Flooding tolerance and cell wall alterations in maize mesocotyl during hypoxia.

ABSTRACT - This research aimed to characterize the tolerance to flooding and alterations in pectic and hemicellulose fractions from mesocotyl of maize tolerant to flooding when submitted to hypoxia. In order to characterize tolerance seeds from maize cultivars Saracura BRS-4154 and BR 107 tolerant and sensitive to low oxygen levels, respectively, were set to germinate. Plantlet survival was evaluated during five days after having been submitted to hypoxia. After fractionation with ammonium oxalate 0.5% (w/v) and KOH 2M and 4M, Saracura BRS-4154 cell wall was obtained from mesocotyl segments with different damage intensities caused by oxygen deficiency exposure. The cell wall fractions were analyzed by gel filtration and gas chromatography, and also by Infrared Spectrum with Fourrier Transformation (FTIR). The hypoxia period lasting three days or longer caused cell lysis and in advanced stages plant death. The gelic profile from pectic, hemicellulose 2M and 4M fractions from samples with translucid and constriction zone showed the appearance of low molecular weight compounds, similar to glucose. The main neutral sugars in pectic and hemicellulose fractions were arabinose, xilose and mannose. The FTIR spectrum showed a gradual decrease in pectic substances from mesocotyl with normal to translucid and constriction appearance respectively RESUMO - Objetivou-se caracterizar a tolerancia ao alagamento e alteracoes nas fracoes pecticas e hemicelulosicas de mesocotilos de milho submetidos a hipoxia. Sementes de milho cultivar Saracura BRS-4154 e BR 107, tolerante e sensivel a hipoxia, respectivamente, foram submetidas a germinacao e a sobrevivencia das plantulas em condicoes de hipoxia, foi avaliada durante cinco dias. O material de parede celular, obtido de segmentos de mesocotilos da cultivar Saracura BRS-4154 com diferentes intensidades de danos causados por hipoxia, foi submetido a fracionamento com oxalato de amonio 0,5% e KOH 2M e 4M. As fracoes de parede celular obtidas foram analisadas por cromatografia em gel, cromatografia gasosa e espectro de infravermelho com transformacao dos dados pela serie de Fourrier (FTIR). Periodos de hipoxia superiores a tres dias causaram a lise celular (aparencia translucida),e, em estadios mais avancados, a morte das plantas. O perfil gelico das fracoes pecticas, hemicelulose 2M e 4M das amostras de mesocotilos translucidos e com constricao apresentaram compostos de baixos pesos moleculares semelhantes a glicose. Os principais acucares neutros nas fracoes pecticas e hemicelulosicas foram arabinose, xilose e manose. O espectro de FTIR mostrou um decrescimo gradual nas substancias pecticas do mesocotilo com aparencia normal, para translucido e constricao respectivamente

Manejo das forrageiras dos gêneros Brachiaria e Panicum consorciadas com o milho em sistemas de Integração Lavoura-Pecuária.

bitstream/CNPMS-2010/22387/1/Circ-130.pd

Characterization of maize physiological responses to nitrogen stress by using chlorophyll fluorescence and gas exchange measurements.

Suplemento. Edição dos resumos do IX Congresso Brasileiro de Fisiologia Vegetal, 2003, Atibaia, SP

Co4N/nitrogen-doped graphene: a non-noble metal oxygen reduction electrocatalyst for alkaline fuel cells

