排序方式: 共有36条查询结果,搜索用时 31 毫秒
31.
Photosynthesis was characterized for the unicellular green alga Coccomyxa sp., grown at low inorganic carbon (Ci) concentrations, and compared with Chlamydomonas reinhardtii, which had been grown so that the CO2 concentrating mechanism (CCM) was expressed, and with protoplasts isolated from the C3 plant barley (Hordeum vulgare). Chlamydomonas had a significantly higher Ci-use efficiency of photosynthesis, with an initial slope of the Ci-response curve of 0.7 mol(gChl)−1 h−1 mmol Cim−3)−1, as compared to 0.3 and 0.23 mol(gChl)−1 h−1 (mmol Cim−3)−1 for Coccomyxa and barley, respectively. The affinity for Ci was also higher in Chlamydomonas, as the half maximum rate of photosynthesis [K0.5 (Ci)] was reached at 0.18 mol m−3, as compared to 0.30 and 0.45 mol m−3 for Coccomyxa and barley, respectively. Ethoxyzolamide (EZ), an inhibitor of the enzyme carbonic anhydrase (CA) and the CCM, caused a 17-fold decrease in the initial slope of the photosynthetic Cj-response curve in Chlamydomonas, but only a 1.5- to two-fold decrease in Coccomyxa and barley. The photosynthetic light-response curve showed further similarities between barley and Coccomyxa. The rate of bending of the curve, described by the convexity parameter, was 0.99 (sharp bending) and 0.81–0.83 (gradual bending) for cells grown under low and high light, respectively. In contrast, the maximum convexity of Chlamydomonas was 0.85. The intrinsically lower convexity of Chlamydomonas is suggested to result from the diversion of electron transport from carbon fixation to the CCM. Taken together, these results suggest that Coccomyxa does not possess a CCM and due to this apparent lack of a CCM, we propose that Coccomyxa is a better cell model system for studying C3 plant photosynthesis than many algae currently used. 相似文献
32.
Genetic variation and heavy metal tolerance in the ectomycorrhizal basidiomycete Suillus luteus 总被引:2,自引:1,他引:1
JAN V. COLPAERT PHILIPPE VANDENKOORNHUYSE KRISTIN ADRIAENSEN & JACO VANGRONSVELD 《The New phytologist》2000,147(2):367-379
Twenty-one isolates of the ectomycorrhizal fungus Suillus luteus were screened for their tolerance to the heavy metals Zn, Cd, Cu and Ni, measured as inhibition of radial growth and biomass production. Two populations from even-aged pine stands were investigated: 10 isolates were obtained from an area polluted with high levels of Zn, Cd and Cu, and 11 isolates were obtained from a control population located in a nearby unpolluted area. RFLP patterns of the internal transcribed spacer region of the isolates confirmed the morphological identification of the carpophores. All isolates were maintained on basic medium without elevated metals to avoid phenotypically acquired metal tolerance. The in vitro Zn and Cd tolerance of the S. luteus isolates from the polluted habitat were significantly higher than the tolerances measured in the isolates from the nonpolluted site. This observation suggests that the elevated soil metal concentrations might be responsible for the evolution of adaptive Zn and Cd tolerance. Tolerance was maintained in an isolate not exposed to elevated metals for 3 yr. The two S. luteus populations did not differ in tolerance to Cu and Ni. The mechanisms for the adaptive Zn and Cd tolerance are not identical as there was no correlation between response to the two metals; the most Zn-tolerant isolate was the most sensitive for Cd in the metal-tolerant population. Zinc did not accumulate in basidiocarp tissue, whereas Cd levels in basidiocarps were significantly higher in the population on the polluted site. Inter-simple sequence-repeat fingerprints showed that 90% of the isolates were from different individuals. The genetic variation in the population from the unpolluted site was considerably larger than that observed at the polluted site. 相似文献
33.
