共查询到20条相似文献,搜索用时 609 毫秒
1.
Yunsheng Lou Lixuan Ren Zhongpei Li Huanyou Cheng Taolin Zhang 《Water, air, and soil pollution》2011,219(1-4):501-506
As one of the important problems in global change, elevated ultraviolet-B (UV-B) radiation induced by the depletion of stratospheric ozone layer has received more and more attentions around the world. Field experiment with barley was conducted to investigate the effects of elevated UV-B radiation on microbial biomass carbon and nitrogen in rhizosphere and nonrhizosphere soil. The experiment was designed with two UV-B radiation levels, i.e., elevated (E, simulating 25% stratospheric ozone depletion) and ambient (A, control), and performed at the Station of Agricultural Meteorology, Nanjing University of Information Science and Technology, Nanjing, China. Compared with the control, elevated UV-B radiation significantly depressed shoot biomass by 13.2?C42.6% and root biomass by approximately 50% from jointing to ripening stage. Elevated UV-B radiation significantly increased microbial biomass C and N in nonrhizosphere soil in most cases, but significantly decreased microbial biomass C and N in rhizosphere soil. Further researches are needed to elucidate whether the above findings are connected with the changes in composition and amount of root exudates induced by elevated UV-B radiation, which can mainly affect the dynamics of soil microbial biomass. 相似文献
2.
Robert W. Parmelee Joan G. Ehrenfeld Robert L. Tate III 《Biology and Fertility of Soils》1993,15(2):113-119
Summary We investigated the effects of pitch pine seedling roots on extractable N, microbial growth rate, biomass C and N, and nematodes and microarthropods in microcosms with either organic (41% C, 1.14% N) or mineral (0.05% C, 0.01% N) horizon soils of a spondosol. Root quantity was manipulated by varying plant density (0, 1, 2, or 4 seedlings) and rhizosphere soil was separated from non-rhizosphere soil by a 1.2 m mesh fabric. In the rhizosphere of organic soil horizons, moisture, microbial growth rate, biomass C and N, and extractable N declined as root density was increased, but there was little effect on nematodes or microarthropods. High levels of extractable N remained after 5 months, suggesting that N mineralization was stimulated during the incubation. In the rhizosphere of mineral soil horizons, microbial growth rate, and nematode and microarthropod abundances increased at higher root density, and in the absence of roots faunal abundance approached zero. Faunal activity was concentrated in the rhizosphere compared to non-rhizosphere soil. In organic soil horizons, roots may limit microbial activity by reducing soil moisture and/or N availability. However, in mineral soil horizons, where nutrient levels are very low, root inputs can stimulate microbial growth and faunal abundance by providing important substrates for microbial growth. Our results demonstrate a rhizosphere effect for soil fauna in the mineral soil, and thus extends the rhizosphere concept to components of the soil community other than microbes for forest ecosystems. Although our results need to be verified by field manipulations, we suggest that the effects of pine roots on nutrient cycling processes in coniferous forests can vary with soil nutrient content and, therefore, position in the soil profile. 相似文献
3.
Xuefeng Shen Jianmin Li Liusheng Duan Zhaohu Li A. Egrinya Eneji 《Journal of plant nutrition》2013,36(10):1731-1743
The objective of this study was to determine if treatment with silicon (Si) may improve nutrient uptake by soybean under ultraviolet-B (UV-B) radiation stress. Soybean (Glycine max L.) cultivars, ‘Kennong 18’ (K 18) and ‘Zhonghuang 13’ (ZH 13), were grown in hydroponic cultures under ambient and supplemental levels of ultraviolet-B (UV-B, 280–315 nm) with and without Si. Supplemental UV-B radiation simulating 30% stratospheric ozone depletion significantly decreased plant biomass by 74.9 to 135.6%, increased leaf nitrogen (N) and phosphorus (P) by 9% and 16%, respectively, decreased leaf magnesium (Mg) contents by 9%, and calcium (Ca) by 24%. UV-B radiation caused a substantial increase in the allocation of P, potassium (K) and Ca to roots compared with stem and leaves, presumably to ensure sustained nutrient uptake under the stress. Silicon application improved the uptake of P and Mg by 11%, which favored the partitioning of dry mass to shoots under UV-B radiation and the allocation of tissue P and Ca to roots. The overall changes due to Si supported a reasonable increase in dry mass of the ‘K 18’ cultivar. 相似文献
4.
