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1.
The effects of three conditions likely to affect soluble carbohydrate pools, namely drought, expression of barley sucrose: fructan 6-fructosyl transferase (6-SFT, EC 2.4.1.10) and the establishment of the arbuscular mycorrhizal symbiosis with Glomus mosseae were studied in a multifactorial experiment using tobacco ( Nicotiana tabacum ). Tobacco, a plant naturally unable to form fructan, accumulated fructan in leaves, and to a larger extent in the roots, when transformed with 6-SFT. Under drought conditions, growth was considerably reduced, but neither expression of 6-SFT nor mycorrhiza formation had an effect on growth rate. However, in response to drought, carbon partitioning was significantly altered towards accumulation of soluble sugars. In plants exposed to drought, pools of sucrose were greater than those of unstressed plants, particularly in their roots. In the transgenic plants expressing 6-SFT, there were also increased contents of the products of 6-SFT, namely fructan, most probably because of the increased availability of the substrate, sucrose. These effects were the same in the presence or absence of mycorrhiza. Hexoses (glucose and fructose) also increased in response to drought, primarily in the leaves. This effect of drought was little affected by the expression of 6-SFT, except that it slightly enhanced drought-induced glucose accumulation in roots. However, the presence of mycorrhiza led to a considerable reduction in drought-induced accumulation of hexoses in the leaves. The content of the fungal disaccharide trehalose was greatly increased in the roots of all mycorrhizal plants upon exposure to drought, particularly in some of the transgenic plants expressing 6-SFT.  相似文献   

2.
To study the response of non-mycorrhizal and mycorrhizal maize plants to drought, the changes in the pools of non-structural carbohydrates and amino acids were analysed in leaves and roots of two maize cvs. Plants well colonized by the arbuscular mycorrhizal fungus Glomus mosseae (Nicol. & Gerd.) (60% of root length infected) and comparable non-mycorrhizal plants were subjected to moderate drought stress by reducing the water supply. This stress induced a conspicuous increase in the trehalose pool in the mycorrhizal roots, probably because it was accumulated by the fungal symbiont. Furthermore, glucose and fructose were accumulated in leaves and roots of non-mycorrhizal plants but not in the mycorrhizal ones. Starch disappeared completely from the leaves of both mycorrhizal and non-mycorrhizal plants in response to drought. Activities of soluble acid invertase and trehalase were also measured. Acid invertase activity increased during drought in the leaves of both non-mycorrhizal and mycorrhizal plants whilst in the roots it was unaffected in non-mycorrhizal plants and decreased in the mycorrhizal ones. Without drought stress, trehalase activity was considerably higher in the leaves and roots of mycorrhizal plants than in those of non-mycorrhizal plants. It increased conspicuously during drought, primarily in the leaves of non-mycorrhizal plants. A drought-induced accumulation of amino acids as well as imino acids was found in roots and leaves of both mycorrhizal and non-mycorrhizal plants; leaves of mycorrhizal plants accumulated more imino acids than those of non-mycorrhizal ones. Our results show that drought stress and the presence of a mycorrhizal fungus have a considerable effect on carbon partitioning, imino acid and amino acid accumulation in maize plants.  相似文献   

3.
The purpose of this study was to investigate the effects of arbuscular mycorrhizal (AM) symbiosis on gas exchange, chlorophyll fluorescence, pigment concentration and water status of maize plants in pot culture under high temperature stress. Zea mays L. genotype Zhengdan 958 were cultivated in soil at 26/22°C for 6 weeks, and later subjected to 25, 35 and 40°C for 1 week. The plants inoculated with the AM fungus Glomus etunicatum were compared with the non-inoculated plants. The results showed that high temperature stress decreased the biomass of the maize plants. AM symbiosis markedly enhanced the net photosynthetic rate, stomatal conductance and transpiration rate in the maize leaves. Compared with the non-mycorrhizal plants, mycorrhizal plants had lower intercellular CO2 concentration under 40°C stress. The maximal fluorescence, maximum quantum efficiency of PSII photochemistry and potential photochemical efficiency of mycorrhizal plants were significantly higher than corresponding non-mycorrhizal plants under high temperature stress. AM-inoculated plants had higher concentrations of chlorophyll a, chlorophyll b and carotenoid than non-inoculated plants. Furthermore, AM colonization increased water use efficiency, water holding capacity and relative water content. In conclusion, maize roots inoculated with AM fungus may protect the plants against high temperature stress by improving photosynthesis and water status.  相似文献   

