Somatic hybrids and cybrids of Senecio fuchsii Gmel. (x) jacobaea L.

Summary In situ hybridisation and restriction fragment length polymorphism (RFLP) analysis were used to determine the relative location of the translocation breakpoint and the size of the integrated chromatin segment in hexaploid wheat-Lophopyrum translocation stocks. Three 7el₂-7D recombinant stocks were Robertsonian translocations, 7DS.7el. The remaining recombinant stock (KS10-2) was 7elS.7el-7DL and contained only the distal one-half of the long arm of 7D. The recombinant stock with 7el₁ (K11695) could be designated 7DS.7DL-7el where approximately the distal one-half of 7DL was replaced. RFLP analysis indicated that on the 7DL RFLP map the breakpoints for K11695 and KS10-2 are in different locations and that the two recombinants contain an overlapping region (a common region) of the Lophopyrum chromosome 7 in which Lr19, a leaf-rust resistant gene, is located. RFLP analysis also indicated that RFLP markers which mapped to within 1.5 cm of the centromere of chromosome 7D are located in the distal half of the long arm.     

Towards a male-only release system for SIT with the Queensland fruit fly,Bactrocera tryoni,using a genetic sexing strain with a temperature-sensitive lethal mutation

Flies that are homozygous for the recessive autosomal mutation bent wingshave a limited ability to fly and are less tolerant of high temperatures than normal flies in both the egg and puparial stages. The differences between the mutant and normal flies were found sufficient to be the basis of a genetic sexing strain. Genetic sexing strains were created using translocations of the autosome bearing the wild-type allele of bent wings(chromosome 2) to the Y chromosome, and crossing male flies carrying the translocation to mutant bent wingsfemales. In the resulting strain, the females were homozygous for the bent wingsmutation and the males were phenotypically normal for wing characters. Several translocations were recovered after irradiation, but only one translocation involving chromosome 2 was both stable and expressed in a stock that was vigorous enough for long-term viability. Unfortunately, all stocks containing the translocation showed high levels of temperature-dependent lethality, including, inexplicably, both males and females. Translocation stocks showing this effect included bent wings, another second chromosome mutation, white marks, and an otherwise normal stock. This phenomenon is probably rare, as it has not been reported before. It is likely that bent wingscould be suitably used with another translocation.     

Laboratory evalution of a translocation double heterozygote for genetic control of Aedes aegypti

Summary Two pure translocation homozygote stocks, T₁/T₁ and T₃/T₃, were used to produce a double translocation heterozygote system designated T₁/T₃, employing T₁/T₁ as the male and T₃/T₃ as the female parent. The double heterozygote showed 73 % sterility when mated to wild females. Tests on mating competitiveness, recombination frequency in the differential segment, insemination rate and inheritance of sterility after release, for four generations in laboratory cages, have been carried out to evaluate the efficiency of this strain as an agent for a population control programme.     

Development of a chromosomal arm map for wheat based on RFLP markers

Summary A chromosomal arm map has been developed for common wheat (Triticum aestivum L. em. Thell.) using aneuploid stocks to locate more than 800 restriction fragments corresponding to 210 low-copy DNA clones from barley cDNA, oat cDNA, and wheat genomic libraries. The number of restriction fragments per chromosome arm correlates moderately well with relative DNA content and length of somatic chromosomes. The chromosomal arm locations of loci detected with 6 different clones support an earlier hypothesis for the occurrence of a two-step translocation (4AL to 5AL, 5AL to 7BS, and 7BS to 4AL) in the ancestral wheat genomes. In addition, 1 clone revealed the presence of a 5AL segment translocated to 4AL. Anomalies in aneuploid stocks were also observed and can be explained by intrahomoeologous recombination and polymorphisms among the stocks. We view the development of this chromosomal arm map as a complement to, rather than as a substitute for, a conventional RFLP linkage map in wheat.Paper No. 802 of the Cornell Plant Breeding Series     

The genomic relationship between Glycine max (L.) Merr. and G. soja Sieb. and Zucc. as revealed by pachytene chromosome analysis

