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1.
Two important themes in ecology include the understanding of how interactions among species control ecosystem processes, and
how habitats can be connected through transfers of nutrients and energy by mobile organisms. An impressive example of both
is the large influx of nutrients and organic matter that anadromous salmon supply to inland aquatic and terrestrial ecosystems
and the role of predation by brown bears (Ursus arctos) in transferring these marine-derived nutrients (MDN) from freshwater to riparian habitats. In spite of the recognition that
salmon-bear interactions likely play an important role in controlling the flux of MDN from aquatic to riparian habitats, few
studies have linked bear predation on salmon to processes such as nitrogen (N) or carbon (C) cycling. We combine landscape-level
survey data and a replicated bear-exclosure experiment to test how bear foraging on salmon affects nitrous oxide (N2O) flux, carbon dioxide (CO2) flux, and nutrient concentrations of riparian soils. Our results show that bears feeding on salmon increased soil ammonium
(NH4
+) concentrations three-fold and N2O flux by 32-fold. Soil CO2 flux, nitrate (NO3
−), and N transformation differences were negligible in areas where bears fed on salmon. Reference areas without concentrated
bear activity showed no detectable change in soil N cycling after the arrival of salmon to streams. Exclosure experiments
showed that bear effects on soil nutrient cycles were transient, and soil N processing returned to background conditions within
1 year after bears were removed from the system. These results suggest that recipient ecosystems do not show uniform responses
to MDN inputs and highlight the importance of large mobile consumers in generating landscape heterogeneity in nutrient cycles. 相似文献
2.
We quantified the amount, spatial distribution, and importance of salmon (Oncorhynchus spp.)-derived nitrogen (N) by brown bears (Ursus arctos) on the Kenai Peninsula, Alaska. We tested and confirmed the hypothesis that the stable isotope signature (δ15N) of N in foliage of white spruce (Picea glauca) was inversely proportional to the distance from salmon-spawning streams (r=–0.99 and P<0.05 in two separate watersheds). Locations of radio-collared brown bears, relative to their distance from a stream, were
highly correlated with δ15N depletion of foliage across the same gradient (r=–0.98 and –0.96 and P<0.05 in the same two separate watersheds). Mean rates of redistribution of salmon-derived N by adult female brown bears were
37.2±2.9 kg/year per bear (range 23.1–56.3), of which 96% (35.7±2.7 kg/year per bear) was excreted in urine, 3% (1.1±0.1 kg/year
per bear) was excreted in feces, and <1% (0.3± 0.1 kg/year per bear) was retained in the body. On an area basis, salmon-N
redistribution rates were as high as 5.1±0.7 mg/m2 per year per bear within 500 m of the stream but dropped off greatly with increasing distance. We estimated that 15.5–17.8%
of the total N in spruce foliage within 500 m of the stream was derived from salmon. Of that, bears had distributed 83–84%.
Thus, brown bears can be an important vector of salmon-derived N into riparian ecosystems, but their effects are highly variable
spatially and a function of bear density.
Received: 11 February 1999 / Accepted: 7 July 1999 相似文献
3.
4.
Sublittoral hard bottom biocoenoses in Balsfjord, Norway (69°31′ N, 19°1′ E), were monitored using underwater stereophotogrammetry.
The study includes manipulation of natural densities of organisms and testing the importance of biological interactions and
“key species ” for the structure of biocoenoses. Underwater photography has the advantages of being a non-destructive method,
but it is selective because small or hidden organisms cannot always be observed. Field experiments with exclusion of organisms
from cages seem suitable for testing hypotheses concerning which animals are “key species ” in certain biocoenoses. Sea-urchins(Strongylocentrotus droebachiensis, S. pallidus) were suspected to be “key species ” in the present study, and their removal from cages caused an increase in abundance of
barnacles(Balanus balanoides), the limpetAcmaea testudinalis and algal cover. 相似文献
5.
Woody plant encroachment of savanna ecosystems has been related to altered disturbance regimes, mainly fire suppression and
herbivore exclusion. In contrast, neighbourhood interactions among resident and colonising woody species have received little
attention, despite their likely influence on the pattern and rate of tree establishment. We examined how resident palm trees
(Butia yatay) and established adults of two riparian forest tree species (Allophylus edulis and Sebastiania commersoniana) influenced seed arrival and seedling performance of the latter two species in a humid savanna of east-central Argentina.