4.
Arbuscular mycorrhizal symbiosis has previously been shown toalter the response of sorghum leaves to probable non-hydraulicsignals of soil drying. Our objectives here were to determine:(1) how changes in phosphorus nutrition affect this root-to-shootsignalling in sorghum, (2) if mycorrhizal symbiosis can affectthe signalling process independently of effects on host P nutrition,and (3) how two Glomus species compare in their influence onsignalling. Sorghum bicolor (L.) Moench ‘G1990A’ plants weregrown with root systems split between two pots. The 332 experimentaldesign included three levels of mycorrhizae (Glomus intraradicesSchenck & Smith, Glomus etunicatum Becker & Gerd., non-mycorrhizal),three levels of phosphorus fertilization and two levels of water(fully watered, half-dried). Declines in leaf elongation with soil drying were more consistentin non-mycorrhizal than mycorrhizal plants. Relative growthrate (RGR) of both mycorrhizal and non-mycorrhizal plants initiallydeclined when water was withheld from about half of the rootsystem. With further soil drying, RGR of mycorrhizal plantseventually returned to control levels, while RGR of non-mycorrhizalplants remained depressed throughout the drying episode. Bythe end of the drying episode, mycorrhizal symbiosis had eliminateddrying-induced declines in total plant leaf length. Shoot androot dry weight declines of half-dried plants were not affectedby mycorrhizae. Declines in stomatal conductance with soil dryingwere larger and more frequent in non-mycorrhizal than mycorrhizalplants. Leaf osmotic potential and relative water content remainedsimilar in control and half-dried plants during drying, suggestingthat altered leaf behaviour of half-dried plants was due tosome non-hydraulic factor. The two fungi did not differ substantiallyin their influence on leaf behaviour. The applied phosphorustreatments did not affect either growth or stomatal responseof halfdried plants to the root-to-shoot signal, but lengthdeclines were related to actual leaf phosphorus concentrations.Rate of soil drying did not appear to influence ultimate growthreductions. We conclude that mycorrhizal fungi can modify leaf growth responseto the root-to-shoot signal of soil drying, and that this mycorrhizaleffect can occur independently of mycorrhizal effects on plantsize or phosphorus nutrition. However, plant size and nutrition,which are commonly affected by mycorrhizal symbiosis, can alsomodify the signalling process. Key words: Drought, nutrition, root signal, Sorghum bicolor, vesicular-arbuscular  相似文献   

5.
6.
The influence of the arbuscular mycorrhizal fungus Glomus deserticola on the water relations, gas exchange parameters, and vegetative growth of Rosmarinus officinalis plants under water stress was studied. Plants were grown with and without the mycorrhizal fungus under glasshouse conditions and subjected to water stress by withholding irrigation water for 14 days. Along the experimental period, a significant effect of the fungus on the plant growth was observed, and under water stress, mycorrhizal plants showed an increase in aerial and root biomass compared to non-mycorrhizal plants. The decrease in the soil water potential generated a decrease in leaf water potential (psi(l)) and stem water potential (psi(x)) of mycorrhizal and non-mycorrhizal plants, with this decrease being lower in mycorrhizal water-stressed plants. Mycorrhization also had positive effects on the root hydraulic conductivity (Lp) of water stressed plants. Furthermore, mycorrhizal-stressed plants showed a more important decrease in osmotic potential at full turgor (psi(os)) than did non-mycorrhizal-stressed plants, indicating the capacity of osmotic adjustment. Mycorrhizal infection also improved photosynthetic activity (Pn) and stomatal conductance (g(s)) in plants under water stress compared to the non-mycorrhizal-stressed plants. A similar behaviour was observed in the photochemical efficiency of PSII (Fv/Fm) with this parameter being lower in non-mycorrhizal plants than in mycorrhizal plants under water stress conditions. In the same way, under water restriction, mycorrhizal plants showed higher values of chlorophyll content than did non-mycorrhizal plants. Thus, the results obtained indicated that the mycorrhizal symbiosis had a beneficial effect on the water status and growth of Rosmarinus officinalis plants under water-stress conditions.  相似文献   

