Contribution of soil organic carbon to the ion exchange capacity of tropical soils

Highly weathered soils represent about 3 billion ha of the tropical region. Oxisols represent about 60% of the Brazilian territory (more than 5 million km 2), in areas of great agricultural importance. Soil organic carbon (SOC) can be responsible for more than 80% of the cation exchange capacity (CEC) of highly weathered soils, such as Oxisols and Ultisols. The objective of this study was to estimate the contribution of the SOC to the CEC of Brazilian soils from different orders. Surface samples (0.0 to 0.2 m) of 30 uncultivated soils (13 Oxisols, 6 Ultisols, 5 Alfisols, 3 Entisols, I Histosol, 1 Inceptisol. and I Molisol), under native forests and from reforestation sites from Sao Paulo State, Brazil, were collected in order to obtain a large variation of (electro)chemical, physical, and mineralogical soil attributes. Total content of SOC was quantified by titulometric and colorimetric methods. Effective cation exchange capacity (ECEC) was obtained by two methods: the indirect method-summation-estimated the ECECi from the sum of basic cations (Ca+ Mg+ K+ Na) and exchangeable Al; and the direct ECECd obtained by the compulsive exchange method, using unbuffered BaCl2 solution. The contribution of SOC to the soil CEC was estimated by the Bennema statistical method. The amount of SOC var ied from 6.6 g kg(-1) to 213.4 g kg(-1). while clay contents varied from 40 g kg(-1) to 716 g kg(-1). Soil organic carbon contents were strongly associated to the clay contents, suggesting that clay content was the primary variable in controling the variability of SOC contents in the samples. Cation exchange capacity varied from 7.0 mmol(c) kg(-1) to 137.8 mmol(c) kg(-1) and had a positive Correlation with SOC. The mean contribution (per grain) of the SOC (1.64 mmol(c)) for the soil CEC was more than 44 times higher than the contribution of the clay fraction (0.04 mmol(c),). A regression model that considered the SOC content as the only significant variable explained 60% of the variation in the soil total CEC. The importance of SOC was related to soil pedogenetic process, since its contribution to the soil CEC was more evident in Oxisols with predominance of Fe and Al (oxihydr)oxides in the mineral fraction or in Ultisols, that presented illuviated clay. The influence of SOC in the sign and in the magnitude of the net charge of soils reinforce the importance of agricultural management systems that preserve high levels of SOC, in order to improve their sustainability.

Deciphering the weathering processes using environmental mineralogy and geochemistry: Towards an integrated model of laterite and podzol genesis in the Upper Amazon Basin

This article reports major results from collaborative research between France and Brazil on soil and water systems, carried out in the Upper Amazon Basin. It reveals the weathering processes acting in the partly inundated, low elevation plateaus of the Basin, mostly covered by evergreen forest. Our findings are based on geochemical data and mineral spectroscopy that probe the crystal chemistry of Fe and Al in mineral phases (mainly kaolinite, Al- and Fe-(hydr)oxides) of tropical soils (laterites). These techniques reveal crystal alterations in mineral populations of different ages and changes of metal speciation associated with mineral or organic phases. These results provide an integrated model of soil formation and changes (from laterites to podzols) in distinct hydrological compartments of the Amazon landscapes and under altered water regimes. (C) 2010 Academie des sciences. Published by Elsevier Masson SAS. All rights reserved.

SAGE transcript profiling of the juvenile cambial region of Eucalyptus grandis

Despite the importance of Eucalyptus spp. in the pulp and paper industry, functional genomic approaches have only recently been applied to understand wood formation in this genus. We attempted to establish a global view of gene expression in the juvenile cambial region of Eucalyptus grandis Hill ex Maiden. The expression profile was obtained from serial analysis of gene expression (SAGE) library data produced from 3- and 6-year-old trees. Fourteen-base expressed sequence tags (ESTs) were searched against public Eucalyptus ESTs and annotated with GenBank. Altogether 43,304 tags were generated producing 3066 unigenes with three or more copies each, 445 with a putative identity, 215 with unknown function and 2406 without an EST match. The expression profile of the juvenile cambial region revealed the presence of highly frequent transcripts related to general metabolism and energy metabolism, cellular processes, transport, structural components and information pathways. We made a quantitative analysis of a large number of genes involved in the biosynthesis of cellulose, pectin, hemicellulose and lignin. Our findings provide insight into the expression of functionally related genes involved in juvenile wood formation in young fast-growing E. grandis trees.

