Leônidas Paixão Passos

Optimisation of a Capillary Zone Electrophoresis Methodology for Simultaneous Analysis of Organic Aliphatic Acids in Extracts of Brachiaria brizantha

INTRODUCTION Aluminum toxicity is commonly verified in acidic soils, and poses a severe limitation to plant growth and development. Therefore, Al complexation by the root system mucilage, Al complexation by organic compounds that are exuded by the roots and internal metabolic processes must be monitored by organic acids (OA), since they play a central role in these aluminum tolerance mechanisms. OBJECTIVE To optimise a capillary zone electrophoresis method able to perform simultaneous separation of acetic, citric, formic, lactic, malic, oxalic, pyruvic, succinic, tartaric and aspartic acid in plant extract solutions. METHODOLOGY Method optimisation was achieved by a chemometric approach through experimental designs. The optimal condition found was: 20 mmol/L phthalic acid buffer; 0.8 mmol/L cetyltrimethyl-ammonium bromide; pH 3.4 adjusted with tris(hydroxymethyl)aminomethane (around 16 mmol/L); -15 kV of voltage; 25 °C of cartridge temperature; indirect ultraviolet detection at 240 nm; and 25 mbar injection for 2 s, within an analysis time of 4 min. RESULTS As a repeatability test of the optimal condition, 30 replicates were carried out with the same working electrolyte, where the relative standard deviation of each peak ranged from 0.081 to 0.36% (for migration time) and from 2.4 to 4.6% (for peak area). CONCLUSION The methodology was successfully applied to simultaneously determine citric, malic and aspartic acid in roots and leaves extract solutions of Brachiaria brizantha, demonstrating its usefulness to study aluminum tolerance.

Molecular characterization of elephantgrass accessions through RAPD markers

O cultivo do capim-elefante e limitado por variacoes na producao de biomassa e por reducoes na qualidade e disponibilidade de forragem, tornando prioritaria a busca de genotipos com menor sazonalidade de producao. Para verificar a extensao da variabilidade genetica entre cultivares contrastantes, 10 acessos foram analisados via amplificacao do DNA pela tecnica RAPD. Foram utilizados 44 primers aleatorios, que produziram um total de 160 bandas de DNA, sendo que 23% das bandas analisadas foram monomorficas para todos os acessos. Os dados binarios, originados dos geis (1-presenca, 0-ausencia), foram utilizados para gerar uma matriz de distâncias geneticas, que foi utilizada para uma analise de agrupamento segundo o metodo da media das distâncias (UPGMA). Os acessos mais divergentes dos demais foram Cameroon e Vruckwona, com distâncias geneticas medias de 0,34. Os acessos com menores distâncias geneticas medias dos demais foram Pioneiro e CNPGL 27-5, ambos com uma distância genetica media de 0,25. As distâncias geneticas, considerando todas as analises, variaram de 0,06 a 0,43, indicando uma variabilidade genetica pouco acentuada, embora os acessos estudados sejam bastante contrastantes em relacao a morfologia e fisiologia.

Autoclave-assisted acidic extraction of water-soluble carbohydrates in forage grasses

Abstract Methods for extracting water‐soluble carbohydrates (WSC) in plants are often time‐consuming and limited to few samples per run. Aiming at resolving such restraints, the utilization of an autoclave in replacement of the traditional reflux‐based protocol was studied in completely randomized design experiments with five replicates. WSC contents were determined in stocks of 11 standards and samples of 14 grass species, following autoclave‐ or reflux‐assisted hydrolyzation. Results revealed that both methods were equally effective in recovering most standards, and plant WSC levels were similar or only narrowly lower with autoclave. Autoclave was operationally advantageous, allowing for 15‐min concurrent processing of 90 samples against a 150‐min extraction of 4 samples with reflux, and energy savings of more than 87% on a per sample basis. It is concluded that the utilization of autoclave for acidic WSC extraction is feasible and even preferable compared with reflux for the studied standards and grasses.

RESPONSES OF ELEPHANTGRASS TO NUTRIENT SOLUTION PH LEVELS

Abstract Seedlings of elephantgrass (Pennisetumpurpureum, Schum.), cvs. Vruckwona and Napier, were grown in aerated nutrient solution and exposed to pH levels of 4.0, 5.0, 6.0, or 7.0. After 30 days under controlled conditions, the effects on growth were evaluated. Plants exposed to pH 5.0, as compared to those under pH 4.0, showed increases in total leaf area, plant height, number of leaves (NL), and leaf, root, and stem fresh weight. No significant differences were found in stubble fresh weight, maximum individual leaf area, leaf area ratio (LAR), leaf area:plant height ratio, and leaf, root, stem, and stubble dry weight and dry matter percentage. Seedlings exposed to pH 4.0, as compared to those under pH 5.0, exhibited higher leaf:stem ratio on a fresh weight basis (FWR) and a tendency for higher leaf :stem ratio on a dry matter basis (DWR). Cultivar Vruckwona yielded superior results than Napier for most studied parameters, except for NL, LAR, and DWR (in which there were no significant differences) a...

Evaluation of techniques and suitable sample number for soluble carbohydrate extraction in stem bases of elephantgrass

Abstract Methods for extracting soluble carbohydrates were compared, aiming at optimizing sample number and size, for level determination using Teles’ reagent. Oven‐dried ground stem basal segments of elephantgrass (Pennisetum purpureum, Schum.) cv. Napier, carbohydrate standards (glucose, maltose, sucrose, and starch), and sample‐standard combinations (CSs) were extracted through the following procedures: (a) REF: reflux for 180 min (in 0.6N HCl); (b) SHA: orbital shaking for 60 min (in 50% ethanol), followed by an acidic hydrolysis (1.2N HCl) in water bath (90–100°C) for 60 min, and neutralization with 5% NaOH; (c) HET: 80% ethanol overnight and water bath for 180 min; (d) ETH: 0.6N HCl (in 80% ethanol) overnight and water bath for 180 min; and (e) DIG: 80% ethanol overnight, addition of 1.2N HCl, and water bath for 60 min. REF yielded the highest extraction level in the elephantgrass sample, followed by ETH and SHA. Levels with HET and DIG were the lowest. However, REF was excessively time consuming an...