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1.
Summary Transport of N by hyphae of a vesicular-arbuscular mycorrhizal fungus was studied under controlled experimental conditions. The N source was applied to the soil as 15NH inf4 sup+ or 15NO inf3 sup- . Cucumis sativus was grown for 25 days, either alone or in symbiosis with Glomus intraradices, in containers with a hyphal compartment separated from the root compartment by a fine nylon mesh. Mineral N was then applied to the hyphal compartment as 15NH inf4 sup+ or 15NO inf3 sup- at 5 cm distance from the root compartment. Soil samples were taken from the hyphal compartment at 1, 3 and 5 cm distance from the root compartment at 7 and 12 days after labelling, and the concentration of mineral N in the samples was measured from 2 M KCl extracts. Mycorrhizal colonization did not affect plant dry weight. The recovery of 15N in mycorrhizal plants was 38 or 40%, respectively, when 15NH inf4 sup+ or 15NO inf3 sup- was applied. The corresponding values for non-mycorrhizal plants were 7 and 16%. The higher 15N recovery observed in mycorrhizal plants than in non-mycorrhizal plants suggests that hyphal transport of N from the applied 15N sources towards the host plant had occurred. The concentration of mineral N in the soil of hyphal compartments was considerably less in mycorrhizal treatments than in controls, indicating that the hyphae were able to deplete the soil for mineral N.  相似文献   

2.
The influence of mineral fertilization on root uptake and arbuscular mycorrhizal fungi-mediated 15N capture from labeled legume (Medicago polymorpha) residue was examined in winegrapes (Vitis vinifera) in the greenhouse, to evaluate compatibility of fertilization with incorporation of cover-crop residue in winegrape production. Plants grown in marginal vineyard soil were either fertilized with 0.25× Hoagland’s solution or not. This low fertilization rate represents the deficit management approach typical of winegrape production. Access to residue in a separate compartment was controlled to allow mycorrhizal roots (roots + hyphae), hyphae (hyphae-intact), or neither (hyphae-rotated) to proliferate in the residue by means of mesh core treatments. Leaves were weekly analyzed for 15N. On day 42, plants were analyzed for 15N and biomass; roots were examined for intraradical colonization; and soils were analyzed for 15N, inorganic N, Olsen-P, X-K, and extraradical colonization. As expected, extraradical colonization of soil outside the cores was unaffected by mesh core treatment, while that inside the cores varied significantly. 15N atom% excess was highest in leaves of roots + hyphae. In comparison, leaf 15N atom% excess in hyphae-intact was consistently intermediate between roots + hyphae and hyphae-rotated, the latter of which remained unchanged over time. Fertilization stimulated host and fungal growth, based on higher biomass and intraradical colonization of fertilized plants. Fertilization did not affect hyphal or root proliferation in residue but did lower %N derived from residue in leaves and stems by 50%. Our results suggest that even low fertilization rates decrease grapevine N uptake from legume crop residue by both extraradical hyphae and roots.  相似文献   

3.
Summary The effects of P, N and Ca+Mg fertilization on biomass production, leaf area, root length, vesiculararbuscular mycorrhizal (VAM) colonization, and shoot and root nutrient concentrations of pretransplant rice (Oryza sativa L.) plants were investigated. Mycorrhizal plants generally had a higher biomass and P, N, K, Ca, Mn, Fe, Cu, Na, B, Zn, Al, Mg, and S shoot-tissue nutrient concentrations than non-mycorrhizal plants. Although mycorrhizal plants always had higher root-tissue nutrient concentrations than non-mycorrhizal plants, they were not significantly different, except for Mn. N fertilization stimulated colonization of the root system (colonized root length), and increased biomass production and nutrient concentrations of mycorrhizal plants. Biomass increases due to N were larger when the plants were not fertilized with additional P. P fertilization reduced the colonized root length and biomass production of mycorrhizal plants. The base treatment (Ca+Mg) did not significantly affect biomass production but increased the colonized root length. These results stress the importance of evaluating the VAM rice symbiosis under various fertilization regimes. The results of this study suggest that pretransplant mycorrhizal rice plants may have a potential for better field establishment than non-mycorrhizal plants.  相似文献   

