Papers by Ronald Maldonado Rodriguez
In this paper we show that chlorophyll a fluorescence signals analysed with the self-organizing m... more In this paper we show that chlorophyll a fluorescence signals analysed with the self-organizing map (SOM) can be used as a routine tool for the monitoring and classification of pea varieties (Pisum sativum) according to their degree of resistance against drought stress. Fluorescence kinetics measurements were obtained from non-stressed plants. The aim of this study is to evaluate the applicability of artificial intelligence techniques in eco-physiological research. Our goal is to provide a fast tool that will contribute to the knowledge needed to develop strategies that would help to decrease the impact of environmental stress in agriculture and forestry.
In this work it is presented a methodology for the development of a pattern recognition system us... more In this work it is presented a methodology for the development of a pattern recognition system using classification methods as discriminant analysis and artificial neural networks. In this methodology, the statistical analysis is contemplated, with the purpose of retaining the observations and the important characteristics that can
produce an appropriate classification, and allows, as well, to detect outliers’ observations, multicolinearity between variables, among other things.
En este trabajo se presenta una aplicación en reconocimiento de patrones, utilizando redes neuron... more En este trabajo se presenta una aplicación en reconocimiento de patrones, utilizando redes neuronales artificiales para analizar señales de fluorescencia clorofílica (FC), con el fin de identificar y clasificar grupos de plantas de Vigna unguiculata (L.) Walp (fríjol) cultivadas en medios hidropónicos que contenían diferentes cantidades de nitrógeno (N) y las señales de fluorescencia de otro grupo de plantas cuyas semillas fueron inoculadas antes de su germinación con la bacteria Rhizobium variedad NGR232. Previo al entrenamiento neuronal se realizó un exhaustivo análisis estadístico multivariante, con la finalidad de detectar diferencias en los vectores de medias de los medios de cultivo y reducir el número de variables o puntos de las curvas de fluorescencia. El objetivo principal de este trabajo es desarrollar una herramienta para identificar la carencia de N en plantas de fríjol y otras leguminosas de mayor producción en agricultura. (N) and fluorescence signals from another group of plants whose seeds were inoculated prior to germination with the NGR232 variety Rhizobium bacteria. Before the ANN training, it was held an exhaustive multivariate statistical analysis for identifying differences among the means vectors of the growth media and reducing the numbers of variables or fluorescence curve points. The main objective of this work is to develop a tool for identifying N deficiency in pea's plants and other legumes with high production in agriculture.
Intention, Goal, Scope, Background. Cyanobacteria have the natural ability to degrade moderate am... more Intention, Goal, Scope, Background. Cyanobacteria have the natural ability to degrade moderate amounts of organic pollut-ants. However, when pollutant concentration exceeds the level of tolerance, bleaching of the cells and death occur within 24 hours. Under stress conditions, cyanobacterial response includes the short-term adaptation of the photosynthetic apparatus to light quality, named state transitions. Moreover, prolonged stresses produce changes in the functional organization of phycobilisomes and in the core-complexes of both photosystems, which can result in large changes in the PS II fluorescence yield. The localization of ferredoxin-NADP+ reductase (FNR) at the ends of some peripheral rods of the cyanobacterial phyco-bilisomes, makes this protein a useful marker to check phyco-bilisome integrity.
Objective. The goal of this work is to improve the knowledge of the mechanism of action of a very potent pesticide, lindane (γ-hexaclorociclohexane), in the cyanobacterium Anabaena sp., which can be considered a potential candidate for bioremediation of pesticides. We have studied the effect of lindane on the pho-tosynthetic apparatus of Anabaena using fluorescence induc-tion studies. As ferredoxin-NADP+ reductase plays a key role in the response to oxidative stress in several systems, changes in synthesis, degradation and activity of FNR were analyzed. Immunolocalization of this enzyme was used as a marker of phycobilisome integrity. The knowledge of the changes caused by lindane in the photosynthetic apparatus is essential for ra-tional further design of genetically-modified cyanobacteria with improved biorremediation abilities.