Seed traps and seedlings of both riparian species were placed in herbaceous openings, and beneath palm, conspecific and heterospecific
adult trees in two unburned savanna patches, and were monitored for 2 years. Only seeds of the bird-dispersed Allophylus arrived in palm microsites, yet survival of Allophylus seedlings near adult palms was limited by animal damage through trampling and burrowing, a non-trophic mechanism of apparent
competition. Seeds of both riparian species dispersed into conspecific microsites, although adult trees selectively reduced
growth of conspecific seedlings, a pattern consistent with the “escape hypothesis”. Further, survival of Sebastiania increased in the moister Allophylus microsites, suggesting a one-way facilitative interaction between woody colonisers. Our results indicate that dispersal facilitation
by resident savanna trees may be critical to riparian species invasion after fire suppression. Distance-dependent effects
of conspecific and heterospecific adult trees could contribute to shape the subsequent dynamics of woody seedling establishment.
Overall, we show that indirect interactions can play a prominent role in savanna encroachment by non-resident woody species. 相似文献
6.
Effects of Salmon-Borne Nutrients on Riparian Soils and Vegetation in Southwest Alaska 总被引:1,自引:0,他引:1
Spawning Pacific salmon (Oncorhynchus spp.) contribute marine-derived nutrients to riparian ecosystems, potentially affecting characteristics of the associated
soils and vegetation. We quantified these effects by comparing soil and vegetative characteristics upstream and downstream
of natural migratory barriers on ten spawning streams in southwest Alaska. Mean δ15N values—indicative of salmon-borne nutrients—were significantly higher in the O horizon and surface mineral soils downstream
of barriers (near spawning reaches) than in soils upstream of barriers (near non-spawning reaches). However, the mean total
N concentration in surface mineral soil was lower downstream than upstream. Mean foliar δ15N values were higher downstream for three plant species (Picea glauca, Salix alaxensis and Arctagrostis latifolia) with contrasting physiognomies. Mean overstory stem density was 100% higher downstream, primarily due to a fivefold difference
in the density of large-diameter willows (Salix spp.). Mean understory stem density was 47% lower downstream, also driven by a difference in willow density. Mean ground
layer non-vascular and dwarf shrub species covers were 28% and 73% lower downstream, respectively. Of the ten soil and vegetative
characteristics that differed upstream to downstream, two (O horizon and Picea glauca δ15N) were correlated with the density of spawning salmon. Collectively, the data suggest that salmon-borne nutrients alter riparian
soils and vegetation, while factors unrelated to salmon are responsible for the ultimate expression of many community characteristics. 相似文献
7.
A. M. Prokofiev 《Journal of Ichthyology》2007,47(1):1-20
This study reviews the nominal taxa within the species “Nemachilus” stoliczkae and “N.” dorsonotatus, described by Herzenstein (1888). N. dorsonotatus, N. d. retropinnis, and N. plagiognathus are reviewed within the species Triplophysa stoliczkae; it is suggested that this species is represented by at least 5 subspecies. N. stoliczkae brevicauda, N. s. leptosoma (synonym, N. s. productus), and N. s. crassicauda are considered as valid species, the last 2 are related to the group including the species T. tenuis, T. choprai, T. tenuicauda, and T. yasinensis rather than with T. stoliczkae. It was shown that the “stoliczkae” species group (sensu Prokofiev, 2001) should be divided into three species groups: “stoliczkae” (s. str.), “tenuis,” and “robusta”; their diagnoses and the species composition are presented. A new species from the “stoliczkae” group is described (T. scapanognatha sp. nova), related to T. tanggulaensis (Zhu, 1982).
Original Russian Text ? A.M. Prokofiev, 2007, published in Voprosy Ikhtiologii, 2007, Vol. 47, No. 1, pp. 5–25. 相似文献
8.
