Conductive Polymer Composites Synthesized from Diacetylene-Functionalized Linseed Oil and MWCNT: Gamma Irradiation and Organic Vapor Sensing

Beca de estancia de Posdoctorado del Dr. Alejandro Ramírez JiménezEpoxidized linseed oil (ELO) was synthesized and functionalized with propargylamine (PA) or 3-ethynylaniline (EA) and the products were crosslinked to obtain the diacetylene-functionalized epoxidized linseed oil polymers which were used as matrices in the preparation of the composites with multiwalled carbon nanotubes (MWCNTs). Electrical resistance at percentages between 4 and 20 wt/wt% of filler was measured and the percolation threshold was calculated, obtaining 1.2 and 1.7% for the composites with EA and PA respectively. Low critical concentration evidenced a good dispersion of the MWCNTs without necessity of any modification. The final products were used in the sensing of acetone, chloroform and ethanol. The electrical resistance changes were measured at different concentrations and the sensibility was calculated. In order to improve stability toward the vapors, composites were irradiated with gamma rays and new sensing was done and compared. The results showed differences in sensibility, selectivity and reproducibility.CONACy

Metales Pesados en Sedimientos de la Zona Costera de la Bahfa de Chetumal, Quintana Roo, Mexico

La contamination de la zona costera de la bahfa de Chetumal fue caracterizadamediante el analisis de metales en sedimentos superficiales (2 a 5 cm) en 27 puntosde muestreo a lo largo de la lfnea de costa de la bahfa de Chetumal, QuintanaRoo, realizando 2 muestreos, uno en temporada de secas en primavera y el otroen temporada de lluvias en el otoiio durante 2001. Se determino la concentracidnde 4 metales (Zn, Pb, Cd y Hg) en los sedimentos de la isobata de 500 m. Losmetales en la temporada de secas presentan una ligera disminucion en los puntos13 al 16 comparados con los de temporada de lluvias, los niveles de Pb y Hg semantienen altos y rebasan los valores normales de las normas oficiales Nacionalese Internationales

Biochemical and functional properties of indigenous Australian herbal infusions

The phytochemical profile, organic acid content, minerals, various antioxidant assays and consumers acceptability of indigenous Australian herbal infusions namely gulban (Melaleuca citrolens), anise myrtle (Syzygium anisatum), and lemon myrtle (Backhousia citriodora) were compared with a commercial green tea (Camellia sinensis). Total phenolic content and catechin derivatives were higher in green tea as compared to indigenous herbal infusions (P < 0.05). Phytochemical profiles showed high levels of caffeine in green tea, but, it was not found in herbal infusions (P < 0.05). Australian indigenous herbal infusions were a good source of calcium and magnesium compared to green tea (P < 0.05). Oxalic acid was higher in green tea, whereas gulban and anise myrtle infusions were rich in citric acid (P < 0.05). Antioxidant activities of green tea and gulban herbal infusions were comparable (P ≥ 0.05). Overall liking scores were higher for herbal infusions compared to green tea (P < 0.05). Indigenous Australian herbal infusions particularly gulban has a potential to become a successful commercial herbal beverage

Effect of Co-Inoculation with Mycorrhiza and Rhizobia on the Nodule Trehalose Content of Different Bean Genotypes

Studies on Rhizobium-legume symbiosis show that trehalose content in nodules under drought stress correlates positively with an increase in plant tolerance to this stress. Fewer reports describe trehalose accumulation in mycorrhiza where, in contrast with rhizobia, there is no flux of carbohydrates from the microsymbiont to the plant. However, the trehalose dynamics in the Mycorrhiza-Rhizobium-Legume tripartite symbiosis is unknown. The present study explores the role of this tripartite symbiosis in the trehalose content of nodules grown under contrasting moisture conditions. Three wild genotypes (P. filiformis, P. acutifolis and P. vulgaris) and two commercial genotypes of Phaseolus vulgaris (Pinto villa and Flor de Mayo) were used. Co-inoculation treatments were conducted with Glomus intraradices and a mixture of seven native rhizobial strains, and trehalose content was determined by GC/MS. The results showed a negative effect of mycorrhizal inoculation on nodule development, as mycorrhized plants showed fewer nodules and lower nodule dry weight compared to plants inoculated only with Rhizobium. Mycorrhizal colonization was also higher in plants inoculated only with Glomus as compared to plants co-inoculated with both microsymbionts. In regard to trehalose, co-inoculation negatively affects its accumulation in the nodules of each genotype tested. However, the correlation analysis showed a significantly positive correlation between mycorrhizal colonization and nodule trehalose content

Optimization of the composting process of sugarcane filter-pressed mud in the Santa Rosalia sugar mill, Tabasco, Mexico

Objective: To optimize the composting process of sugarcane filter-pressed mud, straw, and ash as an alternative to reduce the environmental contamination of sugarcane cultivation in the Santa Rosalía sugar mill (Ingenio Santa Rosalía) of Chontalpa, Tabasco, Mexico.Design/Methodology/Approach: A completely randomized experimental design in a factorial arrangement was used, with compost mixtures and the aeration times as study factors. Ten treatments were generated with six repetitions each. The study variables were pH, organic matter (%), and nitrate (NO 3 - ) and ammonium (NH 4 + ) content.Results: The compost mixture factor had significant effects on compost quality parameters. Aeration times did not affect the quality of the different compost mixtures. Chemical characteristics of pH and organic matter did not present differences between the treatments. Study Limitations/Implications: The use of industrial sugarcane residues generates quality organic fertilizers through the composting process; therefore, it is necessary to test more residues, such as molasses and vinasses.Findings/Conclusions: The 100% sugarcane filter-pressed mud and the 100% sugarcane filter-pressed mud + 0.5% N treatments presented the highest amount of NO 3 - and NH 4 + and were therefore considered the best treatments. All treatments were classified as mature composts, rich in organic matter, with alkaline pH, and made ofsteady materials