Considerable progress has been made during the last decade towards understanding and quantifying the input and turnover of plant carbon in the rhizosphere. This was made possible by the development (partially by the authors) and combination of appropriate new methods, such as:
- –homogeneous labelling of whole plants with 14C
- –distinction between root and microbial respiration
- –separation of soil zones of known distances from the roots
- –determination of microbial soil biomass.
- –release of organic plant carbon into the soil by growing roots
- –utilization of this plant carbon by the microbial biomass in the rhizosphere
- –related influence on the turnover of soil organic matter, and
- –spatial range of such root influence in the soil.
5.
Mario Schenck zu Schweinsberg‐Mickan Rainer Georg Jörgensen Torsten Müller 《植物养料与土壤学杂志》2012,175(5):750-760
A greenhouse rhizobox experiment was carried out to investigate the fate and turnover of 13C‐ and 15N‐labeled rhizodeposits within a rhizosphere gradient from 0–8 mm distance to the roots of wheat. Rhizosphere soil layers from 0–1, 1–2, 2–3, 3–4, 4–6, and 6–8 mm distance to separated roots were investigated in an incubation experiment (42 d, 15°C) for changes in total C and N and that derived from rhizodeposition in total soil, in soil microbial biomass, and in the 0.05 M K2SO4–extractable soil fraction. CO2‐C respiration in total and that derived from rhizodeposition were measured from the incubated rhizosphere soil samples. Rhizodeposition C was detected in rhizosphere soil up to 4–6 mm distance from the separated roots. Rhizodeposition N was only detected in the rhizosphere soils up to 3–4 mm distance from the roots. Microbial biomass C and N was increased with increasing proximity to the separated roots. Beside 13C and 15N derived from rhizodeposits, unlabeled soil C and N (native SOM) were incorporated into the growing microbial biomass towards the roots, indicating a distinct acceleration of soil organic matter (SOM) decomposition and N immobilization into the growing microbial biomass, even under the competition of plant growth. During the soil incubation, microbial biomass C and N decreased in all samples. Any decrease in microbial biomass C and N in the incubated rhizosphere soil layers is attributed mainly to a decrease of unlabeled (native) C and N, whereas the main portion of previously incorporated rhizodeposition C and N during the plant growth period remained immobilized in the microbial biomass during the incubation. Mineralization of native SOM C and N was enhanced within the entire investigated rhizosphere gradient. The results indicate complex interactions between substrate input derived from rhizodeposition, microbial growth, and accelerated C and N turnover, including the decomposition of native SOM (i.e., rhizosphere priming effects) at a high spatial resolution from the roots. 相似文献
6.
养殖废水灌溉下施用生物质炭和果胶对土壤养分和重金属迁移的影响 总被引:1,自引:0,他引:1
7.
Yan He Jianming Xu Xiaofei Lv Zhaohui Ma Jianjun Wu Jiachun Shi 《Soil biology & biochemistry》2009,41(9):1807-1813
To understand root–soil–microbe interactions in rhizo-depletion of xenobiotics, we conducted a glasshouse study using specially designed laminar rhizoboxes which allow intact layers of near- (1–5 mm) and far- (>5 mm) rhizosphere soil to be harvested separately from root surfaces without the removal of the root material itself. Plant (Lolium perenne L.) seedlings were grown for 90 days in a soil treated with PCP at 20 and 50 mg kg−1. Changes in PCP depletion, soil microbial biomass and community structure (as indicated by phospholipid fatty acids (PLFAs) profiles) with increasing distance from the root surfaces were then assessed after harvesting. Surprisingly, depletion of PCP in the planted rhizoboxes exhibited a nonlinear dependence on the distance to root surfaces, with the most rapid loss in the 2 or 3 mm near-rhizosphere layers, contrasting to the well-known linear gradient of root exudates and mineral nutrients etc. (generally, the extent gradually decreased with increasing distance from the root surface). Soil microbial biomass carbon, however, decreased linearly as expected with increasing distance from the roots. The microbial community structures as indicated by PLFA profiles showed distance-dependent selective enrichment of competent species that may be responsible for efficient PCP depletion. The results suggest that root exudates induced modifications of microbial communities in the PCP contaminated rhizosphere and spatially modified the dominant species within these communities, resulting in the nonlinear PCP depletion pattern. 相似文献
8.
