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111.
112.
Williams TM Davis RW Fuiman LA Francis J Le Boeuf BJ Horning M Calambokidis J Croll DA 《Science (New York, N.Y.)》2000,288(5463):133-136
Locomotor activity by diving marine mammals is accomplished while breath-holding and often exceeds predicted aerobic capacities. Video sequences of freely diving seals and whales wearing submersible cameras reveal a behavioral strategy that improves energetic efficiency in these animals. Prolonged gliding (greater than 78% descent duration) occurred during dives exceeding 80 meters in depth. Gliding was attributed to buoyancy changes with lung compression at depth. By modifying locomotor patterns to take advantage of these physical changes, Weddell seals realized a 9.2 to 59.6% reduction in diving energetic costs. This energy-conserving strategy allows marine mammals to increase aerobic dive duration and achieve remarkable depths despite limited oxygen availability when submerged. 相似文献
113.
114.
A field study was conducted at North Platte, Nebraska in 2007–2009, imposing eight irrigation treatments, ranging from dryland to fully irrigated. Four of the eight treatments allowed for various degrees of water stress only after tasseling and silking. In 2007, corn yield ranged from 8.9 Mg ha?1 with a season total of 41 mm of irrigation water to 11.5 Mg ha?1 for the fully irrigated treatment (264 mm of irrigation water). The treatment with the greatest reduction in irrigation water after tasseling and silking (158 mm) had a mean yield of 10.9 Mg ha?1, only 0.6 Mg ha?1 less than the fully irrigated treatment. In 2009, yields ranged from 12.6 to 13.5 Mg ha?1. There were no significant yield differences between the irrigation treatments for several possible reasons: more in-season precipitation and cooler weather required less irrigation water; much of the irrigation water was applied after the most water-stress sensitive stages of tasseling and silking; and lower atmospheric demand allowed for soil water contents well below 50 % management allowed depletion (MAD) not to cause any yield losses. 相似文献
115.
Amare Haileslassie Don Peden Solomon Gebreselassie Tilahun Amede Katrien Descheemaeker 《Agricultural Systems》2009,102(1-3):33-40
Water scarcity is a major factor limiting food production. Improving Livestock Water Productivity (LWP) is one of the approaches to address those problems. LWP is defined as the ratio of livestock’s beneficial outputs and services to water depleted in their production. Increasing LWP can help achieve more production per unit of water depleted. In this study we assess the spatial variability of LWP in three farming systems (rice-based, millet-based and barley-based) of the Gumera watershed in the highlands of the Blue Nile basin, Ethiopia. We collected data on land use, livestock management and climatic variables using focused group discussions, field observation and secondary data. We estimated the water depleted by evapotranspiration (ET) and beneficial animal products and services and then calculated LWP. Our results suggest that LWP is comparable with crop water productivity at watershed scales. Variability of LWP across farming systems of the Gumera watershed was apparent and this can be explained by farmers’ livelihood strategies and prevailing biophysical conditions. In view of the results there are opportunities to improve LWP: improved feed sourcing, enhancing livestock productivity and multiple livestock use strategies can help make animal production more water productive. Attempts to improve agricultural water productivity, at system scale, must recognize differences among systems and optimize resources use by system components. 相似文献
116.
O’Brien Peter L. DeSutter Thomas M. Casey Francis X. M. 《Journal of Soils and Sediments》2019,19(3):1367-1373
Journal of Soils and Sediments - Natural degradation of petroleum hydrocarbons (PHC) is a crucial process to consider when managing contaminated soils. However, the degradation rate is dictated by... 相似文献
117.