Summary This study was conducted with the objective of determining the genomic relationship between cultivated soybean (Glycine max) and wild soybean (G. soja) of the subgenus Soja, genus Glycine. Observations on cross-ability rate, hybrid viability, meiotic chromosome pairing, and pollen fertility in F ₁ hybrids of G. max × G. soja and reciprocals elucidated that both species hybridized readily and set mature putative hybrid pods, generated vigorous F₁ plants, had a majority of sporocytes that showed 18II + 1IV chromosome association at diakinesis and metaphase I, and had a pollen fertility that ranged from 49.2% to 53.3%. A quadrivalent was often associated with the nucleolus, suggesting that one of the chromosomes involved in the interchange is a satellited chromosome. Thus, G. max and G. soja genetic stocks used in this study have been differentiated by a reciprocal translocation. Pachytene analysis of F₁ hybrids helped construct chromosome maps based on chromosome length and euchromatin and heterochromatin distribution. Chromosomes were numbered in descending order of 1–20. Pachytene chromosomes in soybean showed heterochromatin distribution on either side of the centromeres. Pachytene analysis revealed small structural differences for chromosomes 6 and 11 which were not detected at diakinesis and metaphase I. This study suggests that G. max and G. soja carry similar genomes and validates the previously assigned genome symbol GG.Research supported in part by the Illinois Agricultural Experiment Station and U.S. Department of Agriculture Competitive Research Grant (85-CRCR-1-1616)     

闽江口芦苇与短叶茳芏空间扩展对湿地土壤磷赋存形态的影响

选择闽江口鳝鱼滩的芦苇湿地、短叶茳芏湿地以及芦苇与短叶茳芏空间扩展形成的交错带湿地为对象,研究了不同湿地土壤磷赋存形态的分布特征及其主要影响因素。结果表明,不同湿地土壤中各形态磷含量整体表现为HCl-Pi > NaOH-Pi > Residual-P > NaHCO₃-Pi > NaOH-Po > Sonic-Pi > Resin-Pi > NaHCO₃-Po。其中,难分解态磷占TP的比例最高（Resin-Pi、NaHCO₃-Pi、NaHCO₃-Po）,为48.3%-51.1%;中等易分解态磷次之（NaOH-Pi、NaOH-Po、Sonic-Pi、Sonic-Po）,为37.4%-38.8%;而易分解态磷最低（HCl-P、Residual-P）,为11.5%-12.9%。交错带湿地土壤中易分解态磷、中等易分解态磷和难分解态磷含量相对于纯群落湿地均发生了明显改变,其值相比芦苇湿地分别提高了10.6%、19.2%和22.6%,相比短叶茳芏湿地分别提高了1.6%、11.5%和16.6%,原因主要与二者空间扩展过程中交错带湿地土壤的理化性质特别是粒度组成、pH以及Fe、Al含量均较纯群落湿地发生明显改变有关。芦苇与短叶茳芏的空间扩展整体改变了湿地土壤的全磷（TP）含量和储量,相对于芦苇湿地和短叶茳芏湿地,交错带湿地土壤的TP含量分别增加了20.0%和7.1%,而磷储量分别增加了12.0%和18.0%。研究发现,芦苇与短叶茳芏的空间扩展不但改变了湿地土壤中磷的赋存状况,而且亦可能改变不同磷形态之间的转化。交错带湿地土壤磷赋存状况有助于缓解芦苇与短叶茳芏空间扩展过程中对磷养分的竞争压力,从而可能在一定程度上维持交错带湿地系统的相对稳定。     

Long-Term Nitrogen Storage and Soil Nitrogen Availability in Post-Fire Lodgepole Pine Ecosystems