Using Statistical Population Reconstruction to Estimate Demographic Trends in Small Game Populations
KRISTIN BROMS JOHN R. SKALSKI JOSHUA J. MILLSPAUGH CHRISTIAN A. HAGEN JOHN H. SCHULZ 《The Journal of wildlife management》2010,74(2):310-317
ABSTRACT Statistical population reconstruction offers a robust approach to demographic assessment for harvested populations, but current methods are restricted to big-game species with multiple age classes. We extended this approach to small game and analyzed 14 years of age-at-harvest data for greater sage-grouse (Centrocercus urophasianus) in Oregon, USA, in conjunction with radiotelemetry data to reconstruct annual abundance levels, recruitment, and natural survival probabilities. Abundance estimates ranged from a low of 26,236 in 1995 to a high of 39,492 in 2004. Annual abundance estimates for adult males were correlated with a spring lek count index (r = 0.849, P < 0.029). We estimated the average annual harvest mortality for the population to be 0.028, ranging from 0.021 to 0.031 across years. We estimated the probability of natural survival of adult females to be 0.818 ( = 0.052), somewhat higher than that of adult males (Ŝ = 0.609, = 0.163). Our precision in reconstructing the population was hampered by low harvest rates and the few birds tagged in the radiotelemetry investigations. Despite these issues, our analysis illustrates how modern statistical reconstruction procedures offer a flexible framework for demographic assessment using commonly collected data. This approach offers a useful alternative to small-game indices and would be most appropriate for species with 5 or more years of age-at-harvest data and moderate-to-heavy harvest rates. 相似文献
34.
KRISTIN DOWELL 《American anthropologist》2006,108(2):376-384
For 12 days in May 2005, the Museum of Modern Art (MoMA) in New York and the Smithsonian's National Museum of the American Indian (NMAI), as well as several other screening venues in Washington, D.C., hosted a group of renowned indigenous filmmakers from around the globe for the groundbreaking film showcase, "First Nations/First Features: A Showcase of World Indigenous Film and Media." This film showcase highlighted the innovative ways in which indigenous filmmakers draw on indigenous storytelling practices to create cinematic visions that honor their long-standing indigenous cultural worlds while reaching local and world audiences. In this essay, I highlight the onscreen impact through an analysis of several films featured in First Nations/First Features, as well as the offscreen impact emphasizing how the indigenous directors used this opportunity to strengthen social networks and share experience in this industry, which may develop into future collaborative film projects. 相似文献
35.
36.
1. Invasive zebra ( Dreissena polymorpha ) and quagga mussels ( Dreissena bugensis ) have become widespread throughout the Great Lakes basin. However, some types of Great Lakes coastal wetlands may be unsuitable for Dreissena invasion.
2. To test this observation, artificial substrata were placed in wetlands (with emergent vegetation) and in adjacent open water (without emergent vegetation) habitats in two types of Great Lakes coastal ecosystems: drowned river mouth (DRM) and coastal fringing systems. Wetlands in DRM systems generally have deep organic sediment and limited water movement, whereas coastal fringing wetlands generally have low to moderate amounts of organic sediment and intense wind and wave action.
3. We did not find a significant difference in Dreissena colonisation between wetlands and adjacent open water habitat in fringing systems. However, Dreissena colonisation was significantly lower in DRM wetlands than in the adjacent open water. We also found significantly lower survival in DRM wetlands than adjacent open water habitats, whereas survival did not differ significantly in coastal fringing wetlands and the adjacent open water.
4. Our results suggest that vulnerability to Dreissena invasion varied among wetland types with DRM wetlands being less suitable than fringing wetlands. We suggest that colonisation and survival of Dreissena is lower in wetlands with deep organic sediment and less turbulent water. 相似文献
2. To test this observation, artificial substrata were placed in wetlands (with emergent vegetation) and in adjacent open water (without emergent vegetation) habitats in two types of Great Lakes coastal ecosystems: drowned river mouth (DRM) and coastal fringing systems. Wetlands in DRM systems generally have deep organic sediment and limited water movement, whereas coastal fringing wetlands generally have low to moderate amounts of organic sediment and intense wind and wave action.
3. We did not find a significant difference in Dreissena colonisation between wetlands and adjacent open water habitat in fringing systems. However, Dreissena colonisation was significantly lower in DRM wetlands than in the adjacent open water. We also found significantly lower survival in DRM wetlands than adjacent open water habitats, whereas survival did not differ significantly in coastal fringing wetlands and the adjacent open water.
4. Our results suggest that vulnerability to Dreissena invasion varied among wetland types with DRM wetlands being less suitable than fringing wetlands. We suggest that colonisation and survival of Dreissena is lower in wetlands with deep organic sediment and less turbulent water. 相似文献