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911.
Susan J. Mazer Charles T. Schick 《Evolution; international journal of organic evolution》1991,45(8):1888-1907
To determine the effect of growing conditions on population parameters in wild radish, (Raphanus sativus L.: Brassicaceae), we replicated maternal and paternal half-sib families of seed across three planting densities in an experimental garden. A nested breeding design performed in the greenhouse produced 1,800 F1 seeds sown in the garden. We recorded survivorship, measured phenotypic correlations among and estimated narrow-sense and broad-sense heritabilities (h2) of: days to germination, days to flowering, petal area, ovule number/flower, pollen production/flower, and modal pollen grain volume. Survivorship declined with increasing density, but the relative abundances of surviving families did not differ significantly among densities. Seeds in high-density plots germinated significantly faster than seeds sown in medium- or low-density plots, but they flowered significantly later. Plants in high-density plots had fewer ovules per flower than those in the other treatments. Petal area and pollen characters did not differ significantly among densities. Densities differed with respect to the number and sign of significant phenotypic correlations. Analyses of variance were conducted to detect additive genetic variance (Va) of each trait in each density. At low density, there were significant paternal effects on flowering time and modal pollen grain volume; in medium-density plots, germination time, flowering time and ovule number exhibited significant paternal effects; in high-density plots, only pollen grain volume differed among paternal sibships. The ability to detect maternal effects on progeny phenotype also depended on density. Narrow-sense h2 estimates differed markedly among density treatments for germination time, flowering time, ovule number and pollen grain volume. Maternal, paternal and error variance components were estimated for each trait and density to examine the sources of variation in narrow-sense h2 across densities. Variance components did not change consistently across densities; each trait behaved differently. To provide qualitative estimates of genetic correlations between characters, correlation coefficients were estimated using paternal family means; these correlations also differed among densities. These results demonstrate that: a) planting density influences the magnitude of maternal and paternal effects on progeny phenotype, and of h2 estimates, b) traits differ with respect to the density in which heritability is greatest, c) density affects the variance components that comprise heritability, but each trait behaves differently, and d) the response to selection on any target trait should result in different correlated responses of other traits, depending on density. 相似文献
912.
Sérgio S. Funari 《European biophysics journal : EBJ》1998,27(6):590-594
The possibility of modifying the curvature of lipid bilayers by mixing them with additives is demonstrated and the evolution
of geometrical parameters with composition is discussed. X-ray diffraction patterns of the POPC/C12EO2/2H2O system were observed as a function of the relative humidity. The formation of an unexpected hexagonal phase indicates peculiar
behaviour in these mixtures. The cylinder radius of this phase is considerably smaller than previously observed in cubic phases.
A discussion of the head group interactions is presented. We have also been able to show that the uptake of water by the L
β
gel phase is higher as a single phase than in the L
β
+HII two phase region. The water content is important for the stabilization of HII phase and determination of its characteristic dimensions. However, it is argued that the interaction between the surfactant
and the lipid is the key factor for its formation and that the EO2 head groups displace water from the inner parts of the polar region of the mesogenic units.
Received: 22 September 1997 / Revised version: 31 December 1997 / Accepted: 10 February 1998 相似文献
913.
Non-living, freeze-dried material of the brown algaEctocarpus siliculosus (Phaeophyceae) demonstrated high equilibrium uptake of Cd from aqueous solutions (Fehrmann & Pohl, 1993). The alga was grown in 250-L photobioreactors under various growth conditions (light, salinity and nutrient concentrations) in order to obtain larger quantities of biomass and to improve its Cd adsorption capacity. To derive further knowledge on the biosorbant phenomenon different adsorption parameters such as pH for the sorption process and kinetics of Cd adsorption were tested. The maximum adsorption capacity of the freeze-dried biomass exceeded 41 mg Cd per g biomass. After repeated addition of low Cd concentrations the maximum adsorption capacity was lower (31.4 mg Cd per g biomass). In comparison with other adsorbing materials (activated carbon, silica gel, siliceous earth)E. siliculosus showed significantly higher adsorption capacity. Desorption of deposited Cd with 0.1 M HCl resulted in no changes of the adsorption capacity through five subsequent adsorption-/desorption-cycles. Hence, driedE. siliculosus appears to be an efficient material for the elimination of Cd from industrial waste water.Transmission electron microscopic investigations showed an electron dense area in the outer surface layers of the cell wall after Cd adsorption indicating the most likely location of Cd fixation.Author for correspondence 相似文献
914.
Toward a theory of dominance hierarchies: effects of assessment, group size, and variation in fighting ability 总被引:5,自引:2,他引:3
We introduce assessment to the analysis of dominance hierarchiesby exploring the effect of an evolutionarily stable fightingrule when there is variation in resource holding potential (RHP)and RHP is not a perfectly reliable predictor of the outcomeof a fight. With assessment, the probability of a linear hierarchydecreases with group size but can remain appreciable for groupsof up to seven or eight individuals, whereas it decreases virtuallyto zero if there is no assessment. The probability of a hierarchythat correlates perfectly with RHP is low unless group sizeis small. 相似文献
915.
Growth and maintenance parameters μmax, Ks, m, and Ym for cellulase biosynthesis on lactose by T. reesei-C5 were estimated and compared with published data on other soluble substrates and mutant strains of T. reesei in continuous culture. Growth was favored at higher feed lactose but cellulase productivities did not increase proportionally, suggesting that a degree of inhibition and/or catabolic repression within the strain is possible. The estimated values of growth kinetics and maintenance parameters varied little but were within a reasonable range of published data on other soluble substrates and mutant strains of T. reesei in continuous cultures. 相似文献
916.
