were carried out to study the effects of: a) flooding for 20 day periods on plants of different ages; b) increasing periods of flooding; c) increasing moisture levels during the experimental period. The first experiment was carried out in two hydromorphic soils with the soybean cultivar Santa Maria (Glycine max). Assimilation of mineral N as well as symbiotic N stopped after flooding at any age. While nodules on younger plants were maintained, but did not grow, those on 45 day old plants disappeared almost entirely. The second experiment was carried out in one hydromorphic soil with Stylosanthes guyanensis, Phaselous atropurpureus and Centrosema pubescens. S. guyanensis appeared to be the most tolerant species to longer flooding periods up to 45 days while C. pubescens was the most affected. Rotting of roots and nodules was more pronounced on C. pubescens, and new roots and nodules were regenerated in the water above the soil. None of the plants died during the 45 day flooding period. The third experiment was carried out in vermiculite with the forage soybean Santa Maria (Glycine max). Nodule weight and plant growth increased up to 100% of the water holding capacity of the vermiculite, but decreased at 135%. C. pubescens was less affected by water stress than was soybean but was more affected by excess water. While nodule numbers of soybeans, increased up to 135% water holding capacity, those of C. pubescens decreased above 65%.Foram feitos três experimentos em casa de vegetação com leguminosas forrageiras tropicais para estudar os efeitos de: a) períodos de 20 dias de inundação em plantas de diferentes idades; b) períodos crescentes de inundação em plantas já estabelecidas, e ainda, c) níveis crescentes de umidade durante todo o ciclo. No primeiro experimento, que foi feito com dois solos de baixada, a soja forrageira (Glycine max) mostrou que tanto a assimilação do N mineral, como a do simbiótico, parou com a inundação de 4 cm acima do nível do solo, havendo queda de todos os nódulos quando a inundação foi iniciada 50 dias após o plantio, enquanto em plantas mais novas os nódulos se mantiveram. A fixação de N2 possibilitou maior desenvolvimento das plantas do que a adubação com N mineral na base de 180 kg/ha. No segundo experimento, que foi feito com as três leguminosas forrageiras Stylosanthes guyanensis, Phaseolus atropurpureus e Centrosema pubescens num solo de baixada, verificou-se que a primeira foi a espécie mais tolerante à inundação durante períodos mais prolongados, de até 45 dias, enquanto a C. pubescens pareceu ser a espécie mais sensível, notando-se a decomposição completa das raízes e nódulos no solo inundado por mais de 30 dias e o decréscimo progressivo da produção quando comparada com as testemunhas. O P. atropurpureus ocupou posição intermediária. O apodrecimento das raízes no solo inundado foi acompanhado do aparecimento de raízes e nódulos na água acima do solo e nenhuma das três espécies chegou a morrer após 45 dias de inundação. No terceiro experimento, que foi feito com soja forrageira (Glycine max, cultivar Santa Maria) e Centrosema pubescens (Jitirana) em vermiculita, observou-se aumento do peso de nódulos e do desenvolvimento das plantas até 100% da capacidade de retenção de água da vermiculita, mas um decréscimo com 135%. A C. pubescens foi menos afetada pela deficiência da água e mais pelo excesso do que a soja Santa Maria. Enquanto o número de nódulos da soja aumentou até 135% de umidade, o da C. pubescens já diminuiu acima de 65%

Planting date of peas Pisum sativum for seed production in Central Brazil

Foi realizado um ensaio ecológico visando a determinação da época mais propícia à semeadura de ervilha (Pisum sativum L.) no Brasil Central, para a obtenção de sementes, aproveitando-se a adubação residual em um latossolo fase cerrado, anteriormente cultivado com milho doce. Foram utilizadas as cultivares Resistant Early Perfection 326, de origem norte-americana e Roi des Fins Verts, de origem marroquina, em cinco épocas de semeadura. As melhores épocas de semeadura situaram-se no mês de abril até os primeiros dez dias de maio, mas ambas as cultivares apresentaram, em todas as épocas testadas, produtividade elevada (produções de 2.187 a 3.437 kg/ha) se comparada com as produções obtidas no Rio Grande do Sul, onde estas têm ultrapassado 1.800 kg/ha. Os resultados obtidos sugerem a possibilidade da utilização das regiões de cerrado do Brasil Central para a obtenção de sementes de ervilha, abrindo amplas perspectivas para a agricultura nestas áreas e, aparentemente, solucionando o maior problema dessa cultura em nosso País, ou seja, a produção de sementes.A date of planting experiment using peas was conducted in Central Brazil on a Red Dark Latosol Soil. An American variety, Resistant Early Perfection 326, and a variety from Morocco, Roi des Fins Verts, were planted on five different planting dates. The best planting date was between April 1st and May 10th. Both varieties showed high yields at all planting dates. Yields varied from 2,187 to 3,434 kg/ha, as compared with Rio Grande do Sul yields, which did not exceed 1,800 kg/ha. These results indicated great agricultural potential for pea seed production in this area. Seed production is considered one of the most limiting factors for this crop in Brazil

