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1.
Rando Tuvikene Kalle Truus Marju Robal Olga Volobujeva Enn Mellikov Tõnis Pehk Andres Kollist Tiiu Kailas Merike Vaher 《Journal of applied phycology》2010,22(1):51-63
The structure and composition of galactan from Furcellaria lumbricalis (furcellaran) were investigated in connection with rheological specificities, gel structure, and extraction conditions. The
polysaccharide was characterized by 13C nuclear magnetic resonance (13C-NMR) and Fourier transform infrared spectroscopy, inductively coupled plasma-optical emission spectrometry, electrothermal
atomization atomic absorption spectrometry, and gel permeation chromatography methods. The microstructure of polymer gels
was studied using a cryofixation method in combination with freeze-drying and scanning electron microscopy (SEM) techniques.
The undersulfated furcellaran backbone consists mainly of 3,6-anhydro-d-galactose (28.5–30.1%) and galactose residues, the latter being partly sulfated in positions 4 and 6, which give rise to
some specific properties of the gel. Also, residues of 6-O-methyl-d-galactose as a minor component are found to be present. The water-extracted furcellaran with the average molecular weight
about 290 kDa is rich in nitrogen, calcium, magnesium, and potassium, while the sodium content is rather low. The low sulfur
content (5.3%) and 13C-NMR spectra refer to an undersulfated nature of this galactan. The extraction of seaweeds in low concentration alkaline
solutions (instead of water) leads to a significant increase of the minimum size of the galactan particles and the value of
gel strength (more than 12 times for Rb-containing gels). The properties of the gel are dependent on specific tentacle-like
structure units present in furcellaran gels established by a high-resolution SEM. 相似文献
2.
High frequency of polyandry in a lek mating system 总被引:1,自引:0,他引:1
Lank David B.; Smith Constance M.; Hanotte Olivier; Ohtonen Arvo; Bailey Simon; Burke Terry 《Behavioral ecology》2002,13(2):209-215
The adaptive significance of polyandry by female birds in theabsence of direct benefits remains unclear. We determined thefrequencies of polyandrous mating and multiple paternity inthe ruff, a lekking shorebird with a genetic dimorphism inmale mating behavior. More than half of female ruffs mate with,
and have clutches fertilized by, more than one male. Individualfemales mate with males of both behavioral morphs more oftenthan expected. Polyandrous mating was more likely followingcopulation interference, but interference was uncommon. Themultiple paternity rate of ruffs is the highest known for avian
lekking species and for shorebirds. The general hypothesis thatpair-bond constraints are the major selective factor favoringmultiple mating in birds does not predict our findings. Activegenetic diversification, which has been widely dismissed asa functional explanation for polyandrous mating in birds, mayapply with respect to the behavioral polymorphism in ruffs becauseof a Mendelian genetic basis for male behavioral morph determinationand aspects of malemale cooperation and female choice.However, rates of multiple paternity in other species of lekkingbirds are higher than generally realized, and the potentialbenefits of diversification in general deserve further consideration. 相似文献
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A Tullus P Kupper A Sellin L Parts J Sõber T Tullus K Lõhmus A Sõber H Tullus 《PloS one》2012,7(8):e42648
At northern latitudes a rise in atmospheric humidity and precipitation is predicted as a consequence of global climate change. We studied several growth and functional traits of hybrid aspen (Populus tremula L.×P. tremuloides Michx.) in response to elevated atmospheric humidity (on average 7% over the ambient level) in a free air experimental facility during three growing seasons (2008-2010) in Estonia, which represents northern temperate climate (boreo-nemoral zone). Data were collected from three humidified (H) and three control (C) plots, and analysed using nested linear models. Elevated air humidity significantly reduced height, stem diameter and stem volume increments and transpiration of the trees whereas these effects remained highly significant also after considering the side effects from soil-related confounders within the 2.7 ha study area. Tree leaves were smaller, lighter and had lower leaf mass per area (LMA) in H plots. The magnitude and significance of the humidity treatment effect - inhibition of above-ground growth rate - was more pronounced in larger trees. The lower growth rate in the humidified plots can be partly explained by a decrease in transpiration-driven mass flow of NO(3) (-) in soil, resulting in a significant reduction in the measured uptake of N to foliage in the H plots. The results suggest that the potential growth improvement of fast-growing trees like aspens, due to increasing temperature and atmospheric CO(2) concentration, might be smaller than expected at high latitudes if a rise in atmospheric humidity simultaneously takes place. 相似文献
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Rahul Arvo Jonas Ya Xing Wang Hua Yang Jian Jun Li Liang Xu Songhomitra Panda-Jonas Jost Bruno Jonas 《PloS one》2015,10(9)
Purpose
To measure the distance between the optic disc center and the fovea (DFD) and to assess its associations.Methods
The population-based cross-sectional Beijing Eye Study 2011 included 3468 individuals aged 50+ years. The DFD was measured on fundus photographs.Results
Readable fundus photographs were available for 2836 (81.8%) individuals. Mean DFD was 4.76 ± 0.34mm (median: 4.74 mm; range: 3.76–6.53mm). In multivariate analysis, longer DFD was associated with longer axial length (P<0.001; standardized correlation coefficient beta: 0.62), higher prevalence of axially high myopia (P<0.001; beta:0.06), shallower anterior chamber depth (P<0.001; beta:-0.18), thinner lens thickness (P = 0.004; beta: -0.06), smaller optic disc-fovea angle (P = 0.02; beta: -0.04), larger parapapillary alpha zone (P = 0.008; beta: 0.05), larger parapapillary beta/gamma zone (P<0.001; beta: 0.11), larger optic disc area (P<0.001; beta: 0.08), lower degree of cortical cataract (P = 0.002; beta: -0.08), and lower prevalence of age-related macular degeneration (P = 0.001; beta: -0.06). Bruch´s membrane opening-fovea distance (DFD minus disc radius minus parapapillary beta/gamma zone width) in non-glaucomatous eyes was not significantly (P = 0.60) related with axial length in emmetropic or axially myopic eyes (axial length ≥23.5 mm), while it increased significantly (P<0.001; r: 0.32) with longer axial length in eyes with an axial length of <23.5mm. Ratio of mean DFD to disc diameter was 2.65 ± 0.30. If the ratio of disc-fovea distance to disc diameter was considered constant and if the individual disc diameter was calculated as the individual disc-fovea distance divided by the constant factor of 2.65, the resulting calculated disc diameter differed from the directly measured disc diameter by 0.16 ±0.13 mm (median: 0.13 mm, range: 0.00–0.89 mm) or 8.9 ± 7.3% (median: 7.4%; range: 0.00–70%) of the measured disc diameter.Conclusions
DFD (mean: 4.76mm) increases with longer axial length, larger parapapillary alpha zone and parapapillary beta/gamma zone, and larger disc area. The axial elongation associated increase in DFD was due to an enlargement of parapapillary beta/gamma zone while the Bruch’s membrane opening-fovea distance did not enlarge with longer axial length. This finding may be of interest for the process of emmetropization and myopization. Due to its variability, the disc-fovea distance has only limited clinical value as a relative size unit for structures at the posterior pole. 相似文献8.
