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531.
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Polioviruses could not be detected in about 50% of sewage samples despite routine administration of live attenuated poliovirus vaccine to the infant population. 相似文献
533.
Nectar standing crops in flowers within an individual plant are often highly variable. This variability may be a by-product
of the foraging activity of insect pollinators. Alternatively, plants may be selected to produce highly variable rewards to
reduce consecutive visitation by risk-averse pollinators, thus diminishing within-plant pollen transfer. This study evaluated
the roles of pollinator control vs. plant control over nectar variability in the bee-pollinated shrub Rosmarinus officinalis L. (Lamiaceae). We sampled nectar production, standing crop and pollinator visits in three shrubs of one population over
17 days during one blooming season. Nectar production rates were highly variable (CV = 1.48), and increased after rainy days.
Nectar standing crops were even more variable (CV = 2.16), decreased with increasing temperatures, and increased with time
since the last rain. Pollinator visit rates decreased with variability in nectar standing crops, increased with flower number
per shrub, and were unaffected by variability in nectar production rates. Repeated sampling of marked flowers revealed no
correlation between their nectar standing crops and production rates. These findings support the role of reward variance in
reducing pollinator visits, but suggest that plants are not in complete control of this variability. Rather, plant-generated
variability can be modified by intensive foraging activity of pollinators. Such pollinator control over nectar variability
is likely to reduce the selective advantage of plant-generated reward variation.
Handling Editor: Neal Williams. 相似文献
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Isolation and identification of pathogenic microorganisms at wastewater-irrigated fields: ratios in air and wastewater. 总被引:4,自引:2,他引:2 下载免费PDF全文
B Teltsch S Kedmi L Bonnet Y Borenzstajn-Rotem E Katzenelson 《Applied microbiology》1980,39(6):1183-1190
Samples of air and corresponding wastewater samples were taken at wastewater spray-irrigated fields. The concentrations of salmonellae and enteroviruses present in these samples were determined and compared with those of coliforms, and the ratios between them were calculated. The most common Salmonella serotype in the air was Salmonella ohio, whereas in the wastewater, Salmonella anatum was the most common. Enteroviruses isolated and identified were poliovirus, echovirus, and coxsackievirus type B. From the ratios of salmonellas to coliforms and enteroviruses to coliforms in the air, as compared to these ratios in the wastewater, it was concluded that the suitability of coliforms as an indication of airborne contamination caused by spray irrigation is questionable. 相似文献