The utilization of plant- and soil-C by the microbial biomass in the rhizosphere of maize plants was investigated as a function of root proximity. The plants were cultivated in pots with divided root chambers and their shoots supplied with 14CO2 for 23 days. Subsequently the individual soil zones were analyzed for organic C, 14C, biomass C and biomass 14C. Plant roots induced a 197% increase in microbial biomass and a 5.4% decrease in soil organic C compared with an 1.2% decrease in the unplanted control soil. The contributions of plant- and soil-C to this increased microbial growth amounted to 68% and 32% respectively. Biomass-14C corresponded to 1.6% of the total photosynthetically fixed 14C, to about 15% of the organic 14C-input into the rhizosphere and to 58% of the plant carbon remaining in soil after the removal of roots. 20% of this biomass-14C was found outside the immediate root zone. These results demonstrate that growing roots are a significant C-source for the microbial biomass and render an additional fraction of soil-C available to microbial utilization. The efficiency of C-utilization by the rhizosphere biomass is lower than values obtained with liquid cultures in laboratory experiments. The supply of plant-C to the microbial biomass outside the immediate root vicinity indicates that the overall volume of the maize rhizosphere is greater than what has been supposed so far. 相似文献
9.
Production of root-derived material and associated microbial growth in soil at different nutrient levels 总被引:9,自引:0,他引:9
R. Merckx A. Dijkstra A. den Hartog J. A. van Veen 《Biology and Fertility of Soils》1987,5(2):126-132
Summary Maize plants were grown for 42 days in a sandy soil at two different mineral nutrient levels, in an atmosphere containing 14CO2. The 14C and total carbon contents of shoots, roots, soil and soil microbial biomass were measured 28, 35 and 42 days after germination. Relative growth rates of shoots and roots decreased after 35 days at the lower nutrient level, but were relatively constant at the higher nutrient level. In the former treatment, 2% of the total 14C fixed was retained as a residue in soil at all harvests while at the higher nutrient level up to 4% was retained after 42 days. Incorporation of 14C into the soil microbial biomass was close to its maximum after 35 days at the lower nutrient level, but continued to increase at the higher level. Generally a good agreement existed between microbial biomass, 14C contents and numbers of fluorescent pseudomonads in the rhizosphere. Numbers of fluorescent pseudomonads in the rhizosphere were maximal after 35 days at the lower nutrient level and continued to increase at the higher nutrient level. The proportions of the residual 14C in soil, incorporated in the soil microbial biomass, were 28% to 41% at the lower nutrient level and 20%6 – 30% at the higher nutrient level. From the lower nutrient soil 18%6 – 52%6 of the residual soil 14C could be extracted with 0.5 N K2SO4, versus 14%6 – 16% from the higher nutrient soil.Microbial growth in the rhizosphere seemed directly affected by the depletion of mineral nutrients while plant growth and the related production of root-derived materials continued. 相似文献
10.
Rapid nitrogen(N) transformations and losses occur in the rice rhizosphere through root uptake and microbial activities. However,the relationships between rice roots and rhizosphere microbes for N utilization are still unclear. We analyzed different N forms(NH+4,NO-3, and dissolved organic N), microbial biomass N and C, dissolved organic C, CH4 and N2O emissions, and abundance of microbial functional genes in both rhizosphere and bulk soils after 37-d rice growth in a greenhouse pot experiment. Results showed that the dissolved organic C was significantly higher in the rhizosphere soil than in the non-rhizosphere bulk soil, but microbial biomass C showed no significant difference. The concentrations of NH+4, dissolved organic N, and microbial biomass N in the rhizosphere soil were significantly lower than those of the bulk soil, whereas NO-3in the rhizosphere soil was comparable to that in the bulk soil. The CH4 and N2O fluxes from the rhizosphere soil were much higher than those from the bulk soil. Real-time polymerase chain reaction analysis showed that the abundance of seven selected genes, bacterial and archaeal 16 S rRNA genes, amoA genes of ammonia-oxidizing archaea and ammonia-oxidizing bacteria, nosZ gene, mcrA gene, and pmoA gene, was lower in the rhizosphere soil than in the bulk soil, which is contrary to the results of previous studies. The lower concentration of N in the rhizosphere soil indicated that the competition for N in the rhizosphere soil was very strong, thus having a negative effect on the numbers of microbes. We concluded that when N was limiting, the growth of rhizosphere microorganisms depended on their competitive abilities with rice roots for N. 相似文献
11.
