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91.
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Ecosystem experiments 总被引:1,自引:0,他引:1
Carpenter SR Chisholm SW Krebs CJ Schindler DW Wright RF 《Science (New York, N.Y.)》1995,269(5222):324-327
Experimental manipulations of entire ecosystems have been conducted in lakes, catchments, streams, and open terrestrial and marine environments. Experiments have addressed applied problems of ecosystem management and complex responses of communities and ecosystems to perturbations. In the course of some experiments, environmental indicators and models have been developed and tested. Surprising results with implications for ecological understanding and management are common. 相似文献
94.
Wright AD Sampson MB Neuffer MG Michalczuk L Slovin JP Cohen JD 《Science (New York, N.Y.)》1991,254(5034):998-1000
The maize mutant orange pericarp is a tryptophan auxotroph, which results from mutation of two unlinked loci of tryptophan synthase B. This mutant was used to test the hypothesis that tryptophan is the precursor to the plant hormone indole-3-acetic acid (IAA). Total IAA in aseptically grown mutant seedlings was 50 times greater than in normal seedlings. In mutant seedlings grown on media containing stable isotopelabeled precursors, IAA was more enriched than was tryptophan. No incorporation of label into IAA from tryptophan could be detected. These results establish that IAA can be produced de novo without tryptophan as an intermediate. 相似文献
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High-performance liquid chromatography provides direct evidence for substantial removal of naturally occurring specific free amino acids during a single passage of water through the mantle cavity of mussels. This occurs during the few seconds required for passage of the water across the gill, and removal proceeds unabated at ambient substrate concentrations as low as 38 nanomoles per liter. 相似文献
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Application of a comprehensive wave climate program to seven major deltas indicates that deltaic configurations and coastal landform combinations depend to a considerable degree on the wave power adjacent to the shore and on the river discharge relative to wave forces. Nearshore wave power is not correlative with deepwater wave power but, owing to frictional attenuation, is a function of the subaqueous slope. The subaqueous slope, in turn, depends partially on the slope and width of the continental shelf but primarily on the rate at which the river can supply sediments to the nearshore zone. River-dominated configurations result only when the river is able to build flat offshore profiles, which reduce nearshore wave power; where the subaqueous slope is steep, waves reach the shore comparatively undiminished and wave-built forms prevail. 相似文献
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Uhlmann WR Bennett R Botkin JR Botstein D Boughman JA Chakravarti A Clayton EW Kahn J Koenig B Murray TH Olson MV Rowley J Terry S Valle D 《Science (New York, N.Y.)》2003,299(5612):1515; author reply 1515