The importance of facilitative processes due to the presence of nitrogen-fixing legumes in temperate grasslands is a contentious
issue in biodiversity experiments. Despite a multitude of studies of fertilization effects of legumes on associated nonfixers
in agricultural systems, we know little about the dynamics in more diverse systems. We hypothesised that the identity of target
plant species (phytometers) and the diversity of neighbouring plant species would affect the magnitude of such positive species
interactions. We therefore sampled aboveground tissues of phytometers planted into all plots of a grassland biodiversity–ecosystem
functioning experiment and analysed their N concentrations, δ15N values and biomasses. The four phytometer species (Festuca pratensis, Plantago lanceolata, Knautia arvensis and Trifolium pratensis) each belonged to one of the four plant functional groups used in the experiment and allowed the effects of diversity on
N dynamics in individual species to be assessed. We found significantly lower δ15N values and higher N concentrations and N contents (amount of N per plant) in phytometer species growing with legumes, indicating
a facilitative role for legumes in these grassland ecosystems. Our data suggest that the main driving force behind these facilitative
interactions in plots containing legumes was reduced competition for soil nitrate (“nitrate sparing”), with apparent N transfer
playing a secondary role. Interestingly, species richness (and to a lesser extent functional group number) significantly decreased
δ15N values, N concentrations and N content irrespective of any legume effect. Possible mechanisms behind this effect, such as
increased N mineralisation and nitrate uptake in more diverse plots, now need further investigation. The magnitude of the
positive interactions depended on the identity of the phytometer species. Evidence for increased N uptake in communities containing
legumes was found in all three nonlegume phytometer species, with a subsequent strong increase in biomass in the grass F. pratensis across all diversity levels, and a lesser biomass gain in P. lanceolata and K. arvensis. In contrast, the legume phytometer species T. pratense was negatively affected when other legumes were present in their host communities across all diversity levels. 相似文献
9.
Trophic ecology of Pacific salmon (<Emphasis Type="Italic">Oncorhynchus</Emphasis> spp.) in the ocean: a synthesis of stable isotope research 总被引:1,自引:0,他引:1
Increasing interest in the marine trophic dynamics of Pacific salmon has been motivated by the recognition of their sensitivity
to changing climate and to the competitive effects of hatchery fish on wild stocks. It has become more common to use stable
isotopes to supplement traditional diet studies of salmon in the ocean; however, there have been no integrated syntheses of
these data to determine whether stable isotope analyses support the existing conventional wisdom of feeding strategies of
the Pacific salmon. We performed a meta-analysis of stable isotope data to examine the extent of trophic partitioning among
five species of Pacific salmon during their marine lives. Pink, sockeye, and chum salmon showed very high overlap in resource
use and there was no consistent evidence for chum relying on alternative food webs dominated by gelatinous zooplankton. δ15N showed that Chinook and coho salmon fed at trophic levels higher than the other three species. In addition, these two species
were distinctly enriched in 13C, suggesting more extensive use of coastal food webs compared to the more depleted (pelagic) signatures of pink, sockeye,
and chum salmon. This paper presents the first synthesis of stable isotope work on Pacific salmon and provides δ15N and δ13C values applicable to research on the fate of the marine derived nutrients these organisms transport to freshwater and riparian
ecosystems. 相似文献
10.
Habitat-forming species increase spatial complexity and alter local environmental conditions, often facilitating a diversified assemblage of plants and animals. Removal of dominant species, therefore, can potentially lead to pronounced changes in diversity and community structure through a series of negative and positive interactions involving several components of the community. Here we test community responses to the deletion of the dominant, canopy-forming alga Hormosira banksii from the mid-intertidal zone of wave-protected rocky shores in southern New Zealand. This species was removed in winter (July) from three 3×3-m areas at each of two platforms (Kaikoura and Moeraki) on the east coast of the South Island. Initially, 59 taxa occurred in stands, but there were only four algal species with greater than 5% cover and three mobile invertebrate species with more than five individuals per 0.25 m2. By 6 months after Hormosira removal, most fucoid and coralline algae had burned off, and there were blooms of ephemeral algae in the removal plots, but almost no change within controls. After 2 years, diversity declined by 44% relative to controls at Kaikoura and 36% at Moeraki, and the amount of bare space had increased by tenfold at Kaikoura and twofold at Moeraki. Few sessile or mobile invertebrates were present. Recruitment of Hormosira occurred after 14 months in the removal plots. At this time, a “press” disturbance was initiated into one half of each removal plot to test the effects of continued removal of Hormosira on diversity. Similar “end-points” of the control and “press” removal plots were not reached after 2 years, and even after Hormosira recruitment into the original “pulse” experiment there was little recovery of the community. In this mid-intertidal system with considerable thermal stress, and perhaps in others with few perennial species, diversity and community structure can critically depend on positive associations with a single dominant species.Electronic Supplementary Material Supplementary material is available for this article at and is accessible for authorized users. 相似文献
11.