Katarzyna Hrynkiewicz Christel Baum Peter Leinweber 《European Journal of Soil Biology》2009,45(2):168-175
Low supply of the nutrients nitrogen (N) and phosphorus (P) limit plant growth and spreading, and increase the plant-microbial nutrient competition in subarctic and arctic regions. We investigated the mycorrhizal community structure of a polar shrub willow (Salix polaris) and the microbial turnover in its rhizosphere to explore the adaptation of a mycorrhizal plant in the subarctic tundra. The ectomycorrhizal colonisation ranged from 35 to 64% of the fine root tips and decreased with an increasing soil C/N ratio. In total, 16 ectomycorrhizal morphotypes were found under S. polaris (eight to 13 morphotypes per site, five morphotypes at all four sites). Cenococcum sp. was the most common EM fungus (32% of the ectomycorrhizal fine roots). The abundance of Cenococcum sp. increased with an increasing organic matter content and N/P ratio in the soil. Arbuscular mycorrhizal colonisation of S. polaris was absent or less than 1% of the fine root length. Microbial biomass P accounted for 21–75% of the organic soil P and 6–49% of the total soil P. Microbial biomass P, alkaline and acid phosphatase activities in the rhizosphere increased with increasing soil N concentration. We conclude that a higher N supply decreases the diversity in the mycorrhizal community on polar willows and increases the role of P turnover from the soil microbial biomass for the nutrient supply. 相似文献
12.
Astrid Appuhn 《Soil biology & biochemistry》2006,38(9):2557-2564
Perennial rye grass (Lolium perenne) was grown in a greenhouse pot experiment on seven soils to answer the question whether the microbial colonisation of roots is related to existing differences in soil microbial indices. The soils were similar in texture, but differed considerably in soil organic matter, microbial biomass, and microbial community structure. Ergosterol and fungal glucosamine were significantly interrelated in the root material. This ergosterol was also significantly correlated with the average ergosterol content of bulk and rhizosphere soil. In addition, the sum of fungal C and bacterial C in the root material revealed a significant linear relationship with microbial biomass C in soil. The colonisation of roots with microorganisms increased apparently with an increase in soil microbial biomass. In the root material, microbial tissue consisted of 77% fungi and 23% bacteria. In soil, the fungal dominance was slightly, but significantly lower, with 70% fungi and 30% bacteria. Fungal glucosamine in the root material was significantly correlated with that in soil (r=0.65). This indicates a close relationship between the composition of dead microbial remains in soil and the living fraction in soil and root material for unknown reasons. 相似文献
13.