4.
Legumes may respond to non-rhizobial inoculants such as arbuscular mycorrhizal (AM) fungi either through an effect on plant growth or, in addition, through an effect on the function of the legume-Rhizobium symbiosis. We have examined the literature where the application of 15N isotope dilution methodology permits the effect of indigenous AM and AM inoculants to be quantitatively separated into plant-growth-mediated and biological N2 fixation (BNF)-mediated components. These studies clearly demonstrate the beneficial effects that both indigenous and inoculated AM have on legume growth, N uptake and the proportional dependence of the legume on atmospheric N2. While the published data allow an assessment of various biological, edaphic and environmental factors that affect the response of various legumes to AM inoculation, they also highlight the paucity of quantitative field data and the lack of understanding of the interaction of legume genotype with AM species with respect to legume symbiotic performance.  相似文献   

5.
Arbuscular mycorrhizal (AM) fungi have been shown to induce the biocontrol of soilborne diseases, to change the composition of root exudates and to modify the bacterial community structure of the rhizosphere, leading to the formation of the mycorrhizosphere. Tomato plants were grown in a compartmentalized soil system and were either submitted to direct mycorrhizal colonization or to enrichment of the soil with exudates collected from mycorrhizal tomato plants, with the corresponding negative controls. Three weeks after planting, the plants were inoculated or not with the soilborne pathogen Phytophthora nicotianae growing through a membrane from an adjacent infected compartment. At harvest, a PCR-Denaturing gradient gel electrophoresis analysis of 16S rRNA gene fragments amplified from the total DNA extracted from each plant rhizosphere was performed. Root colonization with the AM fungi Glomus intraradices or Glomus mosseae induced significant changes in the bacterial community structure of tomato rhizosphere, compared to non-mycorrhizal plants, while enrichment with root exudates collected from mycorrhizal or non-mycorrhizal plants had no effect. Our results support that the effect of AM fungi on rhizosphere bacteria would not be mediated by compounds present in root exudates of mycorrhizal plants but rather by physical or chemical factors associated with the mycelium, volatiles and/or root surface bound substrates. Moreover, infection of mycorrhizal or non-mycorrhizal plants with P. nicotianae did not significantly affect the bacterial community structure suggesting that rhizosphere bacteria would be less sensitive to the pathogen invasion than to mycorrhizal colonization. Of 96 unique sequences detected in the tomato rhizosphere, eight were specific to mycorrhizal fungi, including two Pseudomonas, a Bacillus simplex, an Herbaspirilium and an Acidobacterium. One Verrucomicrobium was common to rhizospheres of mycorrhizal plants and of plants watered with mycorrhizal root exudates.  相似文献   

6.
The aim of this experiment was to evaluate the impact of colonization with arbuscular mycorrhizal (AM) fungus Glomus constrictum on the biomass production, flower quality, chlorophyll content, macronutrients and heavy metals content of marigold (Tagetes erecta L.) planted under uncontaminated soil and watered with various rates of sewage water. Sewage water utilization significantly decreased biomass production, characters of flower, nutrient concentration and rates of mycorrhizal colonization of mycorrhizal (M) and non-mycorrhizal (NM) marigold as compared to control untreated plants especially at the higher rates, but the reduction rate was proportionally higher in non-AM treatments. Mycorrhizal plants had significantly greater yield, relative chlorophyll content, leaf area, flower quality and element (P, N, K and Mg) content compared to non-inoculated marigold plants irrigated with or without sewage water. Furthermore, AM inoculation had highly decreased heavy metal (Zn, Co, Mn, Cu) content in tissues as compared to equivalent non-inoculated plants grown under sewage water application. Growing marigold with AM inoculum can reduce toxicity of heavy metals and enhance biomass production and P uptake. The results support the view that AM have a protective function for the host plant, hence playing a potential function in soil polluted immobilization processes, and thus are of assessing the potential of phytoremediation of heavy metals in sewage water contaminated soil.  相似文献   

7.
ABSTRACT

A pot experiment investigated the response of two maize inbred lines with contrasting root morphology and phosphorus (P) efficiency to inoculation with Glomus mosseae or Glomus etunicatum compared with non-mycorrhizal controls. Soil phosphorus was supplied at rates of 10, 50, and 100 mg P kg ?1 soil. Root length, specific root length, and specific phosphorus uptake of maize line 178 (P-efficient) were significantly higher than of line Hc (P-inefficient). Percentage of root length colonized showed the opposite trend regardless of soil P supply level. The two maize lines did not differ significantly in growth response to mycorrhizal colonization. Root colonization rate decreased with increasing soil phosphorus supply. The beneficial effect of the two AM fungi on plant growth and P uptake was greatest at low soil P level and the responses were negative at high P supply. Mycorrhizal responsiveness also decreased with increasing P supply and differed between the two mycorrhizal fungal isolates.  相似文献   

