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51.
The uptake of lead by two contrasting plant species, radish and red fescue, grown in soils contaminated by mine spoil was investigated. Uptake was found to be poorly correlated either with pH or total Pb concentration in the soils. By contrast, a good correlation was obtained, particularly for red fescue, between Pb uptake and Pb concentration in the solution of equilibrated soil suspensions over a wide range of soil pH, total soil Pb and soil solution Pb concentration.Calculations suggested a similar order of magnitude in the total amounts of Pb taken up by the plants and Pb in the soil solution of the root zone, justifying the latter as a good index of Pb-availability. ei]Section editor: A C Borstlap 相似文献
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A new selectively neutral mutation occurs in a multilocus genetic background that has achieved a stable equilibrium at which there is a linkage disequilibrium. Perturbation techniques are applied to an extension of the branching process formulation of Fisher in order to address the question of extinction probabilities. We show that under appropriate conditions the probability of extinction of the new mutant is increased by the existence of linkage disequilibrium in the genetic background.Research supported in part by NIH grant GM 28016 相似文献
57.
Root Morphology and Nitrogen Uptake of Maize Simultaneously Supplied with Ammonium and Nitrate in a Split-root System 总被引:11,自引:0,他引:11
We studied the response of maize (Zea mays L. cv. Anjou 256)to a simultaneous, but separated supply of ammonium and nitrate(localized supply, LS). A split-root system was used to supplyhalf of the roots with ammonium and the other half with nitrate.A homogeneously distributed supply of both nitrogen forms (HS)was the control treatment. Seedlings were grown for 12 d fromthe two-leaf to the three-leaf stage in hydroponics at threepH levels (4, 5·5 and 7). The total N concentration was3 mol m-3. The split-root system was established by removingthe seminal root system and using only four nodal roots perplant. Total root length and root surface area were recordedautomatically with a modified Delta- T area meter. Other morphologicalroot traits (such as main axis length and diameter, number,density, and length of laterals) were recorded manually. Uptakeof ammonium and nitrate was measured by the depletion of thenutrient solution. As compared with LS, HS was superior in shootand root DM, total root length and root surface area, ammoniumand nitrate uptake and shoot nitrogen concentration, irrespectiveof pH level. This indicates that, also under field conditions,mixed ammonium and nitrate fertilization is only beneficialto plant growth if both N forms are evenly distributed in thesoil. At both HS and LS, ascending pH increased the ammonium:nitrateuptake ratio. At LS, declining pH induced a considerable shiftin the distribution of root DM, root length, and root surfacearea the nitrate-fed compartment.Copyright 1993, 1999 AcademicPress Maize, Zea may L., ammonium, nitrate, pH, root morphology, split-root 相似文献
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Marco Patacca Marcus Lindner Manuel Esteban Lucas-Borja Thomas Cordonnier Gal Fidej Barry Gardiner Ylva Hauf Gediminas Jasinevičius Sophie Labonne Edgaras Linkevičius Mats Mahnken Slobodan Milanovic Gert-Jan Nabuurs Thomas A. Nagel Laura Nikinmaa Momchil Panyatov Roman Bercak Rupert Seidl Masa Zorana Ostrogović Sever Jaroslaw Socha Dominik Thom Dijana Vuletic Sergey Zudin Mart-Jan Schelhaas 《Global Change Biology》2023,29(5):1359-1376
Over the last decades, the natural disturbance is increasingly putting pressure on European forests. Shifts in disturbance regimes may compromise forest functioning and the continuous provisioning of ecosystem services to society, including their climate change mitigation potential. Although forests are central to many European policies, we lack the long-term empirical data needed for thoroughly understanding disturbance dynamics, modeling them, and developing adaptive management strategies. Here, we present a unique database of >170,000 records of ground-based natural disturbance observations in European forests from 1950 to 2019. Reported data confirm a significant increase in forest disturbance in 34 European countries, causing on an average of 43.8 million m3 of disturbed timber volume per year over the 70-year study period. This value is likely a conservative estimate due to under-reporting, especially of small-scale disturbances. We used machine learning techniques for assessing the magnitude of unreported disturbances, which are estimated to be between 8.6 and 18.3 million m3/year. In the last 20 years, disturbances on average accounted for 16% of the mean annual harvest in Europe. Wind was the most important disturbance agent over the study period (46% of total damage), followed by fire (24%) and bark beetles (17%). Bark beetle disturbance doubled its share of the total damage in the last 20 years. Forest disturbances can profoundly impact ecosystem services (e.g., climate change mitigation), affect regional forest resource provisioning and consequently disrupt long-term management planning objectives and timber markets. We conclude that adaptation to changing disturbance regimes must be placed at the core of the European forest management and policy debate. Furthermore, a coherent and homogeneous monitoring system of natural disturbances is urgently needed in Europe, to better observe and respond to the ongoing changes in forest disturbance regimes. 相似文献
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Variable subcellular localization of glycosphingolipids 总被引:6,自引:1,他引:5
Although most glycosphingolipids (GSLs) are thought to be locatedin the outer leaflet of the plasma membrane, recent evidenceindicates that GSLs are also associated with intracellular organelles.We now report that the subcellular localization of GSLs variesdepending on the GSL structure and cell type. GSL localizationwas determined by indirect immunofluorescence microscopy offixed permeabilized cells. A single GSL exhibited variable subcellularlocalization in different cells. For example, antibody to GalCeris localized primarily to the plasma membrane of HaCaT II-3keratinocytes, but to intracellular organelies in other epithelialcells. GalCer is localized to small vesicles and tubulovesicularstructures in MDCK cells, and to the surface of phase-denselipid droplets in HepG2 hepatoma cells. Furthermore, withina single cell type, individual GSLs were found to exhibit differentpatterns of subcellular localization. In HepG2 cells, LacCerwas associated with small vesicles, which differed from thephase-dense vesicles stained by anti-GalCer, and Gb4Cer wasassociated with the intermediate filaments of the cytoskeleton.Both anti-GalCer and monoclonal antibody A2B5, which binds polysialogangliosides,localized to mitochondria. The distinct subcellular localizationpatterns of GSLs raise interesting questions about their functionsin different organelles. Together with published data on theenrichment of GSLs in specific organelles and in apical plasmamembrane, these findings indicate the existence of specificsorting mechanisms that regulate the intracellular transportand localization of GSLs. cytoskeleton glycosphingolipid intracellular organelles mitochondria subcellular localization 相似文献
60.
Rena R. Wing Lucile L. Adams-Campbell Marsha D. Marcus Carol A. Janney 《Obesity (Silver Spring, Md.)》1993,1(3):193-198
Previous studies have examined the effect of ethnicity on obesity, concerns about shape and weight, and attitudes about eating. We hypothesized that geographical location would also influence these variables, and that students growing up in the northern part of the United States and attending northern colleges would differ from students from the South. To examine this, we studied a random sample of 275 African-Americans (AA) and 224 white college students in the entering class of two northern colleges (University of Pittsburgh or University of Massachusetts) or two southern colleges (Augusta or Paine College). All subjects were weighed and completed the Revised Restraint Scale and the EAT-26. AA women were heavier than white women, with no differences due to geographical location. Despite being thinner, white women reported more dietary restraint than AA women. This difference between AA and white women was apparent in both northern and southern college students. In contrast, geographical location was the strongest determinant of bulimic attitudes; both men and women at northern colleges reported higher bulimia scores than those at southern schools. Thus ethnicity appears to be a major determinant of body weight and attitudes about shape and dieting, whereas geographical location appears to exert greater influence on bulimic attitudes. 相似文献