Long-term, landscape patterns in inorganic nitrogen (N) availability and N stocks following infrequent, stand-replacing fire are unknown but are important for interpreting the effect of disturbances on ecosystem function. Here, we present results from a replicated chronosequence study in the Greater Yellowstone Ecosystem (Wyoming, USA) directed at measuring inorganic N availability (ion-exchange resin bags) and ecosystem N pools among 77 lodgepole pine stands that varied in age and density. Inorganic N availability ranged from 0.07 to 3.20 μN bag⁻¹ d⁻¹ and nitrate (NO₃⁻) was, on average, 65% of total resin-sorbed N. Total ecosystem N stocks (live + detrital + soil) averaged 109.9 ± 3.0 g N m⁻² (range = 63.7–185.8 g N m⁻²). Live N was 14%, detrital N was 29%, and soil N was 57% of total stocks. Soil NO₃⁻, total ecosystem N, live N, and detrital N generally increased with stand age, but soil N stocks decreased. Models (AIC_c) to predict soil N availability and N stocks included soil P, soil Ca, bulk density, and pH in addition to age (adj R ² ranged from 0.18 to 0.53) and density was included only for live N stocks. Patterns of N stocks and N availability with density were strongest for young stands (<20 years) regenerating from extensive fire in 1988; for example, litterfall N stocks increased with density (adj R ² = 0.86, P < 0.001) but inorganic N availability declined (adj R ² = 0.47, P < 0.003). Across the complex Yellowstone landscape, we conclude that N stocks and N availability are best predicted by a combination of local soil characteristics in addition to factors that vary at landscape scales (stand density and age). Overall, total ecosystem N stocks were recovered quickly following stand-replacing fire, suggesting that moderate increases in fire frequency will not affect long-term landscape N storage in Greater Yellowstone. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users. Author contributions   EAHS, MGT, and MGR conceived the study; DMK performed field research; EAHS and DMK oversaw laboratory analyses and analyzed data; EAHS wrote the paper.     

Development and molecular cytogenetic analysis of wheat-Haynaldia villosa 6VS/6AL translocation lines specifying resistance to powdery mildew

Several Triticum aestivum L.-Haynaldia villosa disomic 6VS/6AL translocation lines with powdery mildew resistance were developed from the hybridization between common wheat cultivar Yangmai 5 and alien substitution line 6V(6A). Mitotic and meiotic C-banding analysis, aneuploid analysis with double ditelosomic stocks, in situ hybridization, as well as the phenotypic assessment of powdery mildew resistance, were used to characterize these lines. The same translocated chromosome, with breakpoints near the centromere, appears to be present in all the lines, despite variation among the lines in their morphology and agronomic characteristics. The resistance gene, conferred by H. villosa and designated as Pm21, is a new and promising source of powdery mildew resistance in wheat breeding.This research was supported by grants from the National High-Tech R and D Program and the National Science and Technology Commission     

Thermal sensitivity of metabolic rates and swimming performance in two latitudinally separated populations of cod, <Emphasis Type="Italic">Gadus morhua</Emphasis> L.

Atlantic cod populations live in a wide thermal range and can differ genetically and physiologically. Thermal sensitivity of metabolic capacity and swimming performance may vary along a latitudinal gradient, to facilitate performance in distinct thermal environments. To evaluate this hypothesis, we compared the thermal sensitivity of performance in two cod stocks from the Northwest Atlantic that differ in their thermal experience: Gulf of St Lawrence (GSL) and Bay of Fundy (BF). We first compared the metabolic, physiological and swimming performance after short-term thermal change to that at the acclimation temperature (7°C) for one stock (GSL), before comparing the performance of the two stocks after short-term thermal change. For cod from GSL, standard metabolism (SMR) increased with temperature, while active metabolism (AMR, measured in the critical swimming tests), EMR (metabolic rate after an exhaustive chase protocol), aerobic scope (AS) and critical swimming speeds (U _crit and U _b–c) were lower at 3°C than 7 or 11°C. In contrast, anaerobic swimming (sprint and burst-coasts in U _crit test) was lower at 11 than 7 or 3°C. Factorial AS (AMR SMR⁻¹) decreased as temperature rose. Time to exhaustion (chase protocol) was not influenced by temperature. The two stocks differed little in the thermal sensitivities of metabolism or swimming. GSL cod had a higher SMR than BF cod despite similar AMR and AS. This led factorial AS to be significantly higher for the southern stock. Despite these metabolic differences, cod from the two stocks did not differ in their U _crit speeds. BF cod were better sprinters at both temperatures. Cod from GSL had a lower aerobic cost of swimming at intermediate speeds than those from BF, particularly at low temperature. Only the activity of cytochrome C oxidase (CCO) in white muscle differed between stocks. No enzymatic correlates were found for swimming capacities, but oxygen consumption was best correlated with CCO activity in the ventricle for both stocks. Overall, the stocks differed in their cost of maintenance, cost of transport and sprint capacity, while maintaining comparable thermal sensitivities.     