7.
We studied the response of mycorrhizal and non-mycorrhizal plants to variation in soil nutrient concentration. A model for the relative growth rate (RGR) of plant biomass was constructed with soil nutrients as an explanatory variable. A literature survey was carried out to find the relative magnitudes of parameter values for mycorrhizal and non-mycorrhizal plants. Mycorrhizal plants had higher RGR at low nutrient concentrations and non-mycorrhizal plants at high nutrient concentrations. The RGR of mycorrhizal and non-mycorrhizal plants at constant versus log-normally distributed soil nutrient concentration were compared to see the effect of mycorrhizal status on responses to variation. Variation in nutrient concentration generally reduced RGR, especially in mycorrhizal plants. The RGR of a non-mycorrhizal plant may increase with variation where a growth function threshold exists, i.e. a soil nutrient concentration that must be exceeded to allow growth. Mycorrhizal plants appeared more sensitive to variation in nutrient concentration than non-mycorrhizal plants due to the higher affinity of mycorrhizal roots at low nutrient levels. However, this prediction may be reversed if mycorrhizal symbiosis considerably stabilises flow of nutrients to plant physiological processes, such that mycorrhizal plants experience less variation in soil nutrient concentration than non-mycorrhizal plants. Our results also attain broader significance by suggesting a general trade-off between competitive ability in a constant versus variable resource availability.  相似文献   

8.
Plants from the Cyperaceae family (sedges), usually considered as non-mycorrhizal, constitute almost exclusively the herbaceous stratum of the ultramafic maquis in New Caledonia. These plants are pioneers and are important for the ecological restoration of mined areas. Costularia comosa, one of the most common sedges in this environment, was grown under field conditions on ultramafic soil, fertilized or not with phosphate and/or nitrogen. Results showed that the addition of phosphate to the soil induced a clear increase in mycorrhizal colonization of C. comosa and an increase in arbuscule abundance, reflecting the establishment of a functional mycorrhizal symbiosis. Significant positive correlations were found among mycorrhizal parameters and plant or soil phosphorus concentrations. Nitrogen fertilization did not affect mycorrhizal colonization of C. comosa. The improvement in mycorrhizal colonization by phosphate fertilization did not influence significantly nickel concentrations in the roots and shoots of plants. This study demonstrated that phosphate fertilization of ultramafic soil improved mycorrhizal colonization of C. comosa, with formation of a functional symbiosis under field conditions.  相似文献   

9.
This study investigated the effects of increasing CaCO(3) concentrations (0, 5, 10, 20?mM) on arbuscular mycorrhizal (AM) symbiosis establishment as well as on chicory root growth and mineral nutrient uptake in a monoxenic system. Although CaCO(3) treatments significantly decreased root growth and altered the symbiosis-related development steps of the AM fungus Rhizophagus irregularis (germination, germination hypha elongation, root colonization rate, extraradical hyphal development, sporulation), the fungus was able to completely fulfill its life cycle. Even when root growth decreased more drastically in mycorrhizal roots than in non-mycorrhizal ones in the presence of high CaCO(3) levels, the AM symbiosis was found to be beneficial for root mineral uptake. Significant increases in P, N, Fe, Zn and Cu concentrations were recorded in the mycorrhizal roots. Whereas acid and alkaline phosphatase enzymatic activities remained constant in mycorrhizal roots, they were affected in non-mycorrhizal roots grown in the presence of CaCO(3) when compared with the control.  相似文献   

10.
Sheng M  Tang M  Zhang F  Huang Y 《Mycorrhiza》2011,21(5):423-430
A pot experiment was conducted to examine the effect of the arbuscular mycorrhizal (AM) fungus, Glomus mosseae, on plant biomass and organic solute accumulation in maize leaves. Maize plants were grown in sand and soil mixture with three NaCl levels (0, 0.5, and 1.0 g kg−1 dry substrate) for 55 days, after 15 days of establishment under non-saline conditions. At all salinity levels, mycorrhizal plants had higher biomass and higher accumulation of organic solutes in leaves, which were dominated by soluble sugars, reducing sugars, soluble protein, and organic acids in both mycorrhizal and non-mycorrhizal plants. The relative abundance of free amino acids and proline in total organic solutes was lower in mycorrhizal than in non-mycorrhizal plants, while that of reducing sugars was higher. In addition, the AM symbiosis raised the concentrations of soluble sugars, reducing sugars, soluble protein, total organic acids, oxalic acid, fumaric acid, acetic acid, malic acid, and citric acid and decreased the concentrations of total free amino acids, proline, formic acid, and succinic acid in maize leaves. In mycorrhizal plants, the dominant organic acid was oxalic acid, while in non-mycorrhizal plants, the dominant organic acid was succinic acid. All the results presented here indicate that the accumulation of organic solutes in leaves is a specific physiological response of maize plants to the AM symbiosis, which could mitigate the negative impact of soil salinity on plant productivity.  相似文献   