Recent ostracods (Crustacea,Ostracoda) found in lowland springs of the provinces of Piacenza and Parma (Northern Italy) 总被引:1,自引:1,他引:0
The “fontanili” are artificial aquatic ecosystems, typical of the lowland plains of Northern Italy, exploiting natural resurgences
of deep groundwater. These habitats are characterized by low variation in hydrologic, hydrochemical and thermal conditions
throughout the year. Proper management is required to prevent the spring clogging by biomass accumulation. In spite of their
importance as refugia for endangered species, many springs were completely abandoned in the last years and several of them
will disappear. We report the results of a study carried out in 2001 on 31 springs of the provinces of Piacenza and Parma,
distributed in seven areas defined on hydrological and geological considerations. Physical and chemical variables and parameters
of waters were measured and ostracod samples were collected. Most of the springs showed high nitrate concentration, due to
a diffuse pollution of agricultural origin. Twelve ostracod species in four families were identified. Ostracod valves were
analysed by scanning electron microscopy. Cypria ophtalmica was found in all the springs; other relatively common species were Cyclocypris laevis,Notodromas persica, and Prionocypris zenkeri.The maximum number of species per site was four. Cypridopsis vidua,P. zenkeri, and N. persicashowed a very localized distribution in the study area. The ostracod fauna of the “fontanili” was compared to other species
assemblages found in spring habitats and to the available information on recent freshwater ostracods reported for Italy. 相似文献
12.
Evaluating the consequences of salmon nutrients for riparian organisms: Linking condition metrics to stable isotopes 下载免费PDF全文
Carmella Vizza Beth L. Sanderson Holly J. Coe Dominic T. Chaloner 《Ecology and evolution》2017,7(5):1313-1324
Stable isotope ratios (δ13C and δ15N) have been used extensively to trace nutrients from Pacific salmon, but salmon transfer more than carbon and nitrogen to stream ecosystems, such as phosphorus, minerals, proteins, and lipids. To examine the importance of these nutrients, metrics other than isotopes need to be considered, particularly when so few studies have made direct links between these nutrients and how they affect riparian organisms. Our study specifically examined δ13C and δ15N of riparian organisms from salmon and non‐salmon streams in Idaho, USA, at different distances from the streams, and examined whether the quality of riparian plants and the body condition of invertebrates varied with access to these nutrients. Overall, quality and condition metrics did not mirror stable isotope patterns. Most notably, all riparian organisms exhibited elevated δ15N in salmon streams, but also with proximity to both stream types suggesting that both salmon and landscape factors may affect δ15N. The amount of nitrogen incorporated from Pacific salmon was low for all organisms (<20%) and did not correlate with measures of quality or condition, probably due to elevated δ15N at salmon streams reflecting historical salmon runs instead of current contributions. Salmon runs in these Idaho streams have been declining, and associated riparian ecosystems have probably seen about a 90% reduction in salmon‐derived nitrogen since the 1950s. In addition, our results support those of other studies that have cautioned that inferences from natural abundance isotope data, particularly in conjunction with mixing models for salmon‐derived nutrient percentage estimates, may be confounded by biogeochemical transformations of nitrogen, physiological processes, and even historical legacies of nitrogen sources. Critically, studies should move beyond simply describing isotopic patterns to focusing on the consequences of salmon‐derived nutrients by quantifying the condition and fitness of organisms putatively using those resources. 相似文献
13.
Jorge Wagensberg Ambrosio Garcia Ricard V. Sole 《Bulletin of mathematical biology》1990,52(6):733-740
An ecosystem can be visualized as a graph of certain preassigned trophic compartments; these nodes are then mutually connected
through the internal exchanges of material and energy. The mathematical theory of information can be applied to such a graph
in order to define two relevant indices: a measure of connectivity (the entropy H of the connections) and a measure of the
degree of the “energetic” specialization (the internal transfer of informationI). The computation of these indices in stationary real cases suggests that the observed complexity of ecosystems is conditioned
by two competing effects. The first can be interpreted as a “thermodynamical” principle related to the unavoidable irreversibility
taking place inside the system, whereas the second can be taken as a “biological” principle concerned with the selection of
some particular interactions: those which maximize the information circulating between the compartments. 相似文献
14.