Jan?CoppensEmail author Josef?Hejzlar Michal??orf Erik?Jeppesen ?eyda?Erdo?an Ulrike?Scharfenberger Aldoushy?Mahdy Peeter?N?ges Arvo?Tuvikene Didier?L.?Baho Cristina?Trigal Eva?Papastergiadou Kostas?Stefanidis Saara?Olsen Meryem?Beklio?luEmail author 《Hydrobiologia》2016,767(1):13-25
Coarse woody debris (CWD) represents a relatively stable habitat in many lakes with forested shorelines providing a living place for a wide range of species. The spatial complexity of CWD is recognized as an important factor promoting the abundance, diversity and productivity of littoral biota, mainly by providing shelters and moderating predator–prey interactions. However, little is as yet known on the response of different species to various levels of CWD complexity and the effects of the spatial arrangement of CWD on the connectivity between littoral populations. It is also unclear how CWD decay, which modifies the surface complexity of wood and the quality of food, affects the diversity of wood-associated species and trophic interactions. Further research is also needed to recognize the contribution of littoral wood to carbon sequestration and nutrient fluxes, considering factors affecting the CWD decay rate, such as wood species and environmental conditions. CWD resources are systematically depleted by shoreline development which leads to disruptions in the functioning of lake ecosystems. Attempts at restoring CWD habitat provided ambiguous effects on littoral species and therefore better understanding of the role of CWD in lake ecosystems is crucial to the development of successful restoration projects and effective management programmes. 相似文献
9.
Sirje?VilbasteEmail author Ain?J?rvalt Kristel?Kalpus Tiina?N?ges Peeter?Pall Kai?Piirsoo Lea?Tuvikene Peeter?N?ges 《Hydrobiologia》2016,770(1):145-164
This study is the first attempt at the European scale to make an inventory of ecosystem services (ESS) of a large lake. We analysed a set of ESS indicators against the annual mean values of environmental parameters for 2006–2013. According to principal component analysis, the trophic state- and hydrology-related factors explained about 70% of the environmental variability of the lake and showed strong relationships with some ESS. Among the provisioning ESS, the annual eel catch and the total fish catch were positively related to different eutrophication indicators while the catches of pike, bream, and burbot depended rather on hydrological factors. Reed harvesting efficiency was related to the lake’s water level. The indicators of regulating, maintenance, and cultural ESS showed very high variability in different years, the latter depending on socio-economic conditions rather than environmental factors. We discovered numerous trade-offs between ESS benefitting from higher trophic state or regulated water level of the lake and the goals of good ecological status of the lake. Our analysis showed a clear need for rules prioritizing life supporting regulatory services against other ESS. 相似文献
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Kai Piirsoo Sirje Vilbaste Jaak Truu Peeter Pall Tiiu Trei Arvo Tuvikene Malle Viik 《Aquatic Ecology》2007,41(2):183-194
Information on the structure of microalgal assemblages in the epiphyton and epilithon is necessary to understand the origin
of phytoplankton in lowland rivers. To this end, we carried out concurrent investigations on phytoplankton, epiphyton and
epilithon in 18 reaches of three Estonian rivers during the midsummers of 2002 and 2003. A total of 251 taxa was recorded,
of which 192 were epiphyton species, 158 were epilithon species and 150 were phytoplankton species. Canonical correspondence
analysis (CCA), based on the 31 most abundant taxa, indicated differences in the structure of the algal assemblages between
the different biotopes (phytoplankton, epiphyton and epilithon) as well as between the studied rivers. The composition of
the phytoplankton clearly differed from that of the other biotopes, with prevailing small flagellates, a chrysophyte (Synura uvella) and cryptophytes (Rhodomonas lacustris and Cryptomonas erosa). The epiphyton was characterized by a large number of diatoms, while the epilithic community contained filamentous cyanobacteria
(Phormidium tergestinum and Planktolyngya sp.) and a green alga (Stigeoclonium tenue) in addition to diatoms. Based on redundancy analysis (RDA), phosphorous was the most relevant parameter determining the
distribution of species in the phytoplankton assemblages. Shading by trees on the river bank, dissolved oxygen concentration
and water temperature as well as river width determined the distribution of species in the epiphyton. The data set on the
epilithon did not reveal any significant relationships between species distribution and the measured environmental parameters. 相似文献