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1.
Abstract Soil and hydroponic experiments were carried out to examine the influences of intercropping and nitrogen supply on flavonoid exudation in wheat roots. Both experiments comprising three cropping patterns (wheat intercropped with faba bean, monocropped wheat, and monocropped faba bean) and three N supply levels (deficient, adequate, and excessive) with three replicates in a randomized complete block design. Across two experiments, intercropping increased but N fertilization decreased flavonoids of wheat roots frequently. Intercropping variably increased secretion of naringenin from 0.5 to 1.9 folds (P?<?0.5) in wheat roots at all three N levels, but rarely increased secretion of genistein and hesperetin in wheat at the deficient N level. Intercropped wheat secreted more flavonoids than monocropped wheat at its tillering (60th d) and flowering (95th d) stages; after the flowering stage, however, the differences between intercropping and monocropping were not significant at any N level. Secretion of flavonoids in wheat roots decreased with increased N supply. Interspecies and N supply altered the contents and proportions of flavonoids in wheat root exudations under wheat and faba bean intercropping. These results indicate facilitative root–root interactions and provide insight into cereal promote nodule of legume in intercropping system. 相似文献
2.
Chun-Yi Hu Wen-Sheng Tseng Shu-Ling Hsieh Yo-Chia Chen Shang-Shyng Yang 《Soil biology & biochemistry》2009,41(2):431-434
Here we analyzed carboxymethylcellulase (CMCase; EC 3, 2, 1, 4), one of the key enzymes in the early symbiotic process, in Rhizobium. Specific immunogold labeling of electron microscopy was confirmed in Sinorhizobium fredii BCRC15769, ATCC35423, Sinorhizobium meliloti ATCC9930, and barely detected in Bradyrhizobium japonicum BCRC13528, ATCC10324 and Rhizobium rhizogenes ATCC11325. Non-specific labeling was detected in Rhizobium leguminosarum bv. viceae ATCC10004, Rhizobium leguminosarum bv. trifolii ATCC10328, and Mesorhizobium loti ATCC33669. Treatment of S. fredii BCRC15769 in the early log phase with the flavonoid genistein caused relocalization of CMCase. Together our data suggests a role for CMCase in early symbiosis. 相似文献
3.
Simons AL Renouf M Hendrich S Murphy PA 《Journal of agricultural and food chemistry》2005,53(10):4258-4263
The relationship between chemical structure and gut microbial degradation rates of 14 flavonoids, flavone, apigenin, chrysin, naringenin, kaempferol, genistein, daidzein, daidzin, puerarin, 7,4'-dihydroxyflavone, 6,4'-dihydroxyflavone, 5,4'-dihydroxyflavone, 5,3'-dihydroxyflavone, and 4'-hydroxyflavone, was investigated by anaerobically fermenting the flavonoids with human gut microflora (n = 11 subjects). Degradation rates for the 5,7,4'-trihydroxyl flavonoids, apigenin, genistein, naringenin, and kaempferol, were significantly faster than the other structural motifs. Puerarin was resistant to degradation by the gut microflora. Extensive degradation of flavonoids by gut microflora may result in lower overall bioavailability than those flavonoids that are slowly degraded because rapidly degrading flavonoids are less likely to be absorbed intact. 相似文献
4.
C. Van Nieuwenhove L. Van Holm S. A. Kulasooriya K. Vlassak C. Van Nieuwenhove L. Van Holm 《Biology and Fertility of Soils》2000,31(2):143-149
Azorhizobium caulinodans strongly colonized the rhizosphere of rice plants after incorporation of Sesbania rostrata in a field trial throughout the growing season and during the fallow period until 19 weeks after incorporation of S. rostrata. A. caulinodans became well established in the rhizosphere (7.17 log cfu g–1 dry rice root) and colonized subsequent S. rostrata test plants. Three traditional and three improved high-yielding rice varieties were inoculated with A. caulinodans under gnotobiotic conditions. In none of the combinations did acetylene reduction activity significantly increase. Ethylene
production on colonized rice roots only started after the growth medium had been supplemented with an extra C source (0.1
to 0.25% Na-lactate). This indicates that the bacterial nitrogenase activity is limited by energy supply. Four possible inoculant-carriers
(peat, coir dust, bagasse, rice straw) were compared for long-term survival of the bacterial strain. Independent of the storage
temperature (26 °C or 4 °C), the survival of A. caulinodans in peat and coir dust was very high during a 12-month period (>8 log cfu g–1 dry carrier), whereas the bagasse and rice straw carriers showed a serious decline from 3 months onwards.
Received: 6 April 1999 相似文献
5.