LEAF AREA REDUCTION IN CORN GROWN IN A TROPICAL REGION OF BRAZIL AND ITS EFFECTS ON AGRONOMIC TRAITS

Global climate change may reduce leaf area in crop plants due to factors such as increasing occurrence of pests and diseases. The aim of this work was to estimate the impact of leaf area reduction on agronomic traits in corn. An experiment simulating leaf area reduction was carried out in a tropical region of Brazil. The agronomic performance of corn plants was evaluated at different percentages of leaf loss. It was observed that leaf area reductions over 41.01% significantly harm yield, mass of 1000 grains, cob density, and stem and root quality Crop improvement programs should take into account the development of genotypes resistant to factors that cause leaf area reduction in tropical crops.

Heteroplasmy in Hair: Study of Mitochondrial DNA Third Hypervariable Region in Hair and Blood Samples

Mitochondrial DNA (mtDNA) analysis has proved useful for forensic identification especially in cases where nuclear DNA is not available, such as with hair evidence. Heteroplasmy, the presence of more than one type of mtDNA in one individual, is a common situation often reported in the first and second mtDNA hypervariable regions (HV1/HV2), particularly in hair samples. However, there is no data about heteroplasmy frequency in the third mtDNA hypervariable region (HV3). To investigate possible heteroplasmy hotspots, HV3 from hair and blood samples of 100 individuals were sequenced and compared. No point heteroplasmy was observed, but length heteroplasmy was, both in C-stretch and CA repeat. To observe which CA ""alleles"" were present in each tissue, PCR products were cloned and re-sequenced. However, no variation among CA alleles was observed. Regarding forensic practice, we conclude that point heteroplasmy in HV3 is not as frequent as in the HV1/HV2.

Myotoxic phospholipases A(2) isolated from Bothrops brazili snake venom and synthetic peptides derived from their C-terminal region: Cytotoxic effect on microorganism and tumor cells

This paper reports the purification and biochemical/pharmacological characterization of two myotoxic phospholipases A(2) (PLA(2)S) from Bothrops brazili venom, a native snake from Brazil. Both myotoxins (MTX-I and II) were purified by a single chromatographic step on a CM-Sepharose ion-exchange column up to a high purity level, showing M-r similar to 14,000 for the monomer and 28,000 Da for the dimer. The N-terminal and internal peptide amino acid sequences showed similarity with other myotoxic PLA2S from snake venoms, MTX-I belonging to Asp49 PLA(2) class, enzymatically active, and MTX-II to Lys49 PLA(2)S, catalytically inactive. Treatment of MTX-I with BPB and EDTA reduced drastically its PLA(2) and anticoagulant activities, corroborating the importance of residue His48 and Ca2+ ions for the enzymatic catalysis. Both PLA(2)S induced myotoxic activity and dose-time dependent edema similar to other isolated snake venom toxins from Bothrops and Crotalus genus. The results also demonstrated that MTXs and cationic synthetic peptides derived from their 115-129 C-terminal region displayed cytotoxic activity on human T-cell leukemia (JURKAT) lines and microbicidal effects against Escherichia coli, Candida albicans and Leishmania sp. Thus, these PLA(2) proteins and C-terminal synthetic peptides present multifunctional properties that might be of interest in the development of therapeutic strategies against parasites, bacteria and cancer. (C) 2008 Elsevier Inc. All rights reserved.

Antitumor effects of snake venom chemically modified Lys49 phospholipase A(2)-like BthTX-I and a synthetic peptide derived from its C-terminal region

The present work evaluates both in vitro and in vivo antitumor activity of BPB-modified BthTX-I and its cationic synthetic peptide derived from the 115-129 C-terminal region. BPB-BthTX-1 presented cytotoxicity of 10-40% on different tumor cell lines, which were also susceptible to the lytic action of the synthetic peptide. Injection of the modified protein or the peptide in mice, 5 days after transplantation of S 180 tumor cells, reduced 30 and 36% of the tumor size on day 14th and 76 and 79% on day 60th, respectively, when compared to the untreated control group. Thus, these antitumor properties might be of interest in the development of therapeutic strategies against cancer. (C) 2009 The International Association for Biologicals. Published by Elsevier Ltd. All rights reserved.

Northern wing, General Purpose North 3, University of Queensland, St Lucia

As seen from Blair Road.

Northern wing, General Purpose North 3, University of Queensland, St Lucia

As seen from Balir Road.

West elevation, General Purpose North 3, University of Queensland, St Lucia

Formal elevation facing University of Queensland entrance roads.

Eastern edge, General Purpose North 3, University of Queensland, St Lucia

As seen from informal courtyard; Duhig Tower beyond.

West elevation, General Purpose North 3, University of Queensland, St Lucia

Formal elevation facing University of Queensland entrance roads.

West elevation, General Purpose North 3, University of Queensland, St Lucia

Formal elevation facing University of Queensland entrance roads.

West elevation, General Purpose North 3, University of Queensland, St Lucia

Formal elevation facing University of Queensland entrance roads.