Physiological effects of buthidazole on Zea mays L., Amaratithus retroflexus L., Medicago sativa L. and Agropyron repens(L.) Beauv.*     

KRITON K. HATZIOS  DONALD PENNER 《Weed Research》1979,19(6):371-376

Buthidazole (3-[5-(1,1-dimethylethyl)-1,3.4-thiadiazol-2-yl]-4-hydroxy-l-methyl-2-imidazolidinone) at concentrations of 10^?6-10^?4M did not affect germination of corn (Zea mays L.,‘Pioneer 3780’), redroot pigweed (Amaranlhus retroflexus L.), alfalfa (Medicago saliva L., ‘Vernal’), and quackgrass (Agropyron repens(L.) Beauv.) seeds. Stressing the seeds obtained from mature corn plants treated either pre-emergence or pre- plant incorporated with buthidazole at several rates by accelerated ageing and cold treatments further indicated that this herbicide did not affect germination. Total photosynthesis and dark respiration of corn plants 12 days after pre-emergence application and of redroot pigweed, alfalfa, and quackgrass plants after postemergence application of buthidazole at several rates were measured with an infrared CO₂ analyser. The results suggested that buthidazole was a rapid inhibitor of photosynthesis of the sensitive redroot pigweed and quackgrass plants, with less effect on corn and alfalfa. Buthidazole did not affect respiration of the examined species except for a transitory increase in corn and alfalfa 12 days after pre-emergence or 4 h after postemergence treatment with buthidazole at 0.56 or 1.12 and 2.24 kg/ha, respectively. A long-term inhibition of quackgrass respiration 96 h after treatment with buthidazole at 1.12 and 224 kg/ha was also evident.  相似文献   

Marine and freshwater climatic factors affecting interannual variation in the timing of return migration to fresh water of sockeye salmon (Oncorhynchus nerka)   总被引：1，自引：0，他引：1  

SAYRE HODGSON  THOMAS P. QUINN  RAY HILBORN  ROBERT C. FRANCIS  DONALD E. ROGERS 《Fisheries Oceanography》2006,15(1):1-24

Interannual variation in the timing of the return migration to fresh water of adult sockeye salmon, Oncorhynchus nerka, from 46 populations throughout the species North American range was examined in a broad analysis of how timing patterns are affected by marine and freshwater conditions. Migration timing data (measured at various points along the migration, including just prior to freshwater entry, just after freshwater entry, and near the spawning grounds) were examined for correlations with sea‐surface temperatures (SST) prior to migration and to freshwater temperatures and flows during migration. Following a spring–summer period with warm SST, populations from southwestern Alaska tended to return early, Fraser River populations returned late, and populations from other regions showed no consistent patterns. Similarities between interannual timing of both nearby and distant populations indicated the presence of common or coincidental influences on timing. When riverine conditions related to timing, high flows and low temperatures were associated with late migrations, low flows and high temperatures were associated with early migrations. However, even counting stations at upriver locations showed correlations with SST. Notwithstanding some inconsistencies among the many populations examined and the indirect nature of the inferences, the results supported the hypotheses that (i) interannual variations in salmon distributions at sea reflect temperature conditions, and (ii) the date when salmon initiate homeward migration is a population‐specific trait, largely unaffected by the fish's location at sea.  相似文献   

'Aquaculture and Water Resource Management' An International Symposium held at the University of Stirling, 21-25 June 1994     

LIAM A KELLY  MALCOLM C M BEVERIDGE  DONALD J BAIRD  JAMES F MUIR 《Aquaculture Research》1995,26(8):513-513

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Evaluating Alternative Regional Planning Models: Comment     

DONALD R. GRIMES  GEORGE A. FULTON  MARC A. BONARDELLI 《Growth and change》1992,23(4):516-520

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Transitions of Poverty Amidst Employment Growth: Two Nonmetro case studies     

DONALD K. LARSON 《Growth and change》1989,20(2):19-34

ABSTRACT The theory behind employment growth as a strategy for lessening the poverty problem is based on a premise that job opportunities are inadequate. But during rapid employment growth in some nonmetropolitan areas of Kentucky and Georgia the effect on poverty has been limited. A large majority of poor households have no potential to leave poverty via employment since age, health, and other limiting factors among household members restrict entry into the work force. Also, for some the condition of being poor resulted not because they had never worked, but because they tended to have worked at marginal, low-wage jobs. Meanwhile, some jobs went unfilled because employers could not find persons who could meet the right requirements. This study shows that in these two areas, expanding employment opportunities did not significantly reduce the poverty problem. As the literature addressing the issue of the effects of employment growth on poverty is inconclusive and sometimes contradictory, clarification of how employment gains are distributed among local residents is essential.  相似文献