Phytosociological and habitat studies of the phytocoenoses of Luronium natans have been conducted. The present results were compared with data on L. dortmanna and I. lacustris. It is demonstrated that the community of L. natans differs from the other two communities with respect to habitat conditions despite the fact that they have been reported to occur jointly and alongside in Lobelia lakes. It appears that significant differences between the communities are found not only regarding their waters, but also their substrates. L. natans dominated phytocoenoses are confined to oligotrophic, extremely soft waters, markedly poor in Ca2+, but richer in Na+ and SO42- than those of Lobelia and Isoëtes. Luronium natans develops best on acidic, highly hydrated substrates rich in organic matter, NO3– and total N. The results obtained indicate that L. natans and the phytocoenoses formed by it are characterized by their narrow ecological amplitude in Poland as opposed to those occurring in western Europe, which tolerate a relatively wide range of habitats. The present findings confirm the data from numerous works, which point to the weak competitive ability of the species compared with species typical of eutrophic waters. 相似文献
We have elaborated a method which has allowed us to estimate the direction of translocation of orthologs which have changed,
during the phylogeny, their positions on chromosome in respect to the leading or lagging role of DNA strands. We have shown
that the relative number of translocations which have switched positions of genes from the leading to the lagging DNA strand
is lower than the number of translocations which have transferred genes from the lagging strand to the leading strand of prokaryotic
genomes. This paradox could be explained by assuming that the stronger mutation pressure and selection after inversion preferentially
eliminate genes transferred from the leading to the lagging DNA strand.
Received: 12 December 2000 / Accepted: 20 April 2001 相似文献
Summary The metal distribution within mycorrhizal and nonmycorrhizal roots ofEpipactis atrorubens collected from zinc mine tailings and an area rich in heavy metal ores (both located in southern Poland) was investigated. The tailings, consisting of postflotation material, were characterised by high levels of toxic elements such as Zn, Pb, and Cd, while soil outside the tailings was also strongly enriched in heavy metals. Atomic absorption spectrometry and proton-induced X-ray emission analysis revealed that heavy metals were mostly accumulated within orchid roots. Elemental maps from proton-induced X-ray emission showed that plant root epidermis and fungal coils which had developed within cortical cells of roots collected from the zinc mine tailings were the main places of Zn and Pb accumulation, associated with increased concentrations of Fe, Cd, Ti, Mn, Si, Ca, and S. The mean content of Pb and Zn in the coils was 4 to 5 times higher than in the root epidermis. In mycorrhizal roots from the tailings a statistically significant decrease in Pb and Zn content towards the inside of the root was observed. The mean content of Pb in coils from roots of plants growing outside the tailings was about 1% of the concentration in root coils from the tailings. Coils selected from orchid roots originating from a site outside the tailings contained comparatively high concentrations of Zn, Cd, and Cu, which was probably due to the high content of these elements in the soil. The results presented suggest a biofiltering effect against heavy metals by orchid mycorrhizal fungi. 相似文献
Large-scale preparation of highly purified tonoplast from cucumber (Cucumis sativus L.) roots was obtained after centrifugation of microsome pellet (10,000 – 80,000 g) on discontinuous sucrose density gradient
(20, 28, 32 and 42 %). Lack of PEP carboxylase (cytosol marker) and cytochrome c oxidase (mitochondrial marker) together with
a slight activity of VO4-ATPase (plasma membrane marker) and NADH-cytochrome c reductase (ER marker) in tonoplast preparation confirmed its high purity.
Using latency of nitrate-inhibited ATPase and H+ pumping as criteria it was established that the majority of tonoplast vesicles were sealed and oriented right(cytoplasmic)-side-out.
Strong acidification of the interior of vesicles observed at the presence of both, ATP and PPi, confirmed that obtained tonoplast contains two classes of proton pumps: V-ATPase and H+PPiase.