11.
12.
Arbuscular mycorrhizal barley-plants were more susceptible to the obligate biotrophic shoot pathogen Erysiphe graminis f. sp. hordei. In experiments under greenhouse and open-air conditions on leaves of mycorrhizal plants, the sporulation rate of the mildew fungus was more than twice that on control plants. However, mycorrhizal plants suffered less than non-mycorrhizal plants in terms of grain number, ear yield and thousand-grain weight. Disease-yield-relationship analysis showed that the symbiosis neutralised the positive correlation between disease severity and yield loss (up to 25% infected leaf area tested). After mildew infection, nitrogen in ears of non-mycorrhizal barley was higher because of an impaired starch accumulation during grain filling. In mycorrhizal plants, leaf disease did not impair either the quantity or quality of grain yield. This improved compensation in mycorrhizal plants was related to maintained photosynthetic capacity and a delay in pathogen-induced senescence. Thus filling of long-term storage pools (fructans in internodes) and consequently reallocation of these reserves during grain filling was improved. The results suggest that higher availability of energy and material during grain formation, together with longer physiological activity, were the basis of yield maintenance and, therefore, expression of mycorrhiza-induced tolerance towards the pathogen.  相似文献   

13.
Volatile organic compounds (VOCs) emitted by plant roots have important functions that can influence the rhizospheric environment. The aim of this study was to examine the effects of arbuscular mycorrhizal (AM) fungi on the profile of root VOCs. Sorghum (Sorghum bicolor) plants were grown in pots inoculated with either Glomus mosseae or Glomus intraradices, which formed mycorrhiza with the roots. Control plants were grown in pots inoculated with sterile inoculum and did not form mycorrhiza. Forty-four VOCs were determined using headspace solid-phase microextraction (HS-SPME) and gas chromatography–mass spectrometry (GC-MS). Alkanes were the most abundant type of VOCs emitted by both mycorrhizal and non-mycorrhizal plants. Both the quantity and type of volatiles were dramatically altered by the presence of AM fungi, and these changes had species specificity. Compared with non-mycorrhizal plants, mycorrhizal plants emitted more alcohols, alkenes, ethers and acids but fewer linear-alkanes. The AM fungi also influenced the morphological traits of the host roots. The total root length and specific root length of mycorrhizal plants were significantly greater than those of non-mycorrhizal plants; however, both the incidence and length of root-hair were dramatically decreased. Our findings confirm that AM fungi can alter the profile of VOCs emitted by roots as well as the root morphology of sorghum plants, indicating that AM fungi have the potential to help plants adapt to and alter soil environments.  相似文献   

14.
Grapevine N fertilization may affect and be affected by arbuscular mycorrhizal (AM) fungal colonization and change berry composition. We studied the effects of different N fertilizers on AM fungal grapevine root colonization and sporulation, and on grapevine growth, nutrition, and berry composition, by conducting a 3.5-year pot study supplying grapevine plants with either urea, calcium nitrate, ammonium sulfate, or ammonium nitrate. We measured the percentage of AM fungal root colonization, AM fungal sporulation, grapevine shoot dry weight and number of leaves, nutrient composition (macro- and micronutrients), and grapevine berry soluble solids (total sugars or °Brix) and total acidity. Urea suppressed AM fungal root colonization and sporulation. Mycorrhizal grapevine plants had higher shoot dry weight and number of leaves than non-mycorrhizal and with a higher growth response with calcium nitrate as the N source. For the macronutrients P and K, and for the micronutrient B, leaf concentration was higher in mycorrhizal plants. Non-mycorrhizal plants had higher concentration of microelements Zn, Mn, Fe, and Cu than mycorrhizal. There were no differences in soluble solids (°Brix) in grapevine berries among mycorrhizal and non-mycorrhizal plants. However, non-mycorrhizal grapevine berries had higher acid content with ammonium nitrate, although they did not have better N nutrition and vegetative growth.  相似文献   