Methods. Polyphasic chlorophyll a fluorescence rise measure-ments (OJIP) have been used to evaluate the vitality and stress adaptation of the nitrogen-fixing cyanobacterium Anabaena PCC 7119 in the presence of increasing concentrations of lindane. Effects of the pesticide on the ultrastructure have been investi-gated by electron microscopy, and FNR has been used as a marker of phycobilisome integrity.
Results and Discussion. Cultures of Anabaena sp. treated with moderate amounts of lindane showed a decrease in growth rate followed by a recovery after 72 hours of pesticide treatment. Concentrations of lindane below 5 ppm increased the photo-synthetic performance and activity of the cells. Higher amounts of pesticide caused a decrease in these activities which seems to be due to a non-competitive inhibition of PS II. Active PS II units are converted into non-QA reducing, so called heat sink centers. Specific activity and amount of FNR in lindane-treated cells were similar to the values measured in control cultures. Release of FNR from the thylakoid after 48 hours of exposure to 5 ppm of lindane towards the cytoplasm was detected by immunogold labeling and electron microscopy.
Conclusions. From these results, we conclude that the photo-synthetic performance and activity of the cells are slightly in-creased in the presence of lindane up to 5 ppm. Moreover, in those conditions, lindane did not produce significant changes in the synthesis, degradation or activity of FNR. The high capabil-ity of Anabaena to tolerate lindane makes this cyanobacterium a good candidate for phytoremediation of polluted areas.
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Papers by Ronald Maldonado Rodriguez
produce an appropriate classification, and allows, as well, to detect outliers’ observations, multicolinearity between variables, among other things.
Objective. The goal of this work is to improve the knowledge of the mechanism of action of a very potent pesticide, lindane (γ-hexaclorociclohexane), in the cyanobacterium Anabaena sp., which can be considered a potential candidate for bioremediation of pesticides. We have studied the effect of lindane on the pho-tosynthetic apparatus of Anabaena using fluorescence induc-tion studies. As ferredoxin-NADP+ reductase plays a key role in the response to oxidative stress in several systems, changes in synthesis, degradation and activity of FNR were analyzed. Immunolocalization of this enzyme was used as a marker of phycobilisome integrity. The knowledge of the changes caused by lindane in the photosynthetic apparatus is essential for ra-tional further design of genetically-modified cyanobacteria with improved biorremediation abilities.
Methods. Polyphasic chlorophyll a fluorescence rise measure-ments (OJIP) have been used to evaluate the vitality and stress adaptation of the nitrogen-fixing cyanobacterium Anabaena PCC 7119 in the presence of increasing concentrations of lindane. Effects of the pesticide on the ultrastructure have been investi-gated by electron microscopy, and FNR has been used as a marker of phycobilisome integrity.
Results and Discussion. Cultures of Anabaena sp. treated with moderate amounts of lindane showed a decrease in growth rate followed by a recovery after 72 hours of pesticide treatment. Concentrations of lindane below 5 ppm increased the photo-synthetic performance and activity of the cells. Higher amounts of pesticide caused a decrease in these activities which seems to be due to a non-competitive inhibition of PS II. Active PS II units are converted into non-QA reducing, so called heat sink centers. Specific activity and amount of FNR in lindane-treated cells were similar to the values measured in control cultures. Release of FNR from the thylakoid after 48 hours of exposure to 5 ppm of lindane towards the cytoplasm was detected by immunogold labeling and electron microscopy.
Conclusions. From these results, we conclude that the photo-synthetic performance and activity of the cells are slightly in-creased in the presence of lindane up to 5 ppm. Moreover, in those conditions, lindane did not produce significant changes in the synthesis, degradation or activity of FNR. The high capabil-ity of Anabaena to tolerate lindane makes this cyanobacterium a good candidate for phytoremediation of polluted areas.