Effect of a topical treatment with juvenile hormone analogues on dominance, ovarian development and corpora allata size in Bombus terrestris workers

Juvenile hormone analogues (JHAs) are insecticides that mimic the effect of juvenile hormone (JH), one of the main regulatory hormones in insects. Negative effects of JHAs on preimaginal stages are well known, while little is known of their effects on adults. In this study we assessed the effect of three JHAs on newly emerged workers of Bombus terrestris L. kept in queenless groups. Reproductive dominance status, oocyte length and corpora allata volume were assessed 4 and 7 days after treatment. Contrary to expectations, none of the treatments had a significant stimulating effect on ovarian development in reproductive dominant workers. Conversely, most treatments caused a significant reduction in oocyte size and in corpora allata volumes of seven-day-old reproductive subordinates, indicating a feedback loop of exogenous JHAs on these glands. The study suggests that besides JH, multiple factors influence worker ovarian activity, which makes it difficult to predict the effect of the insecticides in wild colonies.Fil: Bortolotti, Laura. Consiglio Per la Ricerca In Agricoltura E L' Analisi del L' Economía Agraria. Centro de Ricerca Per Le Produzioni Foraggere E Lattier-casearie; ItaliaFil: Bogo, Gherardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; ArgentinaFil: Poscic, Filip. Institute For Adriatic Crops And Karst Reclamation; CroaciaFil: Duchateau, Marie José. University of Utrecht; Países Bajo

Changes in Physiological and Agronomical Parameters of Barley (Hordeum vulgare) Exposed to Cerium and Titanium Dioxide Nanoparticles

The aims of our experiment were to evaluate the uptake and translocation of cerium and titaniumoxide nanoparticles and to verify their effects on the growth cycle of barley (Hordeum vulgare L.). Barley plants were grown to physiological maturity in soil enriched with either 0, 500 or 1000 mg kg1 cerium oxide nanoparticles (nCeO2) or titanium oxide nanoparticles (nTiO2) and their combination. The growth cycle of nCeO2 and nTiO2 treated plants was about 10 days longer than the controls. In nCeO2 treated plants the number of tillers, leaf area and the number of spikes per plant were reduced respectively by 35.5%, 28.3% and 30% (p \ua4 0.05). nTiO2 stimulated plant growth and compensated for the adverse effects of nCeO2. Concentrations of Ce and Ti in aboveground plant fractions were minute. The fate of nanomaterials within the plant tissues was different. Crystalline nTiO2 aggregates were detected within the leaf tissues of barley, whereas nCeO2 was not present in the form of nanoclusters

Independent variation in copper tolerance and copper accumulation among crop species and varieties

Copper (Cu) locally contaminates soils and might negatively affect growth and yield of crops. A better understanding of plant copper tolerance and accumulation is needed in order to breed more Cu-tolerant or Cu-efficient crops. Cu tolerance was evaluated in different varieties of seven species (Brassica carinata, B. juncea, B. napus, Cynara cardunculus, Helianthus annuus, Nicotiana tabacum and Raphanus sativus) exposed to a series of CuSO4 concentrations (0.1\u20138 \u3bcM CuSO4) in the nutrient solution. Plants were further exposed to 0.1 \u3bcM CuSO4 and to their variety-specific concentrations that reduced root growth to 50% of the maximum rate (EC50). Among all the varieties of all the species the EC50 varied from 0.7 up to 3.1 \u3bcM Cu. B. carinata was significantly more Cusensitive than the other species, which were not significantly different among each other, and B. carinata and H. annuus accommodated significant intra-specific, inter-varietal variation. There were significant differences between species in Cu uptake efficiency and nutrient status. When under EC50 exposure, all the Brassicaceae, except B. carinata, maintained low Cu concentrations in shoots, whereas the other species and B. carinata exhibited significantly increased shoot Cu concentrations, compared to the control. There was no apparent relationship between Cu tolerance and Cu accumulation in roots and shoots, suggesting that the observed variation in tolerance, both between and within species, is not explained by differential exclusion capacity. Discriminant analysis and treatment comparisons suggest possible contribution of lignin, saturated fatty acids, manganese (Mn) and zinc (Zn) in tolerance to high Cu concentrations in shoot