8.
Abstract: There is no information regarding genotypic variation in essential and nonessential nutrient accumulation of sunflower grown under drought stress with the presence or absence of supplemental silicon (Si) despite the role of this element in improving growth of some cultivars under drought conditions. Accumulation of elements in sunflower cultivars might be important for the genetic improvement of the crop's response to drought. An experiment under controlled conditions was carried out to study the genotypic response of 12 sunflower (Helianthus annuus L.) cultivars to drought and Si and the relationship to the uptake of elements [phosphorus (P), potassium (K), sulfur (S), calcium (Ca), magnesium (Mg), iron (Fe), copper (Cu), zinc (Zn), manganese (Mn), chloride (Cl), molybdenum (Mo), Si, sodium (Na), vanadium (V), aluminum (Al), strontium (Sr), rubidium (Rb), titanium (Ti), chromium (Cr), nickel (Ni), bromine (Br), and barium (Ba)]. This was determined by polarized energy‐dispersive X‐ray fluorescence (PEDXRF). It was observed that uptake of nutrient and nonessential elements by sunflower cultivars were differentiated in response to applied Si and drought stress. Drought stress decreased mineral uptake of all the cultivars, and generally, application of Si under drought stress significantly improved Si, K, S, Mg, Fe, Cu, Mn, Na, Cl, V, Al, Sr, Rb, Ti, Cr, and Ba uptake whereas Zn, Mo, Ni, and Br uptake were not affected.  相似文献   

9.
Arbuscular mycorrhizal (AM) fungi alleviate the unfavorable effects of salinity stress on plant growth. A pot study was conducted to determine the effects of AM fungi and salt on growth and some physiological parameters of Citrus jambheri rootstock. Four levels of salinity (2, 4, 6, and 8 dS m?1 as NaCl) and three mycorrhizal treatments (Glomus etunicatum, Glomus intraradices and non-mycorrhizal (NM) control) were used. As salinity increased, all measured characteristics of plants after 4.5-month growth except Na uptake, proline content, and electrolyte leakage decreased. Shoot dry weight and K uptake were significantly higher in G. intraradices-colonized seedlings than NM controls at all salinity levels. Root dry weight and shoot P uptake were significantly higher in G. etunicatum-colonized seedlings than NM controls at all salinity levels. G. intraradices-colonized seedlings had significantly higher proline content than NM controls and G. etunicatum-colonized seedlings at salinity levels of 4, 6 and 8 dS m?1. The electrolyte leakage percentage was significantly lower in G. intraradices-colonized seedlings than NM controls at all salinity levels. The data demonstrated that mycorrhizal citrus seedlings exhibited greater tolerance to salt stress than NM seedlings and the enhanced proline content seems to be one of the mechanisms involved.  相似文献   

10.
Summary The kinetics of Zn absorption were studied in mycorrhizal (Glomus macrocarpum) and non-mycorrhizal roots of corn (Zea mays L.) at pH 6.0 at Zn concentrations of 75 mol to 1.07 mol m-3. Five concentration-dependent phases of Zn absorption were recognized; phase 0 (1.5–4.0 mmol m-3) was linear but the other four phases (4.0 mmol to 1.07 mol m-3) obeyed Michaelis-Menten kinetics. At low concentrations (less than 4 mmol m-3), sigmoidal kinetics of Zn absorption were observed. The absorption of Zn by mycorrhizal maize was greater at low concentrations but decreased at higher levels. This appeared to be a result of a higher maximal uptake rate in phase 1 and lower K m values in the subsequent phases. Kinetic models yielding continuous isotherms could not account for the observed multiphasic pattern.Research paper no. 6820 through the Director, Experiment Station, G.B. Pant University of Agriculture and Technology, Pantnagar 263 145, UP, India  相似文献   

