Two contrasting barley (Hordeum vulgare L.) cultivars: Kepin No.7 (salt sensitive), and Jian 4 (salt tolerant) were grown hydroponically to investigate the microdistribution of mineral ions in roots as affected by sil...Two contrasting barley (Hordeum vulgare L.) cultivars: Kepin No.7 (salt sensitive), and Jian 4 (salt tolerant) were grown hydroponically to investigate the microdistribution of mineral ions in roots as affected by silicon (Si) with respect to salt tolerance. The experiment was undertaken consisting of two treatments with 3 replicates: (i) 120 mmol@L?1 NaCl alone (referred to as Si(NaCl+), (ii) 120 mmol@L?1 NaCl + 1.0 mmol@L?1 Si (as potassium silicate) (referred to as Si+NaCl+). Plant root tips were harvested for microanalysis using an energy dispersive X-ray microanalyzer (EDX) 30 d after transplanting. Higher Cl and Na X-ray peaks were recorded in the root epidermal, cortical and stelar cells of roots for the treatment Si(NaCl+ with the majorities of Na and Cl being accumulated in epidermal and cortical cells, while relatively low K peaks were observed regardless of the barley cultivars used. By contrast, considerably higher K peaks were detected in the epidermal, cortical and stelar cells of the roots for the treatment Si+NaCl+, but lower Cl and Na peaks were also observed for this treatment with both Na and Cl ions being evenly distributed in the epidermal, cortical and stelar cells. These findings directly support our previous finding, which showed that Si depressed the uptake of sodium but enhanced the uptake of potassium by salt-stressed barley. We believe that one of the possible mechanisms involved in Si-enhancement of salt tolerance in barley is attributed to the Si-induced changes in the uptake and microdistribution of mineral ions in plants.展开更多
Physical Habitat characterization of black flies was performed in the Tafna Basin of Algeria, based primarily on stream size, substrate, and aquatic and riparian vegetation. A total of 143 samples were taken between A...Physical Habitat characterization of black flies was performed in the Tafna Basin of Algeria, based primarily on stream size, substrate, and aquatic and riparian vegetation. A total of 143 samples were taken between April and October 2009 at 11 sampling sites in the Tafna catchment. Dams exerted an effect through a slowdown of flow and sedimentation of fine particles, eliminating coarse microhabitats favorable for black flies. Stream and substrate characteristics are key parameters that determined the microhabitats of the species. Of 10 species considered, four were widely present with significant plasticity for the stream and substrate. Four other species were more closely associated with faster streams and eroded substrate. A greater rheophilic tendency was found for Simulium bezzii (Corti), Simulium sergenti Edwards, Simulium quadrifila Grenier, Faure and Laurent and Simulium galloprovinciale Giudicelli, which represents a new record for Algeria.展开更多
基金This work was jointly supported by the National Natural Science Foundation of China (Grant Nos.39470424 & 39770441) and the International Foundation for Science. The authors are grateful to Dr. B. Forster of the Scottish Crop Research Institute, Dundee
文摘Two contrasting barley (Hordeum vulgare L.) cultivars: Kepin No.7 (salt sensitive), and Jian 4 (salt tolerant) were grown hydroponically to investigate the microdistribution of mineral ions in roots as affected by silicon (Si) with respect to salt tolerance. The experiment was undertaken consisting of two treatments with 3 replicates: (i) 120 mmol@L?1 NaCl alone (referred to as Si(NaCl+), (ii) 120 mmol@L?1 NaCl + 1.0 mmol@L?1 Si (as potassium silicate) (referred to as Si+NaCl+). Plant root tips were harvested for microanalysis using an energy dispersive X-ray microanalyzer (EDX) 30 d after transplanting. Higher Cl and Na X-ray peaks were recorded in the root epidermal, cortical and stelar cells of roots for the treatment Si(NaCl+ with the majorities of Na and Cl being accumulated in epidermal and cortical cells, while relatively low K peaks were observed regardless of the barley cultivars used. By contrast, considerably higher K peaks were detected in the epidermal, cortical and stelar cells of the roots for the treatment Si+NaCl+, but lower Cl and Na peaks were also observed for this treatment with both Na and Cl ions being evenly distributed in the epidermal, cortical and stelar cells. These findings directly support our previous finding, which showed that Si depressed the uptake of sodium but enhanced the uptake of potassium by salt-stressed barley. We believe that one of the possible mechanisms involved in Si-enhancement of salt tolerance in barley is attributed to the Si-induced changes in the uptake and microdistribution of mineral ions in plants.
文摘Physical Habitat characterization of black flies was performed in the Tafna Basin of Algeria, based primarily on stream size, substrate, and aquatic and riparian vegetation. A total of 143 samples were taken between April and October 2009 at 11 sampling sites in the Tafna catchment. Dams exerted an effect through a slowdown of flow and sedimentation of fine particles, eliminating coarse microhabitats favorable for black flies. Stream and substrate characteristics are key parameters that determined the microhabitats of the species. Of 10 species considered, four were widely present with significant plasticity for the stream and substrate. Four other species were more closely associated with faster streams and eroded substrate. A greater rheophilic tendency was found for Simulium bezzii (Corti), Simulium sergenti Edwards, Simulium quadrifila Grenier, Faure and Laurent and Simulium galloprovinciale Giudicelli, which represents a new record for Algeria.
