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151.
Yeongseon Park Yuseob Kim 《Evolution; international journal of organic evolution》2019,73(8):1564-1577
Temporally varying selection is known to maintain genetic polymorphism under certain restricted conditions. However, if part of a population can escape from selective pressure, a condition called the “storage effect” is produced, which greatly promotes balanced polymorphism. We investigate whether seasonally fluctuating selection can maintain polymorphism at multiple loci, if cyclically fluctuating selection is not acting on a subpopulation called a “refuge.” A phenotype with a seasonally oscillating optimum is determined by alleles at multiple sites, across which the effects of mutations on phenotype are distributed randomly. This model resulted in long‐term polymorphism at multiple sites, during which allele frequencies oscillate heavily, greatly increasing the level of nonneutral polymorphism. The level of polymorphism at linked neutral sites was either higher or lower than expected for unlinked neutral loci. Overall, these results suggest that for a protein‐coding sequence, the nonsynonymous‐to‐synonymous ratio of polymorphism may exceed one. In addition, under randomly perturbed environmental oscillation, different sets of sites may take turns harboring long‐term polymorphism, thus making trans‐species polymorphism (which has been predicted as a classical signature of balancing selection) less likely. 相似文献
152.
153.
酚酸类物质的抑草效应分析 总被引:12,自引:2,他引:12
运用正交旋转回归试验设计分析5种常见的化感物质替代物水饧酸、对羟基苯甲酸、肉桂酸、香草酸和阿魏酸对田间伴生杂草稗草的抑制效应.结果表明,肉桂酸对稗草根长抑制率的影响最显著。其关系函数的二次项系数为-6.18,达极显著水平,水杨酸、对羟基苯甲酸和阿魏酸对稗草根长的抑制效应趋势与肉桂酸相同,效应曲线均为“n”形抛物线;而香草酸的效应曲线则为“U”形抛物线.当水饧酸、对羟基苯甲酸、肉桂酸、香草酸和阿魏酸浓度水平分别为0.06、0.60、0.24、0.02和0.02mmol·L^-1时,混合物对稗草根长的抑制率最大,达到78.65%。 相似文献
154.
It has been reported that flashing light enhances microalgal biomass productivity and overall photosynthetic efficiency. The
algal growth kinetics and oxygen production rates under flashing light with various flashing frequencies (5 Hz-37 kHz) were
compared with those under equivalent continuous light in photobioreactors. A positive flashing light effect was observed with
flashing frequencies over 1 kHz. The oxygen production rate under conditions of flashing light was slightly higher than that
under continuous light. The cells under the high frequency flashing light were also observed to be healthier than those under
continuous light, particularly at higher cell concentrations. When 37 kHz flashing light was applied to an LED-based photobioreactor,
the cell concentration was higher than that obtained under continuous light by about 20%. Flashing light may be a reasonable
solution to overcome mutual shading, particularly in high-density algal cultures. 相似文献
155.
Fei‐Xue Fu Mark E. Warner Yaohong Zhang Yuanyuan Feng David A. Hutchins 《Journal of phycology》2007,43(3):485-496
Little is known about the combined impacts of future CO2 and temperature increases on the growth and physiology of marine picocyanobacteria. We incubated Synechococcus and Prochlorococcus under present‐day (380 ppm) or predicted year‐2100 CO2 levels (750 ppm), and under normal versus elevated temperatures (+4°C) in semicontinuous cultures. Increased temperature stimulated the cell division rates of Synechococcus but not Prochlorococcus. Doubled CO2 combined with elevated temperature increased maximum chl a–normalized photosynthetic rates of Synechococcus four times relative to controls. Temperature also altered other photosynthetic parameters (α, Φmax, Ek, and ) in Synechococcus, but these changes were not observed for Prochlorococcus. Both increased CO2 and temperature raised the phycobilin and chl a content of Synechococcus, while only elevated temperature increased divinyl chl a in Prochlorococcus. Cellular carbon (C) and nitrogen (N) quotas, but not phosphorus (P) quotas, increased with elevated CO2 in Synechococcus, leading to ~20% higher C:P and N:P ratios. In contrast, Prochlorococcus elemental composition remained unaffected by CO2, but cell volume and elemental quotas doubled with increasing temperature while maintaining constant stoichiometry. Synechococcus showed a much greater response to CO2 and temperature increases for most parameters measured, compared with Prochlorococcus. Our results suggest that global change could influence the dominance of Synechococcus and Prochlorococcus ecotypes, with likely effects on oligotrophic food‐web structure. However, individual picocyanobacteria strains may respond quite differently to future CO2 and temperature increases, and caution is needed when generalizing their responses to global change in the ocean. 相似文献
156.
Joan Thiesen Torben S. Christensen Thomas G. Kristensen Rikke D. Andersen Brit Brunoe Trine K. Gregersen Mikkel Thrane Bo P. Weidema 《The International Journal of Life Cycle Assessment》2008,13(2):104-114
Goal, Scope and Background Traditionally, comparative life cycle assessments (LCA) have not considered rebound effects, for instance in case of significant
price differences among the compared products. No justifications have been made for this delimitation in scope. This article
shows that price differences and the consequent effects of marginal consumer expenditure may influence the conclusions of
comparative LCA significantly. We also show that considerations about rebound effects of price differences can be included
in LCAs.