11.
The effect of salinity on the efficacy of two arbuscular mycorrhizal fungi, Glomus fasciculatum and G. macrocarpum, alone and in combination was investigated on growth, development and nutrition of Acacia auriculiformis. Plants were grown under different salinity levels imposed by 0.3, 0.5 and 1.0 S m-1 solutions of 1 M NaCl. Both mycorrhizal fungi protected the host plant against the detrimental effect of salinity. The extent of AM response on growth as well as root colonization varied with fungal species, and with the level of salinity. Maximum root colonization and spore production was observed with combined inoculation, which resulted in greater plant growth at all salinity levels. AM fungal inoculated plants showed significantly higher root and shoot weights. Greater nutrient acquisition, changes in root morphology, and electrical conductivity of soil in response to AM colonization was observed, and may be possible mechanisms to protect plants from salt stress.  相似文献   

12.
The potential of interactions between saprophytic and arbuscular mycorrhizal (AM) fungi to improve Eucalyptus globulus grown in soil contaminated with Zn were investigated. The presence of 100 mg kg −1 Zn decreased the shoot and root dry weight of E. globulus colonized with Glomus deserticola less than in plants not colonized with AM. Zn also decreased the extent of root length colonization by AM and the AM fungus metabolic activity, measured as succinate dehydrogenase (SDH) activity of the fungal mycelium inside the E. globulus root. The saprophytic fungi Trametes versicolor and Coriolopsis rigida increased the shoot dry weight and the tolerance of E. globulus to Zn when these plants were AM-colonized. Both saprophytic fungi increased the percentage of AM root length colonization and elevated G. deserticola SDH activity in the presence of all Zn concentrations applied to the soil. In the presence of 500 and 1000 mg kg−1 Zn, there were higher metal concentrations in roots and shoots of AM than in non-AM plants; furthermore, both saprophytic fungi increased Zn uptake by E. globulus colonized by G. deserticola. The higher root to shoot metal ratio observed in mycorrhizal E. globulus plants indicates that G. deserticola enhanced Zn uptake and accumulation in the root system, playing a filtering/sequestering role in the presence of Zn. However, saprophytic fungi did not increase the root to shoot Zn ratio in mycorrhizal E. globulus plants. The effect of the saprophytic fungi on the tolerance and the accumulation of Zn in E. globulus was mediated by its effect on the colonization and metabolic activity of the AM fungi.  相似文献   

13.
Summary Cucumber was grown in a partially sterilized sand-soil mixture with the vesicular-arbuscular mycorrhizal (VAM) fungus Glomus fasciculatum or left uninoculated. Fresh soil extract was places in polyvinyl chloride tubes without propagules of mycorrhizal fungi. Root tips and root segments with adhering soil, bulk soil, and soil from unplanted tubes were sampled after 4 weeks. Samples were labelled with [3H]-thymidine and bacteria in different size classes were measured after staining by acridine orange. The presence of VAM decreased the rate of bacterial DNA synthesis, decreased the bacterial biomass, and changed the spatial pattern of bacterial growth compared to non-mycorrhizal cucumbers. The [3H]-thymidine incorporation was significantly higher on root tips in the top of tubes, and on root segments and bulk soil in the center of tubes on non-mycorrhizal plants compared to mycorrhizal plants. At the bottom of the tubes, the [3H]-thymidine incorporation was significantly higher on root tips of mycorrhizal plants. Correspondingly, the bacterial biovolumes of rods with dimension 0.28–0.40×1.1–1.6 m, from the bulk soil in the center of tubes and from root segments in the center and top of tubes, and of cocci with a diameter of 0.55–0.78 m in the bulk soil in the center of tubes, were significantly reduced by VAM fungi. The extremely high bacterial biomass (1–7 mg C g-1 dry weight soil) was significant reduced by mycorrhizal colonization on root segments and in bulk soil. The incorporation of [3H]-thymidine was around one order of magnitude lower compared to other rhizosphere measurements, probably because pseudomonads that did not incorporate [3H]-thymidine dominated the bacterial population. The VAM probably decreased the amount of plant root-derived organic matter available for bacterial growth, and increased bacterial spatial variability by competition. Thus VAM plants seem to be better adapted to compete with the saprophytic soil microflora for common nutrients, e.g., N and P, compared to non-mycorrhizal plants.  相似文献   