Molecular markers for wheat leaf rust resistance gene Lr41

Leaf rust, caused by Puccinia triticina Eriks., is an important foliar disease of common wheat (Triticum aestivum L.) worldwide. Pyramiding several major rust-resistance genes into one adapted cultivar is one strategy for obtaining more durable resistance. Molecular markers linked to these genes are essential tools for gene pyramiding. The rust-resistance gene Lr41 from T. tauschii has been introgressed into chromosome 2D of several wheat cultivars that are currently under commercial production. To discover molecular markers closely linked to Lr41, a set of near-isogenic lines (NILs) of the hard winter wheat cultivar Century were developed through backcrossing. A population of 95 BC₃F_2:6 NILs were evaluated for leaf rust resistance at both seedling and adult plant stages and analyzed with simple sequence repeat (SSR) markers using bulked segregant analysis. Four markers closely linked to Lr41 were identified on chromosome 2DS; the closest marker, Xbarc124, was about 1 cM from Lr41. Physical mapping using Chinese Spring nullitetrasomic and ditelosomic genetic stocks confirmed that markers linked to Lr41 were on chromosome arm 2DS. Marker analysis in a diverse set of wheat germplasm indicated that primers BARC124, GWM210, and GDM35 amplified polymorphic bands between most resistant and susceptible accessions and can be used for marker-assisted selection in breeding programs.     

Estimation of seasonal changes in translocation rates in leaves of a Japanese larch stand

To estimate the net rate of translocation in leaves of a larch stand, a new approach based on the summation method was proposed and given by a compartment model. The difference between the rate of translocation into and out of leaf biomass, namely, the net translocation rate (ΔT _r /Δt), was usually expressed by the difference between the growth rate of leaf biomass and the surplus production rate provided that the rate of leaf loss due to leaffall and grazing can be considered negligible. The rate, ΔT _r /Δt in a 19-yr-old larch stand, showed characteristic changes; it was positive from early April to late May, but after that it was negative until leaffall in late October. Our results confirmed that for the growth phase of positive ΔT _r /Δt translocation of assimilate stored in non-photosynthetic organs was indispensable for the growth. To quantify this, the ratio of ΔT _r /Δt to growth rate of leaf biomass was proposed.     

Reaction centers fromRhodopseudomonas sphaeroides in reconstituted phospholipid vesicles. II. Light-induced proton translocation

