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141.
142.
Comparison of a commercial biochemical kit and an oligonucleotide probe for identification of environmental isolates of Vibrio vulnificus 总被引:3,自引:0,他引:3
A. DALSGAARD, I. DALSGAARD, L. HØI AND J.L. LARSEN. 1996. Methods for the identification and isolation of environmental isolates of Vibrio vulnificus were evaluated. Alkaline peptone water supplemented with polymyxin B and colistin-polymyxin B-cellobiose agar were employed for the isolation of suspected V. vulnificus from water, sediment and shellfish samples. When comparing the identification of putative V. vulnificus obtained with the API 20E assay and an oligonucleotide probe, 29 API 20E profiles were obtained with only four profiles (representing 20 isolates) reaching the identification threshold of V. vulnificus among a total of 66 isolates hybridizing with the probe. The results indicated that, compared with colony hybridization, the API 20E assay was not adequate for the identification of environmental isolates of V. vulnificus . 相似文献
143.
Daphnids respond to algae-associated odours 总被引:2,自引:0,他引:2
Using a Y-tube olfactometer, it was found that Daphnia galeatax hyalina moves to the arm with odour from either of two ediblealgal species (Scenedesmus acuminatus and Oscillatoria limnetica)rather than to the alternative arm with clean water. However,no differential response was observed when odours of the toxiccyanobacterium (Oscillatoria agardhu) were tested. We suggestthat odours associated with edible algae attract Daphnia whereasnon-edible algae do not elicit attraction of Daphnia. 相似文献
144.
The importance of macrophyte bed size for cladoceran composition and horizontal migration in a shallow lake 总被引:7,自引:0,他引:7
Lauridsen Torben; Pedersen Leif Junge; Jeppesen Erik; Sonergaard Martin 《Journal of plankton research》1996,18(12):2283-2294
Cladoceran composition and diel horizontal migration were studiedin 2, 10 and 25 m diameter macrophyte exclosures establishedin the littoral zone of shallow Lake Stigsholm, Denmark. Theexclosures were protected from waterfowl grazing, but open tofish. The macrophyte community cornprized Potwnogeton pectinatus,Potamogeton pusillus and Callitriche hemaphroditica. Cladoceranswere sampled randomly every third hour inside and outside themacrophyte exclosures during a 24 h period. In the 2m exclosure,the pelagic species Ceriodaphnia spp. and Bosmina spp. dominatedduring the day, mean density being as high as 3430 indiv. l1During the night, density decreased to 1020% of the daytimedensity thus indicating diel horizontal migration. In the 10and 25 m exciosures, the daytime mean density of Ceriodaphniaspp. was 865 and 202 indiv. l1, respectively, and didnot decrease at night. In contrast to the pelagic species, thedensity of macrophyte-associated species tended to be higherin the 10 and 25 m exclosure than in the 2 m exclosure. In thedaytime, Eurycercus lamellatus density in the 2, 10 and 25 rnmacrophyte exclosures was 7, 28 and 16 indiv. l1 respectively,while that of Simocephalus vetulus was 11, 171 and 92 mdiv.l1, respectively. There was no thy-night difference inthe density of macrophyte-associated species. We conclude thatcladoceran community composition varies with macrophyte bedsize, and that the edge zone between the bed and open wateris an important daytime refuge for potentially migrating pelagiccladocerans. 相似文献
145.
Kai Larsen 《Nordic Journal of Botany》1996,16(6):636-636
146.
A novel type of DNA-binding protein interacts with a conserved sequence in an early nodulin ENOD12 promoter 总被引:3,自引:0,他引:3
147.
Summary Late Arenigian biohermal reef mounds and biostromes within the shallow-marine platform facies of the upper San Juan Formation
of the Precordillera (Western Argentina) represent a new Early Ordovician reef type. The meter-sized reefs are dominated byZondarella communis n.g. n. sp. The new taxon is characterized by domical, bulbous and laminar morphotypes exhibiting growth layers and thin
horizontal and vertical as well as intermingled skeletal elements included within different sets. The fossil maybe compared
with stromatolites and stromatoporoids but an interpretation as primitive stromatoporoids is favoured. 相似文献
148.