Nitrogen forms affect root structure and water uptake in the hybrid poplar

The study analyses the effects of two different forms of nitrogen fertilisation (nitrate and ammonium) on root structure and water uptake of two hybrid poplar (Populus maximowiczii x P. balsamifera) clones in a field experiment. Water uptake was studied using sap flow gauges on individual proximal roots and coarse root structure was examined by excavating 18 whole-root systems. Finer roots were scanned and analyzed for architecture. Nitrogen forms did not affect coarse-root system development, but had a significant effect on fine-root development. Nitrate-treated trees presented higher fine:coarse root ratios and higher specific root lengths than control or ammonium treated trees. These allocation differences affected the water uptake capacity of the plants as reflected by the higher sapflow rate in the nitrate treatment. The diameter of proximal roots at the tree base predicted well the total root biomass and length. The diameter of smaller lateral roots also predicted the lateral root mass, length, surface area and the number of tips. The effect of nitrogen fertilisation on the fine root structure translated into an effect on the functioning of the fine roots forming a link between form (architecture) and function (water uptake)

Changes in the allocation of endogenous strigolactone improve plant biomass production on phosphate-poor soils.

Strigolactones (SLs) are carotenoid-derived phytohormones shaping plant architecture and inducing the symbiosis with endomycorrhizal fungi. In Petunia hybrida, SL transport within the plant and towards the rhizosphere is driven by the ABCG-class protein PDR1. PDR1 expression is regulated by phytohormones and by the soil phosphate abundance, and thus SL transport integrates plant development with nutrient conditions. We overexpressed PDR1 (PDR1 OE) to investigate whether increased endogenous SL transport is sufficient to improve plant nutrition and productivity. Phosphorus quantification and nondestructive X-ray computed tomography were applied. Morphological and gene expression changes were quantified at cellular and whole tissue levels via time-lapse microscopy and quantitative PCR. PDR1 OE significantly enhanced phosphate uptake and plant biomass production on phosphate-poor soils. PDR1 OE plants showed increased lateral root formation, extended root hair elongation, faster mycorrhization and reduced leaf senescence. PDR1 overexpression allowed considerable SL biosynthesis by releasing SL biosynthetic genes from an SL-dependent negative feedback. The increased endogenous SL transport/biosynthesis in PDR1 OE plants is a powerful tool to improve plant growth on phosphate-poor soils. We propose PDR1 as an as yet unexplored trait to be investigated for crop production. The overexpression of PDR1 is a valuable strategy to investigate SL functions and transport routes

A Focus on Natural Variation for Abiotic Constraints Response in the Model Species Arabidopsis thaliana

Plants are particularly subject to environmental stress, as they cannot move from unfavourable surroundings. As a consequence they have to react in situ. In any case, plants have to sense the stress, then the signal has to be transduced to engage the appropriate response. Stress response is effected by regulating genes, by turning on molecular mechanisms to protect the whole organism and its components and/or to repair damage. Reactions vary depending on the type of stress and its intensity, but some are commonly turned on because some responses to different abiotic stresses are shared. In addition, there are multiple ways for plants to respond to environmental stress, depending on the species and life strategy, but also multiple ways within a species depending on plant variety or ecotype. It is regularly accepted that populations of a single species originating from diverse geographic origins and/or that have been subjected to different selective pressure, have evolved retaining the best alleles for completing their life cycle. Therefore, the study of natural variation in response to abiotic stress, can help unravel key genes and alleles for plants to cope with their unfavourable physical and chemical surroundings. This review is focusing on Arabidopsis thaliana which has been largely adopted by the global scientific community as a model organism. Also, tools and data that facilitate investigation of natural variation and abiotic stress encountered in the wild are set out. Characterization of accessions, QTLs detection and cloning of alleles responsible for variation are presented

A Contribution to Identification of Novel Regulators of Plant Response to Sulfur Deficiency: Characteristics of a Tobacco Gene UP9C, Its Protein Product and the Effects of UP9C Silencing

Extensive changes in plant transcriptome and metabolome have been observed by numerous research groups after transferring plants from optimal conditions to sulfur (S) deficiency. Despite intensive studies and recent important achievements, like identification of SLIM1/EIL3 as a major transcriptional regulator of the response to S-deficiency, many questions concerning other elements of the regulatory network remain unanswered. Investigations of genes with expression regulated by S-deficiency stress encoding proteins of unknown function might help to clarify these problems. This study is focused on the UP9C gene and the UP9-like family in tobacco. Homologs of these genes exist in other plant species, including a family of four genes of unknown function in Arabidopsis thaliana (LSU1-4), of which two were reported as strongly induced by S-deficit and to a lesser extent by salt stress and nitrate limitation. Conservation of the predicted structural features, such as coiled coil region or nuclear localization signal, suggests that these proteins might have important functions possibly mediated by interactions with other proteins. Analysis of transgenic tobacco plants with silenced expression of UP9-like genes strongly argues for their significant role in regulation of plant response to S-deficit. Although our study shows that the UP9-like proteins are important components of such response and they might be also required during other stresses, their molecular functions remain a mystery