Unidirectional light-dependent proton translocation was demonstrated in a suspension of reconstituted reaction center (RC) vesicles supplemented with cytochromec and 2,3-dimethoxy-5-methyl-1,4-benzoquinone (UQ₀), a lipid-and water-soluble quinone. Proton translocation was detected only at alkaline pH. The pH dependence can be accounted for by the slow redox reaction between the reduced quinone (UQ₀H₂) and oxidized cytochromec. This conclusion is based on (i) the pH dependence of partial reactions of the reconstituted proton translocation cycle, measured either optically or electrometrically and (ii) titration studies with cytochromec and UQ₀. At 250 and 25 µM UQ₀ and cytochromec, respectively, maximal proton translocation was observed at pH 9.6. This pH optimum can be extended to a more acidic pH by increasing the concentration of the soluble redox mediators in the reconstituted cyclic electron transfer chain. At the alkaline side of the pH optimum, proton translocation appears to be limited by electron transfer from the endogenous primary to the secondary quinone within the RCs. The light intensity limits the reconstituted proton pump at the optimal pH. The results are discussed in the context of a reaction scheme for the cyclic redox reactions and the associated proton translocation events.Abbreviations RC reaction center - UQ₀/UQ₀H₂ oxidized and reduced form of 2,3-dimethoxy-5-methyl-1,4-benzoquinone - D/D⁺ reduced and oxidized form of the primary electron donor of the RCs - CCCP carbonylcyanide-trichloromethoxy phenylhydrazone - UQ_A/UQ _A ^– oxidized and semiquinone form of the primary electron acceptor of the RCs - UQ_B/UQ _B ^– /UQ_BH₂ oxidized, semiquinone, and reduced form of the secondary electron acceptor of the RCs - LDAO lauryldimethylamine-N-oxide During the course of this study K.J.H. was supported by a grant from the Netherlands Organization for the Advancement of Pure Research (Z.W.O.). This research was supported by grants from the National Institutes of Health (EY-02084) and from the Office of Naval Research (ONR-NOOO 14-79-C 0798) to M. Montal.     

Tandem repeat markers for population genetic studies of the protected California tiger salamander (<Emphasis Type="Italic">Ambystoma californiense</Emphasis>)

Habitat loss is the single greatest threat to persistence of the critically threatened California tiger salamander (Ambystoma californiense). To aid management plans that designate critical habitat for this species, I developed and characterized 21 tetranucleotide microsatellite markers using two native populations in Santa Barbara and Alameda Counties. Allelic variation and average heterozygosities were lower in the endangered Santa Barbara population (allele range 1–4, mean 2.4; H _O = 0.308 H _E = 0.288) compared with the threatened Alameda population (allele range 2–10, mean 6.7; H _O = 0.712, H _E = 0.722). In-depth population studies using these markers will provide vital information for plans to assign critical habitat that optimize gene flow among breeding populations, as well as for identifying non-native hybrid genotypes that threaten native A. californiense stocks. Beyond the conservation goals for A. californiense, the close phylogenetic relationships within the tiger salamander complex also suggest a broad utility for population studies using these markers.     

A lectin from Bryonia dioica root stocks

An N-acetylgalactosamine-specific lectin has been isolated from root stocks of Bryonia dioica by affinity chromatography on fetuin-agarose. It is a dimeric protein composed of two different subunits of relative molecular masses 32,000 and 30,000, held together by intermolecular disulphide bonds. Although most abundant in root stocks, the lectin occurs in all vegetative parts of the plant but not in seeds. Bryony lectin differs from other Cucurbitaceae lectins and from all known N-acetylgalactosamine-specific lectins.Abbreviations BDA Bryonia dioica agglutinin - M_r relative molecular mass - PBS phosphate-buffered saline - SDS-PAGE sodium dodecyl sulfate-polyacrylamide gel electrophoresis     

绿竹和麻竹地上部植硅体碳封存潜力

可以在土壤中稳定存在数千年甚至上万年之久的植硅体碳(phytolith-occluded organic carbon,PhytOC)是陆地植物生态系统长期碳封存的重要机制之一。选取福建南靖地区绿竹(Dendrocalamopsis oldhami(Munro)Keng f.)和麻竹(Dendrocalamus latiflorus Munro)两种重要丛生竹为研究对象,采集其竹叶、竹枝和竹秆样品,用微波消解法提取植硅体,采用碱溶法测定植硅体中碳含量,以比较两种丛生竹的植硅体碳封存潜力和封存速率。结果表明:绿竹和麻竹林地上部不同器官中Si含量变幅分别为4.95—37.53 g/kg和2.01—34.05 g/kg,植硅体含量变幅分别为3.35—100.80 g/kg和1.57—84.06 g/kg,两者地上部不同器官中的含量大小顺序均为叶枝秆。绿竹和麻竹林地上部不同器官干物质中的植硅体碳含量变幅分别为0.51—2.85 g/kg和0.17—2.22 g/kg。绿竹和麻竹林地上部PhytOC储量变幅分别为5.1—13.9 kg/hm~2和1.2—6.3 kg/hm~2。绿竹和麻竹地上植株不同器官中的最高PhytOC储量分别为枝和叶。绿竹和麻竹地上部PhytOC总储量分别为24.3 kg/hm~2和11.1 kg/hm~2。绿竹和麻竹林地上部PhytOC封存速率分别为0.051—0.131 t-e-CO_2hm~(-2)a~(-1)和0.0099—0.0139 t-e-CO_2hm~(-2)a~(-1),以绿竹和麻竹的最高PhytOC封存速率计算,我国绿竹林和麻竹林的地上植株部每年可分别封存1965.29 t CO_2和1520.11 t CO_2。     