This study aims to determine leaf litter preference, consumption rate, growth rate, food conversion efficiency, and quality
of fecal pellets of two endemic pill millipedes (Arthrosphaera dalyi and Arthrosphaera davisoni) of the Western Ghats of India by laboratory microcosm experiments. Among seven combinations of three plantation leaf litters
offered in 4-day trial, top three preferred combinations were selected for 4-week trial. In 4-week trial, preference of mixed
litter diet was higher than single litter diet, which resulted in enhanced growth as well as food conversion efficiency of
millipedes. Among Hopea
,
Pongamia
, and Areca litters, A. dalyi preferred Hopea + Pongamia, and its consumption was significantly correlated with contents of organic carbon (P < 0.05; r = –0.97) and nitrogen (P < 0.01; r = 0.99), while growth rate with phosphorus content (P < 0.05; r = 0.97) and food conversion efficiency with contents of organic carbon (P < 0.05; r = 0.98) and calcium (P < 0.01; r = –0.99). Among Areca
,
Elettaria
, and Coffea litters, Areca + Elettaria
+ Coffea was most preferred by A. davisoni, which was significantly correlated with organic carbon content (P < 0.05; r = 0.98) and food conversion efficiency with calcium content (P < 0.0001; r = 0.99). The food conversion efficiency, however, was the highest in millipedes fed with Areca
+
Elettaria. The present study demonstrated increased nitrogen and phosphorus contents and decreased phenolic content and C/N ratio in
fecal pellets of pill millipedes fed with plantation litter, and thus, these millipedes play an important role in leaf litter
mineralization and soil enrichment in plantations Western Ghats. 相似文献
6.
Shixue Yin Yuanhua Dong Yangchun Xu Qiwei Huang Qirong Shen 《Biology and Fertility of Soils》2011,47(3):303-313
Rice seedling wilt frequently occurs in upland nurseries under well-aerated conditions and causes considerable economic loss.
Whether the wilt is pathogenic or edaphic is not known. We hypothesize the use of composts to alleviate seedling wilt. The
severity level of upland rice seedling wilt was significantly (p < 0.05) positively correlated with soil pH (r = 0.499; n = 19), but negatively correlated with soil organic matter (r = −0.745), microbial biomass C (r = −0.669), activities of dehydrogenase (r = −0.589), arylsulfatase (r = −0.272), fluorescein diacetate hydrolysis (r = −0.466), and β-glucosidase (r = −0.280). Correlations between severity level and soil inorganic N and exchangeable potassium K were not significant. Contents
of Fe, Zn, Cu, and Mn in healthy seedlings were not significantly (p < 0.05) different from those in infected seedlings. These data suggest that seedling wilts are not associated with nutrient
constraints. Compost amendment at the rate of 3% or above in pot experiments significantly improved seedling growth and reduced
the wilt symptoms. Field trials further showed that aboveground weight of seedlings in compost-amended treatment ranged from
11.5 to 14.9 mg per plant, significantly higher than the range from 6.38 to 12.1 mg per plant in the control treatment; in
addition to rice growth compost significantly increased microbial biomass and enzyme activities of soils. Soil fumigation
significantly increased rice growth and alleviation symptoms in 11 out of 19 soils, suggesting the involvement of pathogens.
It is concluded that upland seedling wilt is a pathogen-associated disease. Probably high soil pH and low soil biochemical
activities may favor pathogen activities. 相似文献
7.
Arylsulfatase activity of microbial biomass in soils as affected by cropping systems 总被引:5,自引:0,他引:5
The impacts of crop rotations and N fertilization on different pools of arylsulfatase activity (total, intracellular, and
extracellular) were studied in soils of two long-term field experiments in Iowa to assess the contibution of the microbial
biomass to the activity of this enzyme. Surface-soil samples were taken in 1996 and 1997 in corn, soybeans, oats, or meadow
(alfalfa) plots that received 0 or 180 kg N ha–1 before corn, and an annual application of 20 kg P ha–1 and 56 kg K ha–1. The arylsulfatase activity in the soils was assayed at optimal pH (acetate buffer, pH 5.8) before and after chloroform fumigation;
microbial biomass C (Cmic) and N (Nmic) were determined by chloroform-fumigation methods. All pools of arylsulfatase activity in soils were significantly affected
by crop rotation and plant cover at sampling time, but not by N fertilization. Generally, the highest total, intracellular,
and extracellular arylsulfatase activities were obtained in soils under cereal-meadow rotations, taken under oats or meadow,
and the lowest under continuous cropping systems.Total, intracellular, and extracellular arylsulfatase activities were significantly
correlated with Cmic (r>0.41, P<0.01) and Nmic (r>0.38, P<0.01) in soils. The averages of specific activity values, i.e., of arylsulfatase activity of the microbial biomass, expressed
per milligram Cmic, ranged from 315 to 407 μg p-nitrophenol h–1. The total arylsulfatase activity was significantly correlated with the intracellular activity, with r values >0.79 (P<0.001). In general, about 45% of the total arylsulfatase activity was extracellular, and 55% was associated with the microbial
biomass in soils, indicating the importance of the microflora as an enzyme source in soils.