Spontaneous streptomycin resistance and efficiency of Rhizobium strains native in Brazilian cerrados associated with Stylosanthes

Foram efetuados isolamentos de Rhizobium sp nativos nos Cerrados, associados a Stylosanthes spp, com o objetivo de estudar a natureza dos fatores que interferem no estabelecimento das estirpes de Rhizobium inoculadas, e de avaliar o potencial de fixação de N2 das estirpes nativas. Dentre 122 estirpes isoladas em solo sob Cerrado cultivado, 35% foram resistentes a concentrações iguais ou superiores a 40 μg/ml, enquanto que apenas 10% dentre 92 estirpes isoladas em solo sob Cerrado virgem apresentaram esse nível de resistência. Esses dados sugerem que modificações ecológicas promovidas pelo cultivo dos Cerrados podem induzir a vantagens competitivas para estirpes de Rhizobium sp. resistentes à estreptomicina. Experimentos conduzidos em vasos Leonard com areia e solução nutritiva esterilizada indicaram que cerca de 61% das estirpes isoladas em S. guianensis var. Canescens e S. grandifolia eram pouco ou moderadamente efetivas no hospedeiro homólogo, enquanto que apenas 14% das estirpes apresentaram um nível elevado de fixação do N2. Esse baixo índice de estirpes eficientes sugere a necessidade de se iniciar um trabalho de seleção de Rhizobium sp. adaptado às condições dos Cerrados, visando a produção de inoculantes de alta qualidade para a região.Rhizobium strains were isolated from nodules of Stylosanthes spp. in undisturbed or cultivated Cerrado soils that have never been inoculated, in order to study the nature of the factors that affect stablishment of Rhizobium strains introduced in these soils, as well as to evaluate the N2 fixing capacity of the native strains. Streptomycin resistance level of the Rhizobium strains were tested in yeast-mannitol-agar plates. Among 122 strains isolated in cultivated Cerrado, 35%  were resistant to concentrations equal or above 40 μg/ml, while only 10% within 92 strains isolated in undisturbed Cerrados were resistant to that level. These data suggest that the ecological changes caused by cultivation of virgin savanna land result in competitive advantages for Streptomycin resistent Rhizobium strains. Experiments carried out in Leonard jar assemblies with san and sterilized solution indicated that 61% of the strains isolated in S. guianensis var. Canescens and S. grandifolia were low or moderately effective in the homologous host, while only 14% of the strains had a high level of N2 fixation. This low percentage of efficient strains suggests the necessity of a Rhizobium strain selection program adapted to the Cerrado conditions, aiming to obtain high quality inoculant for the Cerrados region

Avaliação de cultivares de soja, sob manejo orgânico, para fins de adubação verde e produção de grãos.

O objetivo deste trabalho foi avaliar o desempenho de seis cultivares de soja, sob manejo orgânico, para fins de adubação verde e produção de grãos. Utilizou-se delineamento experimental de blocos casualizados, com quatro repetições por tratamento (cultivar). Na época da colheita, 81 dias após a emergência das plântulas, todas as cultivares testadas (Celeste, Surubi, Campo Grande, Mandi, Lambari e Taquari) mostraram excelente nodulação, variando de 545 a 760 mg/planta de massa nodular seca. As cultivares Celeste e Taquari, que produziram, respectivamente, 8,33 e 7,12 t ha-1 de biomassa seca da parte aérea, apresentaram outras características agronômicas vantajosas, tais como: ciclo curto, alta acumulação de nutrientes (N, P, K, Ca e Mg) nos tecidos verdes e bom rendimento de sementes. Esses caracteres indicam potencial de 'Celeste' e 'Taquari' para adubação verde de verão em sistemas de agricultura orgânica. Cinco das cultivares avaliadas revelaram tendência ao acamamento, porém dentro de níveis aceitáveis. As cultivares Celeste, Surubi, Campo Grande, Mandi e Taquari suplantaram em 23%, 32%, 33%, 44% e 70%, respectivamente, a média nacional de produtividade de soja, estimada em 2.398 kg ha-1 nas últimas três safras

Signal transduction-related responses to phytohormones and environmental challenges in sugarcane