Molecular mapping of <Emphasis Type="Italic">Thinopyrum</Emphasis>-derived Fusarium head blight resistance in common wheat

Resistance to Fusarium head blight (FHB) caused by Fusarium graminearum Schwabe in wheat (Triticum aestivum L.) was identified in disomic chromosome substitution and translocation lines, into which chromosome 7el₂ had been introgressed from wheatgrass, Thinopyrum ponticum. In this study, two chromosome substitution lines with different origins (designated as el₁ and el₂) and with different reactions to infection by F. graminearum were crossed to develop a segregating mapping population. The objectives of this study were to determine the effectiveness of this type II resistance and map it on chromosome 7el₂. Type II resistance to FHB was characterized in the F₂, F_2:3 families, F_4:5 plants and F_5:6 recombinant inbred lines developed by single-seed descent; and the population was characterized in the F₂ and F₅ with DNA markers along the long arm of 7el. Composite interval mapping revealed a FHB resistance QTL, designated Qfhs.pur-7EL, located in the distal region of the long arm of 7el₂ and delimited with flanking markers XBE445653 and Xcfa2240. Additive effects of Qfhs.pur-7EL reduced the number of diseased spikelets per spike following inoculation of one floret in four experiments by 1.5–2.6 and explained 15.1–32.5% of the phenotypic variation in the populations. Several STS-derived and EST-derived PCR or CAPS markers were developed in this chromosomal region, and showed the specificity of 7el₂ compared to an array of wheat lines possessing other sources of FHB resistance. These markers are useful in an effort to shorten the chromosome segment of 7el₂ and to use for marker-assisted introgression of this resistance into wheat.     

Mechanisms of arsenic hyperaccumulation in<Emphasis Type="Italic"> Pteris</Emphasis> species: root As influx and translocation

Several species of fern from the Pteris genus are able to accumulate extremely high concentrations of arsenic (As) in the fronds. We have conducted short-term unidirectional As influx and translocation experiments with ⁷³As-radiolabeled arsenate, and found that the concentration-dependent influx of arsenate into roots was significantly larger in two of these As-hyperaccumulating species, Pteris vittata (L.) and Pteris cretica cv. Mayii (L.), than in Nephrolepis exaltata (L.), a non-accumulating fern. The arsenate influx could be described by Michaelis-Menten kinetics and the kinetic parameter K _m was found to be lower in the Pteris species, indicating higher affinity of the transport protein for arsenate. Quantitative analysis of kinetic parameters showed that phosphate inhibited arsenate influx in a directly competitive manner, consistent with the hypothesis that arsenate enters plant roots on a phosphate-transport protein. The significantly augmented translocation of arsenic to the shoots that was seen in these As hyperaccumulator species is proposed to be due to a combination of the increased root influx and also decreased sequestration of As in the roots, as a larger fraction of As could be extracted from roots of the Pteris species than from roots of N. exaltata. This leaves a larger pool of mobile As available for translocation to the shoot, probably predominantly as arsenite.Abbreviations As ^V Arsenate - As ^III Arsenite - K _m Michaelis-Menten constant - P _i Phosphate - V _max Maximum rate of an enzyme-catalyzed reaction     