Abstract Cobalt-nitride (Co4N) nanoparticle-decorated nitrogen-doped graphene sheets were obtained via the nitrogen doping of a graphene-oxide precursor and simultaneous nitride formation. The non-precious metal catalyst formed in this one-step synthesis exhibits high electrocatalytic oxygen reduction activity and hence provides a promising alternative to conventional Pt/C alkaline fuel cell cathode catalysts. The reported composites were formed from the mixture of lyophilized graphene-oxide nanosheets and cobalt(II) acetate in ammonia atmosphere at 600 °C. The average Co4N particle size increased from 14 to 201 nm with the increase in cobalt content. The oxygen reduction activity of the new catalysts was comparable to that of non-noble metal systems described in the literature, and also to the widely-used carbon black supported platinum catalysts. The highest reduction current density under alkaline conditions was found to be as high as 4.1 mA cm−2 with the corresponding electron transfer number of 3.6. Moreover, the new system outperformed platinum-based composites in terms of methanol tolerance, thus eliminating one of the major drawbacks (besides high price and limited availability), of noble metal catalysts

Combining x-ray real and reciprocal space mapping techniques to explore the epitaxial growth of semiconductors

In the present work, the importance of determining the strain states of semiconductor compounds with high accuracy is demonstrated. For the matter in question, new software titled LAPAs, the acronym for LAttice PArameters is presented. The lattice parameters as well as the chemical composition of Al1-xInxN and Ge1-xSnx compounds grown on top of GaN- and Ge-buffered c-Al2O3 and (001) oriented Si substrates, respectively, are calculated via the real space Bond's method. The uncertainties in the lattice parameters and composition are derived, compared and discussed with the ones found via x-ray diffraction reciprocal space mapping. Broad peaks lead to increased centroid uncertainty and are found to constitute up to 99% of the total uncertainty in the lattice parameters. Refraction correction is included in the calculations and found to have an impact of 0.001 angstrom in the lattice parameters of both hexagonal and cubic crystallographic systems and below 0.01% in the quantification of the InN and Sn contents. Although the relaxation degrees of the nitride and tin compounds agree perfectly between the real and reciprocal-spaces methods, the uncertainty in the latter is found to be ten times higher. The impact of the findings may be substantial for the development of applications and devices as the intervals found for the lattice match the condition of Al1-xInxN grown on GaN templates vary between similar to 1.8% (0.1675-0.1859) and 0.04% (0.1708-0.1712) if derived via the real- and reciprocal spaces methods.This work was supported by the Portuguese Foundation for Science and Technology (FCT) in the framework of the Plurianual Strategic Funding UID/FIS/50010/2019. FO acknowledges the FCT PhD Grant and thanks the Institut fuer Halbleitertechnik, Universitaet Stuttgart for hospitality. The authors acknowledge Professor I Watson and Professor F Schulze from the Universities of Strathclyde, Scotland, United Kingdom, and Stuttgart, Germany for the growth of the nitrides and tin compounds, respectively

The forage yield of Gliricidia sepium during the rainy and dry seasons following pruning management in Brazil.

Gliricidia sepium (Jacq.) Steud. shows relatively little growth variation due to climatic differences throughout the year and between years. The purpose of this study was to evaluate various cutting strategies for the management of Gliricidia for forage production in dry and rainy periods of the year. A randomized-block factorial experimental design (12 × 2) was used for the study. The factorial setup consisted of 12 pruning management treatments (cuttings at 45, 60, 75 and 90 days with 30, 60 and 90 cm residual heights) and two periods (dry and rainy season) with four replicates. There were significant interactions between the management regime and the season for plant height, stem diameter, stem diameter and the weight of both fresh and dry forage. The treatment with a cutting frequency of 90 days and a residual height of 90 cm resulted in the highest final average height and the largest stem diameter in the dry period, with reductions of 7.65 and 1.5%, respectively, during the period of water scarcity. The 90 days × 90 cm treatment resulted in the highest production of fresh and dry forage biomass. Application of different cutting strategies to the Gliricidia plants influenced the diameters of the stems and buds, plant height and accumulation of forage biomass during the rainy and dry seasons. The highest cutting frequency (90 days) and lower intensity cutting (90 cm) provided greater stem diameter, number of shoots and plant height, and the higher forage yield of Gliricidia.Autoria: JOAO AVELAR MAGALHAES. Filiação: UFC [i.e. CPAMN]