15.
Egerton-Warburton  L. M.  Kuo  J.  Griffin  B. J.  Lamont  B. B. 《Plant and Soil》1993,(1):481-484
The distribution of Al, Ca, Mg and P in the lateral roots and leaves of mycorrhizal and non-mycorrhizal seedlings of Eucalyptus rudis grown with and without Al was analysed using energy-dispersive X-ray microanalysis on a cryo-scanning electron microscope. Al accumulated in all tissues of nonmycorrhizal plants: the endodermis was not a barrier to the translocation of Al. In mycorrhizal roots, Al was concentrated within the sheath. The presence of Al reduced the levels of Ca and Mg in both mycorrhizal and non-mycorrhizal roots and shoots in comparison with control plants. The presence of mycorrhizas increased the levels of Ca and Mg in plants grown with Al in comparison with non-inoculated plants, although there was no evidence that mycorrhizas increased the levels of P in plants grown in Al-amended soils. P levels were higher in the mycorrhizal sheath of plants grown with Al than the controls.  相似文献   

16.
A greater understanding of how climate change will affect crop photosynthetic performance has been described as a target goal to improve yield potential. Other concomitant stressors can reduce the positive effect of elevated atmospheric CO2 on wheat yield. Arbuscular mycorrhizal fungi (AMF) are symbiotic fungi predicted to be important in defining plant responses to rising atmospheric CO2, but their role in response to global climatic change is still poorly understood. This study aimed to assess if increased atmospheric CO2 interacting with drought can modify the effects of mycorrhizal symbiosis on flag leaf physiology in winter wheat. The study was performed in climate-controlled greenhouses with ambient (400 ppm, ACO2) or elevated (700 ppm, ECO2) CO2 concentrations in the air. Within each greenhouse half of the plants were inoculated with Rhizophagus intraradices. When ear emergence began, half of the plants from each mycorrhizal and CO2 treatment were subjected to terminal drought. At ACO2 AMF improved the photochemistry efficiency of PSII compared with non-mycorrhizal plants, irrespective of irrigation regime. Mycorrhizal wheat accumulated more fructan than non-mycorrhizal plants under optimal irrigation. The level of proline in the flag leaf increased only in mycorrhizal wheat after applying drought. Mycorrhizal association avoided photosynthetic acclimation under ECO2. However, nitrogen availability to flag leaves in mycorrhizal plants was lower under ECO2 than at ACO2. Results suggest that the mechanisms underlying the interactions between mycorrhizal association and atmospheric CO2 concentration can be crucial for the benefits that this symbiosis can provide to wheat plants undergoing water deficit.  相似文献   

17.
The effects of liming and inoculation with the arbuscular mycorrhizal fungus, Glomus intraradices Schenck and Smith on the uptake of phosphate (P) by maize (Zea mays L.) and soybean (Glycine max [L.] Merr.) and on depletion of inorganic phosphate fractions in rhizosphere soil (Al-P, Fe-P, and Ca-P) were studied in flat plastic containers using two acid soils, an Oxisol and an Ultisol, from Indonesia. The bulk soil pH was adjusted in both soils to 4.7, 5.6, and 6.4 by liming with different amounts of CaCO3.In both soils, liming increased shoot dry weight, total root length, and mycorrhizal colonization of roots in the two plant species. Mycorrhizal inoculation significantly increased root dry weight in some cases, but much more markedly increased shoot dry weight and P concentration in shoot and roots, and also the calculated P uptake per unit root length. In the rhizosphere soil of mycorrhizal and non-mycorrhizal plants, the depletion of Al-P, Fe-P, and Ca-P depended in some cases on the soil pH. At all pH levels, the extent of P depletion in the rhizosphere soil was greater in mycorrhizal than in non-mycorrhizal plants. Despite these quantitative differences in exploitation of soil P, mycorrhizal roots used the same inorganic P sources as non-mycorrhizal roots. These results do not suggest that mycorrhizal roots have specific properties for P solubilization. Rather, the efficient P uptake from soil solution by the roots determines the effectiveness of the use of the different soil P sources. The results indicate also that both liming and mycorrhizal colonization are important for enhancing P uptake and plant growth in tropical acid soils.  相似文献   