Geographical variation in dormancy in a copepod: evidence from population crosses

Populations of the freshwater copepod Mesocyclops edax inhabiting Michigan lakes are dormant during winter, whereas populations inhabiting Florida lakes develop and reproduce continuously throughout the year. A Michigan and a Florida population were exposed to dormancy inducing conditions (low temperature and short photoperiod) in the laboratory and observed for indications of dormancy. All Michigan individuals and a small percentage of the Florida individuals entered dormancy as indicated by prolonged duration of the fourth copepodid instar and cessation of feeding. I suggest that in these population these observations represent diapause, rather than quiescence. The two populations were crossbred to examine the nature of inheritance of dormancy. The F₁ hybrids exhibited an incidence of diapause approximately intermediate between the Florida and Michigan parental stocks. The backcrosses of F₁ individuals to the Michigan and Florida stocks, respectively, exhibited a high and an intermediate incidence of diapause. Survival of the F₂ crosses was very low. The present study presents evidence of genetic differentiation between the Michigan and Florida populations of M. edax with respect to ability to diapause.     

Characterization of the mobile charges in the membrane ofValonia utricularis

Summary An attempt for the characterization of the mobile charges has been made by investigation of the voltage relaxations following a charge pulse at various temperatures between 2 and 40°C. The translocation ratek, the membrane conductivity 1/R _m and the total concentration of mobile chargesN _t within the membrane were calculated from recently developed theory (U. Zimmermann. K.-H. Büchner and R. Benz,J. Membrane Biol. 67:183–197, 1982). Data from 21 cells show that the concentration of mobile charges does not change significantly over a temperature range of 5 to 34°C, whereas both the translocation rate and the membrane conductivity reveal a strong but reversible temperature dependence. In the temperature range of 18 to 5°C,k decreases by a factor of 10 to 20, while between 18 and 34°C the increase ink is only two- or threefold with a maximum around 25°C. In principle, the same temperature dependence was observed for the membrane conductivity. Hysteresis effects occurring in the low temperature range as well as at high temperatures indicate that a protein component is involved in the mobile charge system. Furthermore, addition of cycloheximide leads to a marked decrease in both the translocation rate and the membrane conductivity, however, leaving the concentration of mobile charges almost unchanged. Therefore, it is assumed that the mobile charges are coupled to, but not part of a carrier protein.     

Genetic changes in Atlantic salmon stocks since historical times and the effective population size of a long-term captive breeding programme

Human-caused genetic changes in two Atlanticsalmon (Salmo salar L.) stocks, from therivers Iijoki and Oulujoki in Finland, wereassessed by comparing the genetic parameters ofthese stocks before and after the hatcherybreeding of several successive generations,corresponding to 40 and 33 years since the wildstate. The changes were also compared withthose observed in a large wild salmon stock inthe River Teno during 56 years. In all, thevariation at seven microsatellite DNA loci wasexamined in 11 Atlantic salmon samplesoriginating from these three rivers. Theeffective population size, N_e, duringbreeding of the Iijoki broodstock and for theTeno salmon was also estimated by the temporalmethod based on allele frequency changes. Forthe Iijoki broodstock, the changes could betracked generation by generation from thefounding of the stock. Statisticallysignificant changes in allele frequencies werecommon in the hatchery stocks (F = 0.029, forIijoki), but not in the wild Teno stock, whichwas temporally very stable (F = 0.007). Allelicrichness decreased statistically significantly(24.8%) in the Oulujoki broodstock, from 62.1to 46.7 alleles at nine loci. On average, therewere 9.7 fewer alleles (15.7%) in thecontemporary broodstocks than in thecorresponding historical stocks. The meanheterozygosity was 6.6% lower in thecontemporary Oulujoki broodstock, but remainedunchanged in the Iijoki broodstock. Theestimated N_e for the Iijoki broodstock wasunder 80 for 4.5 generations from 1962 to 1995and for the wild Teno salmon over 900 for 56years from 1939 to 1995.