RESUMO
Leaf-cutter ant species (Atta spp.) are key pests of cultivated crops in the Neotropics, and recent studies have demonstrated that workers of Atta spp., particularly of Atta sexdens rubropilosa, exhibit aggressive behavior among nestmates when in contact with the sesquiterpene beta-eudesmol, found in leaves of Eucalyptus maculata. However, the underlying mechanism sparking this behavior pattern has yet to be investigated. This work aimed to elucidate the mechanism by which this substance elicits aggression in workers of A. sexdens rubropilosa. The results, thus obtained, showed that beta-eudesmol is able to modify the chemical composition of the workers cuticle, impairing nestmate recognition, triggering alarm behavior and leading to nestmate aggression.
Assuntos
Comunicação Animal , Formigas/efeitos dos fármacos , Sesquiterpenos de Eudesmano/farmacologia , Agressão/efeitos dos fármacos , Animais , Formigas/metabolismo , Formigas/fisiologia , Feromônios/metabolismo , Feromônios/fisiologia , Sesquiterpenos de Eudesmano/metabolismo , Estimulação QuímicaRESUMO
Aluminum (Al) tolerance mechanisms in crop plants have been extensively researched, but our understanding of the physiological mechanisms underlying Al tolerance in trees is still limited. To investigate Al tolerance in eucalypts, seedlings of six species (Eucalyptus globulus Labill., Eucalyptus urophylla S.T. Blake, Eucalyptus dunnii Maiden, Eucalyptus saligna Sm., Eucalyptus cloeziana F. J. Muell. and Eucalyptus grandis w. Hill ex Maiden) and seedlings of six clones of Eucalyptus species were grown for 10 days in nutrient solutions containing Al concentrations varying from 0 to 2.5 microM (0 to 648 microM Al3+ activities). Root elongation of most species was inhibited only by high Al3+ activities. Low to intermediate Al3+ activities were beneficial to root elongation of all species and clones. Among the species tested, E. globulus and E. urophylla were more tolerant to Al toxicity, whereas E. grandis and E. cloeziana were more susceptible to Al-induced damage. Although E. globulus seedlings were tolerant to Al toxicity, they were highly sensitive to lanthanum (La), indicating that the tolerance mechanism is specific for Al. Fine roots accumulated more Al and their elongation was inhibited more than that of thick roots. In E. globulus, accumulation of Al in root tips increased linearly with increasing Al concentration in the nutrient solution. The majority of Al taken up was retained in the root system, and the small amounts of Al translocated to the shoot system were found mainly in older leaves. No more than 60% of the Al in the thick root tip was in an exchangeable form in the apoplast that could be removed by sequential citrate rinses. Gas chromatography/mass spectrometry and ion chromatography analyses indicated that root exposure to Al led to a greater than 200% increase in malic acid concentration in the root tips of all eucalypt species. The increase in malate concentration in response to Al treatment correlated with the degree of Al tolerance of the species. A small increase in citric acid concentration was also observed in all species, but there were no consistent changes in the concentrations of other organic acids in response to Al treatment. In all eucalypt species, Al treatment induced the secretion of citric and malic acid in root exudates, but no trend with respect to Al tolerance was observed. Thus, although malate and citrate exudation by roots may partially account for the overall high Al tolerance of these eucalypt species, it appears that tolerance is mainly derived from the internal detoxification of Al by complexation with malic acid.
Assuntos
Alumínio/farmacologia , Eucalyptus/efeitos dos fármacos , Árvores/efeitos dos fármacos , Alumínio/análise , Ácido Cítrico/metabolismo , Eucalyptus/fisiologia , Coifa/química , Raízes de Plantas/química , Raízes de Plantas/efeitos dos fármacos , Raízes de Plantas/fisiologia , Brotos de Planta/química , Árvores/fisiologiaRESUMO
In wind-tunnel bioassays, dispensers loaded with 1 microg of the synthetic major component (3E,8Z, 11Z)-3,8,11-tetradecatrienyl acetate (TDTA) of the sex pheromone emitted by Tuta absoluta (Meyrick) females were found to be highly attractive to conspecific males. Field experiments were conducted to evaluate the efficacy of five trap designs. The best trap, baited with 100 microg of the synthetic sex pheromone caught on average 1,200 males per trap per night, while those baited with virgin females caught only 201 males. The male response to this pheromone is restricted to the same early-morning time window during which females exhibit calling behavior. The high biological activity of the synthetic pheromone suggests that it could be useful for pest monitoring and in mating disruption.
Assuntos
Acetatos/farmacologia , Álcoois Graxos/farmacologia , Mariposas/fisiologia , Atrativos Sexuais/farmacologia , Animais , Bioensaio , Feminino , Masculino , Controle de Pragas , Dinâmica Populacional , Comportamento Sexual Animal , OlfatoRESUMO
In order to evaluate the chromium contamination from tannery discharges into rivers in the State of Minas Gerais, Brazil, samples of fluvial sediment, vegetation and fish were collected and submitted to chemical analysis. The chromium content in the samples was measured by atomic absorption spectrophotometry. Metal inputs were related to effluent discharges into the rivers. High concentrations of chromium were found in samples when compared with controls. Sediment investigations indicated strong enrichment and high geoaccumulation indices, while chromium concentrations in the analyzed vegetation were higher than those normally found in these materials. Chromium levels in fish exceeded 35 times the Brazilian recommendation value for human intake.