An Assessment of the Impact of Chromium-Amended Sediment on a Marine Nematode Assemblage Using Microcosm Bioassays 总被引:1,自引:0,他引:1
Fehmi Boufahja Amor Hedfi Jalila Amorri Patricia Aïssa Hamouda Beyrem Ezzeddine Mahmoudi 《Biological trace element research》2011,142(2):242-255
Microcosms were used to assess the impact of chromium on free-living marine nematodes. Nematodes were exposed to three chromium
concentrations (500 ppm (dm, dry mass), 800 ppm (dm) and 1,300 ppm (dm)), and effects were examined after 4 weeks. Results
showed significant differences between univariate measures of control nematodes and those from medium- and high-chromium microcosms.
Most, decreased significantly with increasing level of chromium contamination. The medium-chromium treatment seems to be the
minimal concentration that could has a negative effect on nematodes. Results from multivariate analyses demonstrated that
responses of nematode species to chromium treatments were varied: Leptonemella aphanothecae was eliminated at all doses tested and seemed to be intolerant species to chromium; Daptonema normandicum and Sabatieria longisetosa which significantly increased at 500 ppm chromium (dm) appeared to be “opportunistic” species at this dose whereas the two
Bathylaimus species (Bathylaimus capacosus and Bathylaimus tenuicaudatus) which increased at all the doses tested seemed to be “chromium resistant”. As we think such “opportunistic” and “resistant”
species could be used as sensitive indicators of unsafe marine food. The use of microcosms has allowed the effects of the
chromium on nematodes to be assessed individually, which was not possible in the field. 相似文献
15.
Åsa Hasselquist Langefors 《Environmental Biology of Fishes》2005,74(3-4):297-308
Synopsis I combined neutral microsatellite markers with the major histocompatibility complex (MHC) class IIB to study genetic differentiation
and colonization history in Atlantic salmon, Salmo salar, in the Baltic Sea and in the north-eastern Atlantic. Baltic salmon populations have lower levels of microsatellite genetic
variation, in terms of heterozygosity and allelic richness than Atlantic populations, confirming earlier findings with other
genetic markers, suggesting that the Baltic Sea populations have been exposed to genetic bottlenecks, most likely at a founding
event. On the other hand, the level of MHC variation was similar in the Baltic and in the north-eastern Atlantic, indicating
that positive balancing selection has increased the level of MHC-variation. Both microsatellite and MHC class IIB genetic
variation give strong support to the hypothesis that the Baltic salmon are of a biphyletic origin, the southern population
in this study is strongly differentiated from both the northern Baltic salmon populations and from the north-eastern Atlantic
populations. Salmon may have colonized the northern Baltic Sea either from the south, via the so called “N?rke strait” or
from the north, via a proposed historical connection between the White Sea and the northern Baltic. At microsatellites, no
significant isolation-by distance was found at either colonization route. At the MHC, populations were significantly isolated
by distance when assuming that colonization occurred via the “N?rke strait”. 相似文献
16.
N. V. Gordeeva 《Journal of Ichthyology》2012,52(1):68-76
Variability at the locus of major histocompatibility complex MHC-I A1 in 20 populations of pink salmon Oncorhynchus gorbuscha from the five major geographical regions of the Russian Far East was studied. Indices of genetic differentiation at all levels
of the hierarchy were unexpectedly high and comparable with the corresponding estimates in related species of Pacific salmon.
The data obtained allow us to revise the existing hypotheses concerning intraspecific structure of pink salmon, in particular,
to reject the “fluctuating stock” hypothesis. Good resolution of the detected marker will find application in the problems
of identification of populations in mixed catches. 相似文献
17.
