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Relatively few studies have compared invasibility and species invasiveness among microhabitats within communities, synchronously. We surveyed the abundance and performance of non-native Alternanthera philoxeroides (Mart.) Griseb. (alligator weed), its co-occurring native congener, Alternanthera sessilis (L.) DC. (sessile joyweed), and other species in a wetland community along a riparian zone in southeast China to test the hypotheses that: i) degree of invasion differs between different types of microhabitats within the community; and ii) microhabitat types that differ in invasibility also differ in soil resource availability or in sediment characteristics likely to affect resource availability; iii) phenotypic plasticity of A. philoxeroides may play a key role in its adaptation to diverse habitats as can be concluded from its extremely low genetic diversity in China. The study riparian zone comprises different types of microhabitats including wet abandoned field, swamp, marsh dunes and gravel dunes. Consistent with these hypotheses, cover of A. philoxeroides was high in abandoned fields (73 ± 2.9%) and swamps (94 ± 1.3%), which had high soil nutrients and water availability. On the contrary, cover of native A. sessilis was relatively high in marsh dunes and grave dunes, which had coarse gravel surfaces, low soil nutrients and low water availability. A. philoxeroides showed greater morphological plasticity in response to habitat variation. In abiotically harsh habitats, stems had limited growth, and were prostrate with weak adventitious roots at nodes, forming thin, scattered patches. In the two richer habitats, the highly branched plants spread over the water or soil surface, supporting dense stronger leaf-bearing stems which grew vertically. The growth pattern of A. sessilis among microhabitats did not exhibit significant variations. These results suggest that morphological plasticity and microhabitat types with high soil resources may facilitate invasions of A. philoxeroides. 相似文献
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Gene expression using an ultrathin needle enabling accurate displacement and low invasiveness 总被引:3,自引:0,他引:3
Han S Nakamura C Obataya I Nakamura N Miyake J 《Biochemical and biophysical research communications》2005,332(3):633-639
We have previously demonstrated a new cell manipulation technology by using an atomic force microscope (AFM) and ultrathin needles, named nanoneedles. The nanoneedle is an AFM tip etched by a focused ion beam (FIB) and is sharpened from 200 to 800 nm in diameter. In this study, we have evaluated the proper diameter of a needle required for insertion into human cells over a long period without causing cell death, and achieved highly efficient gene expression method for human cells using a nanoneedle and an AFM. 相似文献
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Trichostatin A,an Inhibitor of Histone Deacetylase,Inhibits the Viability and Invasiveness of Hypoxic Rheumatoid Arthritis Fibroblast‐Like Synoviocytes via PI3K/Akt Signaling 下载免费PDF全文
This study was undertaken to explore the effects of trichostatin A (TSA), an inhibitor of histone deacetylase, on the viability, apoptosis, and invasiveness of hypoxic rheumatoid arthritis fibroblast‐like synoviocytes (RA FLSs). RA FLSs were exposed to hypoxia for 24 h in the presence or absence of 2 μM TSA and tested for cell viability, apoptosis, invasion, and gene expression. The involvement of the phosphatidylinositol‐3‐kinase (PI3K)/Akt pathway was checked. TSA significantly inhibited the viability and induced apoptosis of hypoxic RA FLSs, compared to vehicle control. TSA blocked hypoxia‐induced invasion of RA FLSs during Matrigel invasion assays and reduced the expression of matrix metalloproteinases (MMP‐2 and MMP‐9) and PI3K and phosphorylation of Akt. Overexpression of constitutively active Akt reversed TSA‐mediated suppression of invasiveness and downregulation of MMP‐2 and MMP‐9. Our results indicate the antisurvival and antiinvasive activities of TSA in hypoxic RA FLSs, which is associated with inactivation of PI3K/Akt signaling. 相似文献
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Growth conditions play a major role in expression of virulence by Shigella spp. both in vitro (adherence and internalization in eukaryotic host cells) and in vivo (keratoconjunctivitis). Optimized expression of virulence required anaerobic growth to log phase in particular media such as brain heart infusion broth. Kinetic studies of guinea pig eye infections showed that as few as 2 x 10(5) S. dysenteriae CG097 or S. flexneri M90T, grown under these optimized conditions, produced keratoconjunctivitis in 15 h. In vitro studies demonstrated that adherence to and invasion of Henle 407 cells, at 37 degrees C, by organisms grown under these optimized conditions, were significantly greater than when organisms were grown aerobically under the same conditions. 相似文献