BACKGROUND: Sugarcane is an increasingly economically and environmentally important C4 grass, used for the production of sugar and bioethanol, a low-carbon emission fuel. Sugarcane originated from crosses of Saccharum species and is noted for its unique capacity to accumulate high amounts of sucrose in its stems. Environmental stresses limit enormously sugarcane productivity worldwide. To investigate transcriptome changes in response to environmental inputs that alter yield we used cDNA microarrays to profile expression of 1,545 genes in plants submitted to drought, phosphate starvation, herbivory and N(2)-fixing endophytic bacteria. We also investigated the response to phytohormones (abscisic acid and methyl jasmonate). The arrayed elements correspond mostly to genes involved in signal transduction, hormone biosynthesis, transcription factors, novel genes and genes corresponding to unknown proteins. RESULTS: Adopting an outliers searching method 179 genes with strikingly different expression levels were identified as differentially expressed in at least one of the treatments analysed. Self Organizing Maps were used to cluster the expression profiles of 695 genes that showed a highly correlated expression pattern among replicates. The expression data for 22 genes was evaluated for 36 experimental data points by quantitative RT-PCR indicating a validation rate of 80.5% using three biological experimental replicates. The SUCAST Database was created that provides public access to the data described in this work, linked to tissue expression profiling and the SUCAST gene category and sequence analysis. The SUCAST database also includes a categorization of the sugarcane kinome based on a phylogenetic grouping that included 182 undefined kinases. CONCLUSION: An extensive study on the sugarcane transcriptome was performed. Sugarcane genes responsive to phytohormones and to challenges sugarcane commonly deals with in the field were identified. Additionally, the protein kinases were annotated based on a phylogenetic approach. The experimental design and statistical analysis applied proved robust to unravel genes associated with a diverse array of conditions attributing novel functions to previously unknown or undefined genes. The data consolidated in the SUCAST database resource can guide further studies and be useful for the development of improved sugarcane varieties

Effects of Immunization With the Soil-Derived Bacterium Mycobacterium vaccae on Stress Coping Behaviors and Cognitive Performance in a "Two Hit" Stressor Model

Previous studies demonstrate that Mycobacterium vaccae NCTC 11659 (M. vaccae), a soil-derived bacterium with anti-inflammatory and immunoregulatory properties, is a potentially useful countermeasure against negative outcomes to stressors. Here we used male C57BL/6NCrl mice to determine if repeated immunization with M. vaccae is an effective countermeasure in a "two hit" stress exposure model of chronic disruption of rhythms (CDR) followed by acute social defeat (SD). On day -28, mice received implants of biotelemetric recording devices to monitor 24-h rhythms of locomotor activity. Mice were subsequently treated with a heat-killed preparation of M. vaccae (0.1 mg, administered subcutaneously on days -21, -14, -7, and 27) or borate-buffered saline vehicle. Mice were then exposed to 8 consecutive weeks of either stable normal 12:12 h light:dark (LD) conditions or CDR, consisting of 12-h reversals of the LD cycle every 7 days (days 0-56). Finally, mice were exposed to either a 10-min SD or a home cage control condition on day 54. All mice were exposed to object location memory testing 24 h following SD. The gut microbiome and metabolome were assessed in fecal samples collected on days -1, 48, and 62 using 16S rRNA gene sequence and LC-MS/MS spectral data, respectively; the plasma metabolome was additionally measured on day 64. Among mice exposed to normal LD conditions, immunization with M. vaccae induced a shift toward a more proactive behavioral coping response to SD as measured by increases in scouting and avoiding an approaching male CD-1 aggressor, and decreases in submissive upright defensive postures. In the object location memory test, exposure to SD increased cognitive function in CDR mice previously immunized with M. vaccae. Immunization with M. vaccae stabilized the gut microbiome, attenuating CDR-induced reductions in alpha diversity and decreasing within-group measures of beta diversity. Immunization with M. vaccae also increased the relative abundance of 1-heptadecanoyl-sn-glycero-3-phosphocholine, a lysophospholipid, in plasma. Together, these data support the hypothesis that immunization with M. vaccae stabilizes the gut microbiome, induces a shift toward a more proactive response to stress exposure, and promotes stress resilience. &nbsp;</p

Neuronal development is promoted by weakened intrinsic antioxidant defences due to epigenetic repression of Nrf2

Forebrain neurons have weak intrinsic antioxidant defences compared with astrocytes, but the molecular basis and purpose of this is poorly understood. We show that early in mouse cortical neuronal development in vitro and in vivo, expression of the master-regulator of antioxidant genes, transcription factor NF-E2-related-factor-2 (Nrf2), is repressed by epigenetic inactivation of its promoter. Consequently, in contrast to astrocytes or young neurons, maturing neurons possess negligible Nrf2-dependent antioxidant defences, and exhibit no transcriptional responses to Nrf2 activators, or to ablation of Nrf2’s inhibitor Keap1. Neuronal Nrf2 inactivation seems to be required for proper development: in maturing neurons, ectopic Nrf2 expression inhibits neurite outgrowth and aborization, and electrophysiological maturation, including synaptogenesis. These defects arise because Nrf2 activity buffers neuronal redox status, inhibiting maturation processes dependent on redox-sensitive JNK and Wnt pathways. Thus, developmental epigenetic Nrf2 repression weakens neuronal antioxidant defences but is necessary to create an environment that supports neuronal development