To examine and characterise of proton-transport systems in tonoplast, the effect of various inhibitors on H+ pumping and hydrolytic activities of ATPase and PPiase were measured. ATP-dependent activities (H+ flux and ATP hydrolysis) were specifically decreased by nitrate and bafilomycin A1, whereas the PPiase activities were reduced in the presence of fluoride and Na+ ions. Both enzymes showed a similar sensitivity to DCCD and DES. The results of experiments with KCl and NaCl suggested that
the vacuolar ATPase was stimulated by Cl−, whereas the vacuolar Ppiase requires K+ ions for its activity. 相似文献
Translocations of chloroplasts induced by blue light were investigated in both leaves and protoplasts isolated from leaf mesophyll
of Nicotiana tabacum. In the leaf tissue, the responses of chloroplasts were similar to those observed in other, higher and lower plant species.
Weak and strong light induced movements of chloroplasts towards cell walls perpendicular and parallel to the light direction,
respectively. Treatment with cytochalasin D, an actin-disturbing agent, blocked the movements. This shows that actin is involved
in the motile system of chloroplast translocation in tobacco. By monitoring the response of chloroplasts to light in isolated
protoplasts, we addressed the question whether the presence of the cell wall is necessary for the translocations of chloroplasts
to occur. In control protoplasts (isolated at room temperature from unstressed leaves), no clear light intensity-dependent
changes were observed in chloroplast distribution pattern. In contrast, in protoplasts obtained from plants treated with 4
°C for 8 h the chloroplasts maintained their responsiveness to light. Atomic Force Microscopy was used to measure elastic
properties of the protoplasts. Young’s modulus, which reflects rigidity of the material, was 10 times higher for protoplasts
of the coldstressed plants as compared to those isolated from the control plants. The rigidity of protoplasts isolated from
the plants treated with low temperature was reduced four-fold by exposure to cytochalasin D. It appears that the status of
protoplast actin is a factor responsible for elasticity of protoplasts. We speculate that unknown, cold stress-induced factors,
maintain the orientational movements due to anchorage of the actin cytoskeleton in the plasma membrane despite the cell wall
removal. 相似文献
A series of high pressure liquid chroamtography analyses revealed the presence of five phenolic acids in rye caryopses (vanillic,
caffeic, p-coumaric, ferulic and sinapic), three of which (p-coumaric, ferulic and sinapic) were found in the free phenolic
fraction. Ferulic acid was predominant, both among free acids and total phenolic acids (i.e. free, liberated from soluble
esters and glycosides). The highest content of the free phenolic acids in rye caryopses was observed at the beginning of development,
when on 22 DAF it was estimated at 11.55 μg·g−1 DW. During dehydratation the total level of free phenolic acids in rye caryopses decreased in all investigated samples. Although
total phenolic acids contents in all samples of unripe rye caryopses always decreased after dehydration, in rye sample collected
in full ripeness (57 DAF), the amount of these compounds increased after the enforced dehydration. It should be added that
in ester-bound-soluble phenolic acids fraction (the largest part in the total phenolic acids fraction), irrespective of the
total amount decrease, much increase of sinapic acid content in this fraction was observed after dehydratation treatment in
all investigated samples of caryopses of various ripeness. During the development and ripening of rye caryopses, a gradual
increase in the precocious germination ability of the grain was observed. The enforced dehydration stimulated the process
of precocious germination of developing and ripening rye caryopses. A possible role of phenolics in preventing precocious
germination and acclimation to dehydration of developing and ripening rye grains is discussed. 相似文献
Several studies have shown that plasma copper concentrations are increased in various carcinomas. Zinc acts as a cellular
growth protector, including growth of neoplastic cells, and its deficiency was demonstrated to be involved in several stages
of malignant transformation. However, the usefulness of the serum zinc and copper determinations in cancer prevention, detection,
monitoring treatment, and prognosis requires further investigations. The aim of the present study was to compare the serum
copper and zinc levels in patients with cancer of the lung (PC), breast (BC), gastrointestinal tract (GIC), and gynecological
(GYNC) malignancy with progress of the disease. The results of the study have shown a significant increase in the mean total
serum Cu levels and the serum Cu/Zn ratio in all patient groups with cancer compared to a control group. Increased mean serum
concentrations and Cu/Zn ratios were found in the whole group (ALLC), and for the GIC and GYNC groups with local as well as
metastasized (Meta) disease in comparison with the control group. The mean serum concentrations of Zn were decreased only