Mario Schenck zu Schweinsberg-Mickan Rainer Georg Joergensen 《Soil biology & biochemistry》2010,42(6):910-918
A greenhouse rhizobox experiment was carried out to quantify the incorporation of 13C- and 15N-labelled rhizodeposits into different soil pools, especially into the rhizosphere microbial biomass, with increasing distances to the root surface of Lolium perenne. Five layers were analysed over 0-4.2 mm distance to an artificial root surface. C and N derived from rhizodeposition were 4.2% of total C and 2.8% of total N in soil at 0-1.0 mm distance and decreased rapidly with increasing distance. Microbial biomass C and N increased significantly towards the roots. At 0-1.0 mm distance microbial biomass C and N accounted for 66% and 29% of C and N derived from rhizodeposition, respectively. These percentages declined with increasing distance to the roots, but were still traceable up to 4.2 mm distance. Only small amounts of root released C and N were found in the 0.05 M K2SO4-extractable fraction. Extractable C and N derived from rhizodeposition varied around means of 4% of total C and N derived from rhizodeposition and increased only marginally with increasing distance to the roots. C derived from rhizodeposition in the non-extractable soil organic matter increased from 65 to 89% of total C derived from rhizodeposition at 0-3.4 mm distance. Conversely, microbial biomass C derived from rhizodeposition decreased from 33 to 4%. N derived from rhizodeposition in the non-extractable soil organic matter increased from 61 to 79% of total N derived from rhizodeposition at 0-2.6 mm distance, followed by a decline to roughly 55% in the two outer layers. Microbial biomass N decreased from 37 to 16% at 0-2.6 mm distance, followed by an increase to roughly 41% in the two outer layers. The C/N ratio of total C and N derived from rhizodeposition as well as that of extractable C and N derived from rhizodeposition increased with increasing distance to the roots to values above 30. In contrast, the C/N ratio of incorporated rhizodeposition C and N into the microbial biomass decreased to values less than 5 at 2.6-4.2 mm distance. The data indicate differential microbial response to C and N derived from rhizodeposition at a high spatial resolution from the root surface. The turnover of C and N derived from rhizodeposition in the rhizosphere as a function of the distance to the root surface is discussed. 相似文献
14.
15.
《Applied soil ecology》2011,47(3):341-346
We examined acid phosphatase activity (APA), N mineralization and nitrification rates, available N and P, and microbial biomass C, N and P in rhizosphere and bulk soils of 18-year-old Siberian elm (Ulmus pumila), Simon poplar (Populus simonii) and Mongolian pine (Pinus sylvestris var. mongolica) plantations on a nutrient-poor sandy soil in Northeast China. The main objective was to compare the rhizosphere effects of different tree species on N and P cycling under nutrient-deficient conditions. All tree species had the similar pattern but considerably different magnitude of rhizosphere effects. The APA, potential net N mineralization and nitrification rates increased significantly (by 27–60%, 110–188% and 106–142% respectively across the three species) in rhizosphere soil compared to bulk soil. This led to significantly higher Olsen-P and NH4+-N concentrations in rhizosphere soil, whereas NO3−-N concentration was significantly lower in rhizosphere soil owing to increased microbial immobilization and root uptake. Microbial biomass C and N generally increased while microbial biomass P remained constant in rhizosphere soil relative to bulk soil, indicating the N-limited rather than P-limited microbial growth. Rhizosphere effects on P transformation were most pronounced for Siberian elm, while rhizosphere effects on N transformation were most pronounced for Mongolian pine, implying the different capacities of these species to acquire nutrients. 相似文献
16.
Astrid Appuhn 《Soil biology & biochemistry》2006,38(5):1040-1051
Fifteen plants species were grown in the greenhouse on the same soil and sampled at flowering to obtain rhizosphere soil and root material. In both fractions, the data on fungal and bacterial tissue obtained by amino sugar analysis were compared with the total microbial biomass based on fumigation-extraction and ergosterol data. The available literature on glucosamine concentrations in fungi and on muramic acid concentrations in bacteria was reviewed to prove the possibility of generating conversion values for general use in root material. All microbial properties analysed revealed strong species-specific differences in microbial colonisation of plant roots. The root material contained considerable amounts of microbial biomass C and biomass N, reaching mean levels of 10.9 and 1.4 mg g−1 dry weight, respectively. However, the majority of CHCl3 labile C and N, i.e. 89 and 55% was root derived. The average amount of ergosterol was 13 μg g−1 dry weight and varied between 0.0 for Phacelia roots and 45.5 μg g−1 dry weight for Vicia roots. The ergosterol content in root material of mycorrhizal and non-mycorrhizal plant species did not differ significantly. Fungal glucosamine was converted to fungal C by multiplication by 9 giving a range of 7.1-25.9 mg g−1 dry weight in the root material. Fungal C and ergosterol were significantly correlated. Bacterial C was calculated by multiplying muramic acid by 45 giving a range from 1.7 to 21.6 mg g−1 dry weight in the root material. In the root material of the 15 plant species, the ratio of fungal C-to-bacterial C ranged from 1.0 in mycorrhizal Trifolium roots to 9.5 in non-mycorrhizal Lupinus roots and it was on average 3.1. These figures mean that the microbial tissue in the root material consists on average of 76% fungal C and 24% bacterial C. The differences in microbial colonisation of the roots were reflected by differences in microbial indices found in the rhizosphere soil, most strongly for microbial biomass C and ergosterol, but to some extent also for glucosamine and muramic acid. 相似文献
17.