18.
Tsang  Amy  Maun  M.A. 《Plant Ecology》1999,144(2):159-166
A greenhouse study was conducted to determine the effects of increasing concentrations of salt (NaCl) solutions applied to the soil containing mycorrhizal and non-mycorrhizal plants of the leguminous species Strophostyles helvola (L.) Ell. The dry weight of roots and shoots and leaf chlorophyll content of S. helvola plants decreased with an increase in the concentrations of salt solutions. Although increasing salt concentrations promoted hyphal growth in mycorrhizal plants, the percent uncolonized root surface, arbuscules and vesicles decreased. An increase in the concentration of salt solutions did not decrease the number of root nodules. The data clearly showed evidence of significantly higher chlorophyll content, shoot dry weight and number of root nodules in mycorrhizal than non-mycorrhizal plants. High salt concentrations had a negative effect on the growth of S. helvola plants but the negative effects were partially mitigated by the presence of mycorrhizal fungi.  相似文献   

19.
长期施肥对砂姜黑土丛枝菌根真菌群落的影响   总被引:4,自引:0,他引:4  
在农业生态系统中,丛枝菌根真菌(AM真菌)与很多作物的根系都存在互惠互利的共生关系,与作物的生长和健康密切相关,同时,这类特殊的真菌群落也会受到施肥等农业措施的影响.本研究依托长期定位试验4个试验处理(不施肥、单施化肥、化肥配施秸秆、化肥配施粪肥),研究砂姜黑土AM真菌群落对不同施肥措施的响应及其影响因素,探索不同处理AM真菌指示种的存在.结果表明: 砂姜黑土中的主要AM真菌类群为原囊霉科、多孢囊霉科、巨孢囊霉科、近明球囊霉科、球囊霉科和类球囊霉科;其中类球囊霉属在化肥和有机物料配施中具有显著指示作用.与对照相比,长期单施化肥显著改变AM真菌群落结构并降低其多样性,配施秸秆处理进一步降低AM真菌群落多样性,而配施粪肥明显缓解因施用化肥而造成的多样性减少现象.检验发现,导致AM真菌群落变化最主要的影响因素是土壤pH和可溶性碳.总之,长期不同有机物料和化肥配施对砂姜黑土AM真菌群落结构和多样性会产生不同影响,其中化肥配施粪肥更有利于土壤AM真菌群落多样性的维持.  相似文献   

20.
The effect of cultivation of mycorrhizal and non-mycorrhizal plants and mineral fertilization on the arbuscular mycorrhizal fungal (AMF) community structure of maize (Zea mays L.) plants was studied. Soil samples were collected from two field experiments treated for 5 years with three fertilization systems (Control – no fertilization; Mineral – NPK fertilization; and Organic – Farmyard manure fertilization). Soil samples containing soil and root fragments of rapeseed (Brassica napus L., non-mycorrhizal plant) and wheat (Triticum aestivum L., mycorrhizal plant) collected from the field plots were used as native microbial inoculum sources to maize plants. Maize plants were sown in pots containing these inoculum sources for four months under glasshouse conditions. Colonization of wheat roots by AMF, AMF community structure, AMF diversity (Shannon’s index), AMF dominance (Simpson’s index) and growth of maize were investigated. Sixteen AMF species were identified from rhizosphere soil samples as different species of genera Acaulospora, Claroideoglomus, Dentiscutata, Funneliformis, Gigaspora, Quatunica, Racocetra, and Rhizoglomus. Maize plants grown in manure-fertilized soils had a distinct AMF community structure from plants either fertilized with mineral NPK-fertilizer or non-fertilized. The results also showed that inoculum from non-mycorrhizal plants combined with mineral fertilization decreased AMF diversity (Shannon’s index), AMF dominance (Simpson’s index) and growth of maize. Our findings suggest that non-mycorrhizal plants, such as B. napus, can negatively affect the presence and the effects of soil inoculation on maize growth. Also, our results highlight the importance of considering the long-term effect of rapeseed cultivation system on the reduction of population sizes of infective AMF, and its effect on succeeding annual crops.  相似文献   

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