14.
A pot culture experiment was carried out to study the growth of and Cu uptake by maize (Zea mays) inoculated with or without arbuscular mycorrhizal (AM) fungus Acaulospora mellea in sterilized soil with different Cu amounts added (0, 100, 200, 400, 800 mg kg−1). Root colonization rates were significantly lower with the addition of 400 and 800 mg kg−1 Cu. AM inoculation increased shoot dry weights at 200 and 400 mg kg−1 Cu added but showed no effects at other levels, while increased root dry weights at all Cu addition levels except 800 mg kg−1. Compared with the nonmycorrhizal plants, shoot Cu concentrations in mycorrhizal plants were higher when no Cu was added but lower at other levels, while root Cu concentrations were lower at 400 and 800 mg kg−1 Cu added but not affected at other levels. Thus, shoot Cu uptake in mycorrhizal plants increased with no Cu added but decreased at other levels, while mycorrhizal effects on root Cu uptake varied. Compared with nonmycorrhizal controls, Cu uptake efficiency and phytoextraction efficiency in mycorrhizal plants were higher when no Cu was added but lower at other levels, and Cu translocation efficiency was lower at all Cu addition levels. AM inoculation improved shoot and root P nutrition at all Cu addition levels. Soil pH was higher in mycorrhizal treatment than in the control when 200 mg kg−1 or more Cu was added. These results indicate that A. mellea ZZ may be not suitable for Cu phytoextraction by maize, but shows a potential role in phytostabilization of soil moderately polluted by Cu.  相似文献   

15.
Phosphorus (P) behavior and its efficiency in mycorrhizal plants are of great importance. The objective was to evaluate the behavior of soil labeled P absorbed by different mycorrhizal wheat genotypes subjected to saline water. Three wheat genotypes including cultivar Kavir, the local cultivar Roshan, and the mutated line Tabasi T-65-7-1 were inoculated with different species of arbuscular mycorrhiza (AM) including Glomus etunicatum, G. mosseae, and G. intraradices. Plants were irrigated using saline water (electrical conductivity of 13.87 dS m?1). The experiment was a factorial with 12 treatments and three replications under greenhouse conditions. Wheat genotypes and AM species significantly affected plant dry weight, specific activity, and total plant activity (P?=?0.01). A maximum of 1.49-fold increase in specific activity or P uptake per gram of plant dry matter and 3.53-fold increase in plant activity or plant total P uptake resulted by G. etunicatum as compared with control.  相似文献   

16.
In the symbiosis between nodulated legume roots and arbuscular mycorrhizal (AM) fungi, the C and N economy can be influenced by the source of N-supply from either AM-derived NH4+ uptake or nodule-derived biological nitrogen fixation (BNF). This relationship was investigated in terms of NH4+ supply and BNF by the two symbionts. Nodulated Phaseolus vulgaris seedlings with and without AM, were hydroponically grown with either 0 N or 1 mM NH4+ supply. Plants were harvested at 30 days after emergence and measurements were taken for biomass, N2 fixation, photosynthesis, CO2 and O2 root respiration, calculated C and N economy. AM roots had higher NH4+ uptake and this was associated with the suppression of BNF and nodule growth. The higher NH4+ uptake in AM roots occurred with lower root maintenance respiration, compared to when N was derived from BNF. There was also an increase in the below-ground sink strength of NH4+ fed AM roots compared to NH4+ fed non-AM roots, as evidenced by the increases in root CO2 and O2 respiration and photosynthetic stimulation. These results indicate that although the AM root had higher total below-ground respiratory costs during NH4+ nutrition, there were lower respiratory C costs associated with N derived from AM symbionts in comparison to N from BNF.  相似文献   

17.
A greenhouse experiment was conducted in a red sandy loam soil (Alfisol) to study the responses of arbuscular mycorrhizal (AM) fungus Glomus intraradices Schenck & Smith inoculated (M+) and uninoculated (M−) maize (Zea mays L) plants exposed to various levels of P (15 and 30 mg kg−1) and Zn (0, 1.25, and 2.5 mg kg−1). Roots and shoots were sampled at 55 and 75 days after sowing and assessed for their nutritional status, root morphology, and root cation exchange capacity (CEC) besides grain quality. Mycorrhizal plants had longer and more extensive root systems than nonmycorrhizal plants, indicating that M+ plants are nutritionally rich, especially with P, which directly assisted in the proliferation of roots. Further, root CEC of M+ plants were consistently higher than those of M− plants, suggesting that mycorrhizal colonization assists in the acquisition of nutrients from soil solution. Mycorrhizal inoculated plants had significantly (P ≤ 0.01) higher P and Zn concentrations in roots, shoots, and grains, regardless of P or Zn levels. The available Zn and P status of AM fungus-inoculated soils were higher than unioculated soils. The data suggest that mycorrhizal symbiosis improves root morphology and CEC and nutritional status of maize plants by orchestrating the synergistic interaction between Zn and P besides enhancing soil available nutrient status that enables the host plant to sustain zinc-deficient conditions.  相似文献   