Methods The direct rebound effect of a price difference is marginal consumption. Based on statistical data on private consumption
in different income groups (Statistics Denmark 2005a, 2005b), the present article provides an estimate of how an average Danish
household will spend an additional 1 DKK for further consumer goods, when the household has gained money from choosing a cheaper
product alternative. The approach is to use marginal income changes and the following changes in consumption patterns as an
expression for marginal consumption. Secondly, the environmental impact potentials related to this marginal consumption are
estimated by the use of environmental impact intensity data from an IO-LCA database (Weidema et al. 2005). Finally, it is
discussed whether, and in which ways the conclusions of comparative LCAs can be affected by including the price difference
between product alternatives. This is elucidated in a case study of a comparative LCA screening of two different kinds of
Danish cheese products (Fricke et al. 2004).
Results Car purchase and driving, use and maintenance of dwelling, clothing purchase and insurance constitutes the largest percentages
of the marginal consumption. In a case study of two cheeses, the including the impact potentials related to the price difference
results in significant changes in the total impact potentials. Considering the relatively small price difference of the two
products, it is likely also to have a significant influence on the results of comparative LCAs more generally.
Discussion The influence of marginal consumption in comparative LCAs is relevant to consider in situations with large differences in
the price of the product alternatives being compared, and in situations with minor differences in the impact potentials related
to the alternatives. However, different uncertainties are linked to determining the pattern for marginal consumption and the
environmental impact potential related to this. These are first of all related to the method used, but also include inaccurate
data of consumption in households, aggregation and weighting of income groups, aggregation of product groups, estimation and
size of the price difference, and the general applicability of the results.
Conclusion Incorporating marginal consumption in consequential LCAs is possible in practice. In the case study used, including the rebound
effects of the price difference has a significant influence on the result of the comparative LCA, as the result for the impact
categories acidification and nutrient enrichment changes in favour of the expensive product.
Recommendations and Perspectives It is recommended that the rebound effects of price differences should be included more frequently in LCAs. In order to ensure
this, further research in marginal consumption and investment patterns and IO data for different countries or regions is required.
Furthermore, this study does not consider the economic distributional consequences of buying an expensive product instead
of a cheaper product (e.g. related to how the profit is spent by those who provided the product). It should also be noted,
that more expensive products not necessarily result in less consumption, as those who provided the product also will spend
the money they have earned from the sale. Ideally, these consequences should also be further investigated. Likewise, the development
of databases to include marginal consumption in PC-tools is needed. In general, considerations of marginal consumption would
favour expensive product alternatives, depending, however, on the type of consumer.
ESS-Submission Editor: Dr. David Hunkeler (david.hunkeler@aquaplustech.ch) 相似文献
157.
158.
[10D-3H; 3-14C]- and [10L-3H; 3-14C]arachidonic acids were incubated with human polymorphonuclear leukocytes and with human platelets. Leukotriene B4 and 5(S),12(S)-dihydroxy-6trans,8cis,10trans,14-cis-eicosatetraenoic acid (5,12-DHETE) were isolated and the 3H/14C ratios determined. It could be concluded that the 10D (pro-R)-hydrogen is eliminated in the conversion of 5(S)-hydroperoxy-6trans,8cis,11cis,14cis-eicosatetraenoic acid into leukotriene A4 whereas in the conversion of arachidonic acid into 5,12-DHETE the 10L (pro-S)-hydrogen is lost. Incubation of the doubly labeled arachidonic acids with human platelets confirmed and extended previous data on the stereochemistry of the hydrogen removal from C-10 during the conversion into 12(S)-hydroperoxy-5cis,8cis,10trans,14cis-eicosatetraenoic acid, i.e., the 10L (pro-S)-hydrogen is eliminated and the 10D (pro-R)-hydrogen retained. 相似文献
159.
几种杀虫剂对南美斑潜蝇及其寄生蜂潜蝇茧蜂的毒力 总被引:1,自引:0,他引:1
测定了阿维菌素、灭蝇胺、杀虫单、毒死蜱、灭多威、顺式氯氰菊酯6种杀虫剂对南美斑潜蝇2龄幼虫、成虫及其寄生蜂潜蝇茧蜂的室内毒力,并考察了灭蝇胺、阿维菌素和杀虫单对南美斑潜蝇的田间防效。在所研究浓度下,阿维菌素、灭蝇胺对2龄幼虫的毒力较高,但对南美斑潜蝇成虫和潜蝇茧蜂的毒力较低;杀虫单对南美斑潜蝇成虫、2龄幼虫和潜蝇茧蜂的毒力均较高;毒死蜱、灭多威、顺式氯氰菊酯对南美斑潜蝇2龄幼虫的毒力较低,而对潜蝇茧蜂的毒力较高。田间条件下,灭蝇胺、阿维菌素和杀虫单都对田间南美斑潜蝇具有较高防效。 相似文献
160.
Geister TL Lorenz MW Hoffmann KH Fischer K 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2009,179(1):87-98
Phenotypic plasticity may allow an organism to adjust its phenotype to environmental needs. However, little is known about
environmental effects on offspring biochemical composition and turnover rates, including energy budgets and developmental
costs. Using the tropical butterfly Bicyclus anynana and employing a full-factorial design with two oviposition and two developmental temperatures, we explore the consequences
of temperature variation on egg and hatchling composition, and the associated use and turnover of energy and egg compounds.
At the lower temperature, larger but fewer eggs were produced. Larger egg sizes were achieved by provisioning these eggs with
larger quantities of all compounds investigated (and thus more energy), whilst relative egg composition was rather similar
to that of smaller eggs laid at the higher temperature. Turnover rates during embryonic development differed across developmental
temperatures, suggesting an emphasis on hatchling quality (i.e. protein content) at the more stressful lower temperature,
but on storage reserves (i.e. lipids) at the higher temperature. These differences may represent adaptive maternal effects.
Embryonic development was much more efficient at the lower temperature, providing a possible mechanism underlying the temperature-size
rule. 相似文献