Summary The microproblematicumPycnoporidium ? eomesozoicum
Flügel, 1972, from Upper Triassic reefs of the Alpine-Mediterranean region, Turkey Oman and Iran (originally interpreted as possible
alga) represents the type species of a new strophomenid brachiopod genus (Gosaukammerella n.g.). The genus is characterized by a very small, millimeter-sized plano-convex shell, whose ventral valve is attached to
the substratum (mainly sponges) by symmetrically arranged outgrowths developing from a pseudopunctate, lamellose foliated
shell wall and composed of densely spaced subparallel ‘tubes’ comparable with productide spines secreted by papillose extensions
of the mantle.Gosaukammerella seems to be the only reliable candidate for the existence of post-Paleozoic strophomenid (productid ?) brachiopods.
Gosaukammerella eomesozoica is restricted to possibly cryptic, shaded reef environments inhabited predominantly by sponges serving as substrates for
micromorphic brachiopods. 相似文献
149.
Riki van den Boogaard Miriam de Boer Erik J. Veneklaas Hans Lambers 《Physiologia plantarum》1996,98(3):493-504
We have investigated the water use efficiency of whole plants and selected leaves and allocation patterns of three wheat cultivars (Mexipak, Nesser and Katya) to explore how variation in these traits can contribute to the ability to grow in dry environments. The cultivars exhibited considerable differences in biomass allocation and water use efficiency. Cultivars with higher growth rates of roots and higher proportions of biomass in roots (Nesser and Katya) also had higher leaf growth rates, higher proportions of their biomass as leaves and higher leaf area ratios. These same cultivars had lower rates of transpiration per unit leaf area or unit root weight and higher biomass production per unit water use. They also had higher ratios of photosynthesis to transpiration, and lower ratios of intercellular to external CO2 partial pressure. The latter resulted from large differences in stomatal conductance associated with relatively small differences in rates of photosynthesis. There was little variation between cultivars in response to drought, and differences in allocation pattern and plant water use efficiency between cultivars as found under well-watered conditions persisted under dry conditions. At the end of the non-watered treatment, relative growth rates and transpiration rates decreased to similar values for all cultivars. High ratios of photosynthesis to transpiration, and accordingly high biomass production per unit of transpiration, is regarded as a favourable trait for dry environments, since more efficient use of water postpones the decrease in plant water status. 相似文献
150.
Genetically stable cell lines of cucumber for the large-scale production of diploid somatic embryos 总被引:2,自引:0,他引:2
Marc Kreuger Wiert van der Meer Erik Postma Rob Abbestee Natasja Raaijmakers Gerrit-Jan van Holst 《Physiologia plantarum》1996,97(2):303-310
For the initiation of embryogenic cucumber ( Cucumis sativus L.) cell lines, from excised radicles, directly in liquid medium, the culture regime, explant density and type and concentration of hormones were adjusted so that pro-embryogenic masses (PEMs) were formed within about 8 weeks. The established cucumber cell lines were maintained tor several years without loss of embryogenic and genetic stability. The ploidy level of somatic embryos from different cucumber eell lines was either diploid or tetraploid and depended on the ploidy level of Ihe cell line. Cucumber cell lines that produced only diploid embryos were obtained by selecting completely diploid explant material and growing it in the dark during the initiation phase. Mixoploid explains could lead to tetraploid or mixoploid ceil lines. Isolation and additional selection and subculturing of single PEMs resulted in either completely diploid or tetraploid cell lines, indicating that all cells of individual PEMs are either diploid or tetraploid. The ernbryogenic cucumber cell Imes, differing only in ploidy level, were indistinguishable in growth rate and embryogetiic potential and were genetically stable over several years. 相似文献