18.
Previous studies reported manure application to eroded Portneuf silt loam soil (Coarse-silty, mixed, superactive, Durinodic Xeric Haplocalcid) improved dry bean (Phaseolus vulgaris L., cv. Viva) yield to levels of topsoil. These yield increases only correlated with whole-plant zinc (Zn) concentration and soil organic matter. This might be related to enhanced arbuscular mycorrhizal (AM) colonization stimulated by manure application. A greenhouse study with dry bean suggested a relationship between manure application, increased AM colonization, and whole-plant Zn uptake, while field studies with wheat (Triticum aestivum L.) and sweet corn (Zea mays L.) did not. To clarify the apparent contradiction of manure application on AM relationships, the present field study with dry bean and sweet corn was conducted in subsoils on the same experimental site established in 1991 and used in previous studies. The existing rotation also allowed the study of the effects of previously fallowed versus wheat cropped subsoils on yield, AM colonization and nutrition of dry bean and sweet corn. Average mycorrhizal root colonization in dry bean was greater on unamended than on manure-amended soils but was not related to increases in yield, Zn concentration, or Zn uptake. Average colonization of sweet corn roots was generally greater in unamended than manure-amended soils, but yields were greater in manure-amended soils. Colonization of sweet corn roots measured over time was consistently greater in subsoils previously cropped to wheat than fallowed, but yields were similar. Previous wheat-cropping resulted in leveling off of colonization beginning 7 July (second sampling) in dry bean, while previous fallow resulted in continuously increasing colonization throughout the five sampling periods. Bean yields were greater on subsoils previously cropped than fallowed; thus yields were generally not related to AM colonization. Results of our study confirm other field results where AM colonization was greater in unamended than manure-amended soils and in cropped than in fallowed soils. Any yield increases observed were not closely related to AM colonization.  相似文献   

19.
A greenhouse experiment was conducted to study the effect of mycorrhizal colonization by Gigaspora margarita, Glomus intraradices, and Acaulospora laevis on nutrient uptake of K, Ca, Mg, Cu, Zn, Fe, and Mn by Astragalus sinicus L. in soils spiked with lanthanum at five rates (0, 1, 5, 10, and 20 mg kg−1). Lanthanum application significantly decreased the concentrations of K, Ca, Mg, Cu, Zn, and Fe in shoots and the concentrations of Cu and Zn in roots. Mycorrhizal treatments markedly improved uptake of nutrients, and these results are important since nutrient deficiency often occurs in contaminated sites.  相似文献   

20.
The bioavailability of heavy metals (Cd, Zn, Pb, Cu) and the abundance of arbuscular mycorrhiza (AM) were studied in two agricultural fields close to a Pb-Zn smelter and three fields outside the pollution zone all cultivated with maize (Zea mays L.). Metal extractability with ethylenediaminetetraacetic acid (EDTA)-NH4OAc and Ca(NO3)2, plant metal uptake, and mycorrhizal parameters (spore number, root colonization) were assessed at two growth stages (six-leaf and maturity). Despite regular liming, the availability of Cd, Zn, and Pb was markedly higher in the two metal-polluted fields than in the three uncontaminated fields. However, the AM abundance was not correlated with metal availability. Root colonization and spore numbers in the metal polluted fields were relatively high, though at plant maturity the former was significantly lower than in one of the uncontaminated fields. The very low AM abundance in the two other unpolluted fields was related to other factors, particular soil and plant P status and soil pH. AM root colonization did not substantially prevent plant metal accumulation, since the metal concentrations in maize grown on the polluted fields strongly exceeded normal values, and for Cd and Pb reached the limits of toxicity for animal feed.  相似文献   

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