Growth trials were conducted outdoors in the UK to determine the yield, yield components and plant architectural differences
between determinate and indeterminate Phaseolus vulgaris bean plants. F3 lines derived from crosses between ‘Prelude’, a determinate cultivar and ‘V8’, an indeterminate landrace,
were grown together with the parents and ‘Carioca’, an indeterminate landrace from Brazil. Data were recorded on flowering
date, number of nodes on main stem at flowering, plant height at maturity, number of pods/plant, number of seeds/pod, number
of seeds/plant, 100-seed weight, seed mass/plant, percentages of diseased and healthy seeds/plant. Determinate F3 lines had
significantly lower (P < 0.05) seed mass/plant, fewer pods/plant, fewer seeds/pod, fewer seeds/plant, lower harvest index, shorter stems, earlier
date of flowering, fewer nodes at flowering and fewer healthy seeds/plant than indeterminate F3 lines. However, determinate
genotypes had significantly larger (P < 0.05) pods to accommodate their larger seeds compared with indeterminate lines. A similar situation was found when the
yield and yield components of ‘V8’, ‘Prelude’ and ‘Carioca’ were evaluated; the highest seed mass/plant was given by ‘V8’
and the lowest by ‘Prelude’. Furthermore, some indeterminate genotypes with Type IV growth habit yielded significantly higher
(P < 0.05) than the high-yielding parent, ‘V8’, indicating a positive influence on seed yield by crossing different genotypes. 相似文献
118.
Francis Leo Collins 《Asia Pacific viewpoint》2006,47(2):217-234
Abstract: In recent years, international education has become a source of considerable political, academic and media debate in New Zealand. This is nowhere more the case than with regards to Auckland, the New Zealand city that has hosted the greatest number of international students. This paper focuses on the media debates around international students in Auckland with particular emphasis on the representations of the largest group of international students, those who originate from countries within the North‐East Asian region. The media representations of these students have fixed a diverse group of individuals within a singular racial identity that is known by stereotypical economic, cultural and social characteristics. As a result, these representations have further problematised the interaction between international students and the host population in Auckland while simultaneously implicating a cohort of young New Zealand citizens and permanent residents who are of similar descent within the same discourses. This process of othering the Asian student, regardless of citizenship, has consequences not simply for the practice of exporting education in this city but also for the future of a multicultural Auckland and New Zealand. 相似文献
119.
In pearl millet (Pennisetum glaucum (L.) R. Br.), single cross hybrids based largely on exotic germplasm, have found very limited adoption in drought-prone arid
regions mainly due to their inadequate adaptation to prevalent extremely harsh agro-climatic conditions. This study tested
the hypothesis that the use of restorer parents derived from adapted landrace germplasm could be an alternative strategy in
developing suitable hybrids for arid regions. Forty inbred restorer lines developed from two phenotypically diverse landraces
were used to develop hybrids evaluated in this study for their performance in five typical arid zone environments between
2003 and 2007. Inbred lines from both landrace populations differed significantly in their combining ability for biomass,
harvest index and grain and stover yields. A larger proportion of experimental hybrids, based on selected inbred lines, significantly
outperformed the commercial checks for grain and stover yields. Increase in grain and stover yields was achieved primarily
due to their higher biomass productivity, with no decline in harvest index. Choice of landrace determined the relative grain
and stover productivity of their hybrids. Phenotypic differences observed in parental landraces in tillering and panicle length
were also visible in their respective hybrids, indicating that characteristics of landrace parental populations were transmitted
in their hybrids. 相似文献
120.
Heat stress adversely affects wheat production in many regions of the world and is particularly detrimental during reproductive
development. The objective of this study was to identify novel quantitative trait loci (QTL) associated with improved heat
tolerance in wheat (Triticum aestivum L.) and to confirm previous QTL results. To accomplish this, a recombinant inbred line (RIL) population was subjected to
a three-day 38°C daytime heat stress treatment during early grain-filling. At maturity, a heat susceptibility index (HSI)
was calculated from the reduction of three main spike yield components; kernel number, total kernel weight, and single kernel
weight. The HSI, as well as temperature depression (TD) of the main spike and main flag leaf during heat stress were used
as phenotypic measures of heat tolerance. QTL analysis identified 14 QTL for HSI, with individual QTL explaining from 4.5
to 19.3% of the phenotypic variance. Seven of these QTL co-localized for both TD and HSI. At all seven loci, the allele for
a cooler flag leaf or spike temperature (up to 0.81°C) was associated with greater heat tolerance, indicated by a lower HSI.
In a comparison to previous QTL results in a RIL population utilizing the same source of heat tolerance, seven genome regions
for heat tolerance were consistently detected across populations. The genetic effect of combining three of these QTL, located
on chromosomes 1B, 5A, and 6D, demonstrate the potential benefit of selecting for multiple heat tolerance alleles simultaneously.
The genome regions identified in this study serve as potential target regions for fine-mapping and development of molecular
markers for more rapid development of heat tolerant germplasm. 相似文献