917.
Romain Lasseur Christiane Longin‐Sauvageon Bernadette Videmann Mikaëline Billeret Philippe Berny Etienne Benoit 《Journal of biochemical and molecular toxicology》2006,19(6):379-385
A warfarin‐resistant strain and a warfarin‐susceptible strain of wild rats (Rattus norvegicus) maintained in enclosures of the National Veterinary School of Lyon (France) were studied to determine the mechanism of the resistance to anticoagulant rodenticides. A low vitamin K epoxide reductase (VKOR) activity has been reported for many resistant rat strains. As recently suggested, mutations in the vitamin K epoxide reductase subunit 1 (VKORC1) gene are the genetic basis of anticoagulant resistance in wild populations of rats from various locations in Europe. Here we report, for our strain, one of the seven described mutations (Tyr139Phe) for VKORC1 in rats. In addition, a low expression of mRNA encoding VKORC1 gene is observed in resistant rats, which could explain their low VKOR activity. We calculated kinetic parameters of VKOR in the warfarin‐resistant and warfarin‐susceptible rats. The Vmax and the Km of the VKOR obtained in resistant rats were lowered by 57 and 77%, respectively, compared to those obtained in susceptible rats. As a consequence, the enzymatic efficiency (Vm/Km) of the VKOR was similar between resistant and susceptible rats. This result could be a good explanation to the observation that no clinical signs of vitamin K deficiency was observed in the warfarin‐resistant strain, while a low VKOR activity was found. VKOR activity in warfarin‐resistant rats was poorly inhibited by warfarin (Ki for warfarin is 29 μM and 0.72 μM for resistant and susceptible rats, respectively). © 2005 Wiley Periodicals, Inc. J Biochem Mol Toxicol 19:379‐385, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/jbt.20104 相似文献
918.
Vegetative growth and photosynthesis in coffee plants under different watering and fertilization managements in Yunnan,SW China 总被引:5,自引:0,他引:5
In a field experiment Coffea arabica L. was subjected to various moisture and fertilizer regimes in Simao, Yunan, SW China. The experimental treatments consisted
of eight factorial combinations of two fertilization levels (high and low) and four watering treatments applied in the dry
season: application of dry rice straw mulch, drip irrigation, mulching plus drip irrigation on the soil surface, and control
(no mulching or irrigation). The growth of the coffee plants was monitored throughout the course of a full year. Two clear
growth peaks were detected (one at the beginning and one in the middle of the wet season) in plants subjected to all treatments,
and the growth rhythm of coffee plants was not regulated by extrinsic abiotic factors. High fertilization resulted in a significantly
higher relative growth rates for both height and length of the branches during the growth peaks than the low fertilization
treatment. In the dry season, increasing the soil moisture contents by irrigation and/or mulching enhanced the plants’ gas
exchange, but the soil water status had no significant effects on the internal fluorescence parameters of photosystem 2. More
fertilized plants had a greater ability to acclimate to high-irradiance environments than the lightly fertilized plants, showing
significant lower diurnal photoinhibition, associated with higher energy utilization through photochemistry and energy dissipation
through the xanthophyll cycle. Hence the wet season is the optimum period for photosynthetic carbon fixation and vegetative
growth of coffee plants. Higher than routinely applied levels of fertilization are required to optimize the coffee plants’
photosynthetic acclimation and growth in the studied environment. Both soil moisture conserving practices tested, mulching
and drip irrigation, had significant effects on the growth and photosynthesis of the coffee plants, but the former was more
practical than the latter. 相似文献
919.
【目的】为了进一步明确光照时间对双尾新小绥螨Neoseiulus bicaudus Wainstein生长发育的影响。【方法】在实验室恒温条件下,采用生命表研究方法,研究在不同光照时间下,双尾新小绥螨捕食土耳其斯坦叶螨的生长发育情况。【结果】双尾新小绥螨在不同光照时间段下均能完成世代周期。在光照时数小于12 h时,从卵发育至成螨的各个发育阶段所需时间均呈缩短趋势,当光照时数大于16 h后各个发育阶段所需的时间又呈增长趋势。产卵期在12L︰12D光照时数下最长为20.74 d,且同其他光照条件均存在显著性差异(P<0.05)。产卵后期、寿命、总产卵量均表现在16L︰8D光照时数下最长,分别为11.93 d、31.05 d和42.4粒。双尾新小绥螨种群的净增值率(R_0)在16L︰8D时达到最大值33.88,在8L︰16D时最低为14.97。【结论】光照时间在12~16 h范围内最适合双尾新小绥螨生长发育。 相似文献
920.
Identifyability measures to select the parameters to be estimated in a solid‐state fermentation distributed parameter model
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Christian L. da Silveira Marcio A. Mazutti Nina P. G. Salau 《Biotechnology progress》2016,32(4):905-917
Process modeling can lead to of advantages such as helping in process control, reducing process costs and product quality improvement. This work proposes a solid‐state fermentation distributed parameter model composed by seven differential equations with seventeen parameters to represent the process. Also, parameters estimation with a parameters identifyability analysis (PIA) is performed to build an accurate model with optimum parameters. Statistical tests were made to verify the model accuracy with the estimated parameters considering different assumptions. The results have shown that the model assuming substrate inhibition better represents the process. It was also shown that eight from the seventeen original model parameters were nonidentifiable and better results were obtained with the removal of these parameters from the estimation procedure. Therefore, PIA can be useful to estimation procedure, since it may reduce the number of parameters that can be evaluated. Further, PIA improved the model results, showing to be an important procedure to be taken. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 32:905–917, 2016 相似文献