Remediation effect of compost on soluble mercury transfer in a crop of Phaseolus vulgaris.

We studied the dynamics of mercury (Hg) transfer in Phaseolus vulgaris plants grown in soil with Hg-doped compost at the maximum levels permitted by Colombian law on organic amendments. Quantitative evaluation of transfer was made in different plant organs: roots, stem, leaves, pods and seeds. Matrix effect was determined in doped soil assays, using soil with and without addition of compost. Results showed that the use of organic matter reduced Hg transfer to the plant and the amount transferred was differentially distributed to the organs. We observed an inverse relationship between concentration and distance from the body to the root. It was evident that transfer was mediated by quantitative factors; the greater the presence of mercury in soil, the larger the amount that will be transferred. Results also indicate the remedial effect of compost and the presence of a barrier, at the root level, against mercury translocation to the plant aerial parts.

Actividad insecticida de una emulsión aceite/agua del aceite esencial de Eucalyptus tereticornis / Insecticide activity of oil/water emulsion of Eucalyptus tereticornis essential oil

Introducción: el aceite esencial extraído de especies del género Eucalyptus, entre estas Eucalyptus tereticornis, ofrece un importante potencial para el control de hongos patógenos e insectos plaga y de importancia médica. Objetivo: evaluar la actividad anti-insecto (aguda, crónica y repelente) de una emulsión aceite/agua del aceite esencial de Eucalyptus tereticornis, en función de su composición química y fraccionamiento. Métodos: se prepararon emulsiones aceite/agua con aceite esencial previamente extraído, separado y caracterizado, y 2 de sus fracciones (A y B). Se evaluó su actividad anti-insecto mediante bioensayos con Drosophila melanogaster. Se determinó la fitotoxicidad foliar sobre plántulas de Phaseolus vulgaris. Resultados: el aceite completo mostró considerable actividad repelente e insecticida aguda que guarda relación con su composición química. La actividad insecticida aguda de las fracciones disminuyó de manera notable con respecto a la mostrada por el aceite completo, sin embargo, no se observaron efectos significativos sobre la actividad repelente. En ningún caso se presentó fitotoxicidad foliar sobre frijol. Conclusión: el aceite esencial de esta especie de eucalipto posee actividad anti-insecto considerable y podría formularse directamente como insecticida para el control de insectos de interés agrícola y médico.

Introduction: the essential oil extracted from Eucalyptus species, including Eucalyptus tereticornis, offers significant potential for control of fungal pathogens and insect pests and medical importance. Objectives: to evaluate the anti-insect activity (acute, chronic and repellent) of an oil/water emulsion of Eucalyptus tereticornis essential oil in terms of their chemical composition. Methods: oil/water emulsion was prepared with essential oil previously extracted, separated and characterized, and two of its fractions (A and B). Their anti-insect activity was evaluated through bioassays on Drosophila melanogaster. Foliar phytotoxicity was evaluated on seedlings of Phaseolus vulgaris. Results: the complete oil showed considerable acute repellent and insecticide activity related to its chemical composition. The acute insecticidal activity of the fractions decreased significantly if compare with that of the whole oil , but neither significant effects on the repellent activity nor phytotoxicity on the bean leaves were observed. Conclusions: the essential oil of this eucalyptus species has considerable anti-insect properties and could be formulated as an insecticide for the control of insects of agricultural and medical significance.