Spawning salmon deliver nutrients (salmon-derived nutrients, SDN) to natal watersheds that can be incorporated into terrestrial
and aquatic food webs, potentially increasing ecosystem productivity. Peterson Creek, a coastal watershed in southeast Alaska
that supports several species of anadromous fish, was sampled over the course of a storm during September 2006 to test the
hypothesis that stormflows re-introduce stored SDN into the stream. We used stable isotopes and PARAFAC modeling of fluorescence
excitation–emission spectroscopy to detect flushing of DOM from salmon carcasses in the riparian zone back into a spawning
stream. During the early storm hydrograph, streamwater concentrations of NH4–N and total dissolved phosphorus (TDP), the fluorescent protein tyrosine and the δ15N content of DOM peaked, followed by a rapid decrease during maximum stormflow. Although δ15N has previously been used to track SDN in riparian zones, the use of fluorescence spectroscopy provides an independent indicator
that SDN are being returned from the riparian zone to the stream after a period of intermediate storage outside the stream
channel. Our findings further demonstrate the utility of using both δ15N of streamwater DOM and fluorescence spectroscopy with PARAFAC modeling to monitor how the pool of streamwater DOM changes
in spawning salmon streams. 相似文献
18.
Varying effects of anadromous sockeye salmon on the trophic ecology of two species of resident salmonids in southwest Alaska 总被引:1,自引:0,他引:1
MARK D. SCHEUERELL JONATHAN W. MOORE DANIEL E. SCHINDLER CHRIS J. HARVEY 《Freshwater Biology》2007,52(10):1944-1956
1. Anadromous salmon transport marine‐derived nutrients and carbon to freshwater and riparian ecosystems upon their return to natal spawning systems. The ecological implications of these subsidies on the trophic ecology of resident fish remain poorly understood despite broad recognition of their potential importance. 2. We studied the within‐year changes in the ration size, composition and stable isotope signature of the diets of two resident salmonids (rainbow trout, Oncorhynchus mykiss; Arctic grayling, Thymallus arcticus) before and after the arrival of sockeye salmon (Oncorhynchus nerka) to their spawning grounds in the Bristol Bay region of southwest Alaska. 3. Ration size and energy intake increased by 480–620% for both species after salmon arrived. However, the cause of the increases differed between species such that rainbow trout switched to consuming salmon eggs, salmon flesh and blowflies that colonized salmon carcasses, whereas grayling primarily ate more benthic invertebrates that were presumably made available because of physical disturbances by spawning salmon. 4. We also observed an increase in the δ15N of rainbow trout diets post‐salmon, but not for grayling. This presumably led to the observed increase in the δ15N of rainbow trout with increasing body mass, but not for grayling. 5. Using a bioenergetics model, we predicted that salmon‐derived resources contributed a large majority of the energy necessary for growth in this resident fish community. Furthermore, the bioenergetics model also showed how seasonal changes in diet affected the stable isotope ratios of both species. These results expand upon a growing body of literature that highlights the different pathways whereby anadromous salmon influence coastal ecosystems, particularly resident fish. 相似文献
19.
The holotype of a bothid flounder,Arnoglossus tapeinosomus (Bleeker, 1866), was re-examined and found to bear none of the diagnostic characters ascribed by many authors to the species.
In addition, the shape of the prevomer was clearly different between the holotype and 18 specimens supposedly“A. tapeinosomus.” A. macrolophus Alcock, 1889, which was synonymized underA. tapeinosomus by Weber and de Beaufort (1929), is considered as a valid replacement name for“A. tapeinosomus,” because of the elongated anterior rays in the dorsal fin and a large, dark spot on the posterior dorsal and anal fin bases.A. tapeinosomus is redescribed from the holotype. 相似文献
20.
Previously, it was clarified that phycobilisome (PBS) mobility and energy spillover were both involved in light-to-dark induced
state transitions of intact Spirulina platensis cells. In this work, by taking advantage of the characteristic fluorescence spectra of photosystem I (PSI) trimers and monomers
as indicators, the relative contributions for the “mobile PBS” and “energy spillover” are quantitatively estimated by separating
the fluorescence contribution of PBS mobility from that of PSI oligomeric change. Above the phase transition temperature (T
PT) of the membrane lipids, the relative proportion of the contributions is invariable with 65% of “mobile PBS” and 35% of “energy
spillover”. Below T
PT, the proportion for the “mobile PBS” becomes larger under lowering temperature even reaching 95% with 5% “energy spillover”
at 0°C. It is known that lower temperature leads to a further light state due to a more reduced or oxidized PQ pool. Based
on the current result, it can be deduced that disequilibrium of the redox state of the PQ pool will trigger PBS movement instead
of change in the PSI oligomeric state. 相似文献