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Plant species diversity as a driver of early succession in abandoned fields: a multi-site approach 总被引:15,自引:0,他引:15
W. H. Van der Putten S. R. Mortimer K. Hedlund C. Van Dijk V. K. Brown J. Lepä C. Rodriguez-Barrueco J. Roy T. A. Diaz Len D. Gormsen G. W. Korthals S. Lavorel I. Santa Regina P. Smilauer 《Oecologia》2000,124(1):91-99
Succession is one of the most studied processes in ecology and succession theory provides strong predictability. However,
few attempts have been made to influence the course of succession thereby testing the hypothesis that passing through one
stage is essential before entering the next one. At each stage of succession ecosystem processes may be affected by the diversity
of species present, but there is little empirical evidence showing that plant species diversity may affect succession. On
ex-arable land, a major constraint of vegetation succession is the dominance of perennial early-successional (arable weed)
species. Our aim was to change the initial vegetation succession by the direct sowing of later-successional plant species.
The hypothesis was tested that a diverse plant species mixture would be more successful in weed suppression than species-poor
mixtures. In order to provide a robust test including a wide range of environmental conditions and plant species, experiments
were carried out at five sites across Europe. At each site, an identical experiment was set up, albeit that the plant species
composition of the sown mixtures differed from site to site. Results of the 2-year study showed that diverse plant species
mixtures were more effective at reducing the number of natural colonisers (mainly weeds from the seed bank) than the average
low-diversity treatment. However, the effect of the low-diversity treatment depended on the composition of the species mixture.
Thus, the effect of enhanced species diversity strongly depended on the species composition of the low-diversity treatments
used for comparison. The effects of high-diversity plant species mixtures on weed suppression differed between sites. Low-productivity
sites gave the weakest response to the diversity treatments. These differences among sites did not change the general pattern.
The present results have implications for understanding biological invasions. It has been hypothesised that alien species
are more likely to invade species-poor communities than communities with high diversity. However, our results show that the
identity of the local species matters. This may explain, at least partly, controversial results of studies on the relation
between local diversity and the probability of being invaded by aliens.
Received: 13 July 1999 / Accepted: 4 February 2000 相似文献
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Eupatorium adenophorum is one of the more noxious invasive plants worldwide. However, the mechanisms underlying its invasiveness are still not well
elucidated. In this study, we compared the invader with its two native congeners (E. heterophyllum and E. japonicum) at four irradiances in terms of growth, biomass allocation, morphology, and photosynthesis. The higher light-saturated photosynthetic
rate (P
max) and total leaf area of the invader may contribute to its higher relative growth rate (RGR) and total biomass compared with
its native congeners. Total biomass and RGR increased significantly with the increase of P
max and total leaf area. The higher support organ mass fraction and the lower root mass fraction of the invader may also contribute
to its higher RGR and biomass through increasing carbon assimilation and reducing respiratory carbon loss, respectively. The
higher growth rate of the invader increased its total leaf area, ramet number, and crown area. These traits may help the invader
to form dense monoculture, outshading native plant species. However, consistently higher leaf area ratio, specific leaf area,
and leaf mass fraction were not found across irradiances for the invader compared with its native congeners. Higher plasticity
in response to irradiance was also not found for the invader. The invader retained advantages over the natives across irradiances,
while its performance decreased with lower irradiance. The results indicate that the invader may be one of the few super invaders.
Reducing irradiance may inhibit its invasions. 相似文献