Luz Marina Melgarejo

Principal component analysis of changes due to water stress for some osmolytes, pigments and antioxidant enzymes in Gmelina arborea Robx: leaves from trees planted in northern Colombia

Gmelina arborea e uma especie de alto impacto economico devido a vantagens como arvore madeireira de rapido crescimento. A G. arborea e plantada na costa norte da Colombia, especialmente nas planicies secas do Caribe. No entanto, condicoes de deficit hidrico a que estao periodicamente submetidos, gera perdas nas plantacoes. Neste estudo mediram se a atividade da catalase, peroxidase e ascorbato peroxidase, assim como o conteudo de acucares totais, acucares redutores, proline, carotenoides, clorofila A, B em folhas coletadas em tres estacoes climaticas diferentes. Um estudo de analises de componentes principais mostrou que o comportamento das variaveis medidas depende tanto da idade quanto do tempo de amostragem, alem de uma correlacao inversa entre as variaveis de clorofila A, B e total e as outras variaveis medidas. Gmelina arborea is a tree having great economic impact due to its advantages as a fast-growing timber tree. G. arborea is currently being planted on the North Coast of Colombia, especially on the dry plains near the Caribbean. However, the stress conditions produced by drought to which they are periodically subjected lead to plantation loss. This study was thus aimed at measuring catalase, peroxidase and ascorbate peroxidase activities as well as total sugar, reducing sugar, proline, carotenoids, chlorophyll A, B and total chlorophyll content in G. arborea leaves sampled during three seasons of the year. Principal component analysis showed that the measured variables had patterns depending on age and season, in addition to an inverse correlation between chlorophyll A, B and total chlorophyll and the other measured variables.

Supramolecular Characterization of Humic Acids Obtained through the Bacterial Transformation of a Low Rank Coal

The humic acid (HA) obtained with the activity of three bacterial strains that transformed a lignite-type low rank coal (LRC) and released humified organic matter (HOM) was characterized. The HA obtained with the activity of Bacillus mycoides, Microbacterium sp. and Acinetobacter baumannii were compared with HA obtained with the traditional alkaline extraction method using NaOH 0.5 M (HA-NaOH). These characterizations included the elemental composition (C, H, N, O), Fourier transform infrared (FTIR) analysis, cross polarization-magic angle spinning-nuclear magnetic resonance (C-CPMAS-NMR), tetramethylammonium hydroxide (TMAH)-thermochemolysis followed by gas chromatography-mass spectrometry (GC-MS) and size exclusion chromatography. The two evaluated HA types showed differences in the elemental composition, aromaticity degree, content of aliphatic groups, molecular weight, polydispersity, profile of the spectra C-CPMAS-NMR and products of TMAH-thermochemolysis. The results indicate that the process of biotransformation of LRC with bacterial activity results in the structural transformations of HA, which leads to the formation of HA with a lower degree of aromaticity, more of a hydrophilic tendency, lower oxygen content, enriched with nitrogenated functional groups and polar aliphatic chains, as compared with HA-NaOH. The HA generated with the three bacterial strains exhibited a high structural similarity to each other; however, some differences were evident in the type of metabolites generated by the TMAH-thermochemolysis of the HA obtained with B. mycoides, as well as a higher polydispersity for the HA generated with A. baumannii.