in metastasized ALLC and GYNC groups. 相似文献
In order to assess the effects of pollution on recruitment of brown trout (Salmo trutta f. fario L.) exposure experiments with brown trout early life stages were performed in two differently contaminated small streams near Stuttgart, southwest Germany, and in a control situation in the laboratory. Pollution in the more polluted stream is mainly due to effluents of municipal sewage treatment plants and to the influx of surface waters from areas of intense agriculture activity. Additionally, the water carries high particle loads, especially after rainfall events. Water quality of the less polluted stream is occasionally influenced by agriculture activity in the vicinity. For the exposure of trout early life stages incubators were used, which allowed frequent examinations without serious disturbance of the exposed organisms and thus the development could be monitored over time. Compared to the less polluted stream and the control, in the more polluted stream high mortality rates, the lowest hatching success, and lowest values for growth occurred. In the less polluted stream, mortality rates were comparably low in prehatching stages, but high in hatchlings and juveniles due to heavy infestations with protozoic ectoparasites Chilodonella cyprini (Moroff, 1902) and Ichthyobodo necator (Henneguy, 1883). However, pollution-related effects were not detected in this stream. Differences in developmental rates between the different treatments were correlated with different water temperatures in the two streams and the control. For the more polluted stream, previous studies have indicated embryotoxic potentials mediated by pollutants. The present study indicates that in this steam, additionally, fine solids which infiltrate stream gravels may seriously affect development of brown trout early life stages. 相似文献
The restored Maltañski Reservoir was studied from its filling with water in 1990 till 2000. Total phosphorus, chlorophyll-a, and Secchi depth, as well as the Carlson's trophic state index (TSI) values based on those three parameters showed characteristic patterns of changes among seasons and years. Within each year, the lowest trophic state was usually observed in winter and the highest in summer. Because of the high loads of phosphorus received by the reservoir, this element did not limit primary production. TSI values calculated on the basis of total phosphorus were always markedly higher than calculated on chlorophyll-a and Secchi depth (similar to each other). The trophic upsurge phase lasted only a few months after the filling of the reservoir in 1990. Similar symptoms were observed after its refilling in the spring of 1993. The trophic depression phase lasted until the end of 1995. After that time a significant correlation between phosphorus concentration in the reservoir and in river waters flowing into the reservoir was observed. The successive phases of reservoir ageing, determined on the basis of phosphorus concentration, were not accompanied by changes in chlorophyll-a content. The influence of the top-down mechanism (biomanipulation effect) resulted in relatively low values of chlorophyll-a after the filling of the reservoir with water in 1990 and in 1993. As early as 1992 chlorophyll-a values reached a very high level and stayed at that level until the end of the study in 2000 (except for the short decline in 1993).
Vegetative reproduction is a very common alternative by which plants can contribute to the next generations. There are many considerations predicting which mode of reproduction, vegetative or sexual, should be favored and numerous experimental studies to verify them. However, the results are inconsistent especially when the effect of plant density is considered. I apply here a dynamic optimization model to predict the rate of vegetative and sexual reproduction in plants as a response to changes in the local plant density. The population is assumed to occupy a heterogeneous environment consisting of patches in which growth and reproduction of plants are possible and unfavorable space between them. As the environment is globally stable, the seeds, which can disperse without restriction, exhibit a constant recruitment rate. The ramets are assumed to settle only within the patch of the mother plant. The rate of ramet production effects local density, which in turn determines ramet recruitment. The optimal strategy maximizes the expected lifetime genetic contribution, realized via both vegetative and sexual reproduction. The solutions obtained under these assumptions are dualistic. The model predicts that different approaches applied in studying the effect of ramet density should give opposite outcomes. When the comparison is between patches in natural populations, a positive relationship between relative ramet allocation and density is expected. When the density is experimentally manipulated or its effect is analyzed across different successional stages, a negative relationship should be found. The results seem to be confirmed by empirical studies. 相似文献