Calcined attapulgite, a non-swelling clay mineral, has been used as a medium for plant growth when mixed with a nutrient solution in the proportion of 0.95 ml g?1. Attapulgite is an ideal model “soil” for ultrastructural studies, enabling large intact thin sections through root, rhizoplane and soil. Transmission electron micrographs are presented which illustrate the value of attapulgite for in situ studies of rhizosphere populations, for the demonstration of enzyme activities in individual bacteria and for specific staining of extracellular polysaccharide.A standard fumigation-respiration technique widely used for estimating soil microbial biomass is shown to give unreliable results for rhizosphere samples and should not be used to measure microbial biomass in close asssociation with living roots. The addition of a dilute soil suspension to the attapulgite medium caused a stimulation of root growth without any increase in shoot growth. 相似文献
18.
半干旱农田生态系统作物根系和施肥对土壤微生物体氮的影响 总被引:5,自引:2,他引:5
盆栽和大田试验表明,作物根系显著影响土壤微生物体氮的含量。在田间试验条件下,根际土壤微生物体氮比非根际土壤平均高出N54.7μg/g;盆栽试验中,根际土壤微生物体氮平均含量为N77.1±13.6μg/g,而非根际土壤为N65.2±17.0μg/g,差异达显著水平,根际微生物体氮含量为非际根际土壤的1.10~2.04倍。施肥能明显增加土壤微生物体氮含量,但影响程度因肥料种类而不同。秸秆和富含有机物质的厩肥对土壤微生物体氮的影响远大于化学肥料,而且土壤微生物体氮含量随秸秆施用量增加而增加。在红油土上进行的20年长期田间定位试验结果表明,对不施肥和施氮磷处理,0—20cm土层的微生物体氮分别是N102.2和110.4μg/g;在施氮磷的基础上,每公顷配施新鲜玉米秸秆9375kg、18750kg、37500kg和厩肥37500kg时,相应土层微生物体氮分别是N147.5、163.2、286.4和265.3μg/g。培养条件下,当有效能源物质缺乏时,微生物对NH4+-N的同化固定能力远大于NO3--N,但在加入有效能源物质葡萄糖后,微生物对2种形态氮的固定量大幅度增加,且对2种形态氮的固定量趋于一致。 相似文献
19.
20.
玉米植株不同部位还田土壤活性碳、氮的动态变化 总被引:2,自引:1,他引:1
探讨玉米植株不同部位腐解对还田土壤活性碳、 氮动态变化的影响。采用室内培养方法,通过动态监测土壤微生物量碳(SMBC)、微生物量氮(SMBN)、可溶性碳(DOC)和矿质氮含量,研究等量玉米根茬、秸秆、茎及叶4个部位在连续7季还田(秸秆+根茬还田)和不还田土壤(仅根茬还田)中的腐解转化特征。结果表明,秸秆腐解的最初 7 d是土壤活性碳、 氮动态变化的高峰期;腐解期间(62 d)SMBC、SMBN含量表现为添加秸秆始终高于根茬,叶分别在前28 d、14 d内高于茎,后期则低于茎,秸秆介于茎、叶之间;土壤DOC、矿质氮含量为叶>秸秆>茎>根茬;培养结束时,各处理SMBC和矿质氮含量均较起始(0 d)显著提高,DOC含量基本保持不变,SMBN含量显著下降。与不还田土壤相比,还田土壤对新鲜残体的腐解影响不显著,且两者间土壤活性氮组分的差异较碳组分明显。腐解期间土壤活性碳、 氮的动态变化主要取决于各器官碳、 氮等化学组分的差异性,等量秸秆较根茬更有利于补充土壤活性碳、氮数量,土壤活性氮组分对还田土壤的响应较碳组分灵敏。 相似文献