Received: 23 April 1998 相似文献
8.
Shipra Singh Anita Pandey Bhaskar Chaurasia Lok Man S. Palni 《Biology and Fertility of Soils》2008,44(3):491-500
The colonization and diversity of arbuscular mycorrhizal fungi (AMF) associated with the rhizosphere of tea [Camellia sinensis (L.) O. Kuntze] growing under ‘natural’ as well as ‘cultivated’ conditions in the Kumaun region of Uttaranchal Himalaya (India),
during the periods of active growth and dormancy were investigated. Root and rhizosphere soil samples, collected from both
the ecosites (natural and cultivated), were monitored for root colonization. While the percent root colonization was quite
high (77.66 ± 4.40 and 86.40 ± 3.02%, in the natural and cultivated tea, respectively) during the period of active growth
in both the ecosites, relatively higher colonization (97.33 ± 0.78 and 98.13 ± 0.80%, in the natural and cultivated tea, respectively)
was recorded during the period of dormancy. The rhizosphere of cultivated tea bushes was found to be dominated by Glomus morhpotypes (88.89% of the total isolates) along with three morphotypes of Acaulospora; occurrence of 35 morphotypes belonging to four genera viz. Acaulospora (11.43%), Gigaspora (11.43%), Glomus (68.57%) and Scutellospora (8.57%) was recorded in the rhizosphere of tea plants from the natural ecosite. A total of 51 AMF morphotypes were detected.
Shannon–Weaver index of diversity was higher (1.80 ± 0.13 and 2.05 ± 0.10 during periods of active growth and dormancy, respectively)
at the species level for the natural ecosite over its counterparts from the cultivated ecosite. Values for the diversity indices
of natural and cultivated ecosites did not show much variation in the period of dormancy. These data suggest that collectively,
various cultural practices negatively affect AMF diversity at the genus level in tea plantations of the colder regions. 相似文献
9.
Amal K. Bandyopadhyay Veena Jain Himmat S. Nainawatee 《Biology and Fertility of Soils》1996,21(3):189-192
A rhizosphere application of NO
inf3
sup-
and/or naringenin affected the Pisum sativum — Rhizobium leguminosarum biovar viciae symbiosis. NO
inf3
sup-
(5 mM) lowered while naringenin raised the nodulation status (nodule numbers and weight) and nodule efficiency (C2H2 reduction activity). However, the inhibitory effect of NO
inf3
sup-
was to some extent alleviated when applied in combination with naringenin. The plant biomass was increased by the application of NO
inf3
sup-
and naringenin, either alone or in combination, while a higher root: shoot ratio was observed only in the naringenin-treated plants. Root flavonoids are known to regulate the expression of nod genes; their high-performance liquid chromatography profile was influenced in different ways by NO
inf3
sup-
and naringenin. 相似文献
10.
The effects of biochar properties on crop growth are little understood. Therefore, biochar was produced from eight feedstocks
and pyrolyzed at four temperatures (300°C, 400°C, 500°C, 600°C) using slow pyrolysis. Corn was grown for 46 days in a greenhouse
pot trial on a temperate and moderately fertile Alfisol amended with the biochar at application rates of 0.0%, 0.2%, 0.5%,
2.0%, and 7.0% (w/w) (equivalent to 0.0, 2.6, 6.5, 26, and 91 t biochar ha−1) and full recommended fertilization. Animal manure biochars increased biomass by up to 43% and corn stover biochar by up
to 30%, while food waste biochar decreased biomass by up to 92% in relation to similarly fertilized controls (all P < 0.05). Increasing the pyrolysis temperature from 300°C to 600°C decreased the negative effect of food waste as well as
paper sludge biochars. On average, plant growth was the highest with additions of biochar produced at a pyrolysis temperature
of 500°C (P < 0.05), but feedstock type caused eight times more variation in growth than pyrolysis temperature. Biochar application rates
above 2.0% (w/w) (equivalent to 26 t ha−1) did generally not improve corn growth and rather decreased growth when biochars produced from dairy manure, paper sludge,
or food waste were applied. Crop N uptake was 15% greater than the fully fertilized control (P < 0.05, average at 300°C) at a biochar application rate of 0.2% but decreased with greater application to 16% below the N
uptake of the control at an application rate of 7%. Volatile matter or ash content in biochar did not correlate with crop
growth or N uptake (P > 0.05), and greater pH had only a weak positive relationship with growth at intermediate application rates. Greater nutrient
contents (N, P, K, Mg) improved growth at low application rates of 0.2% and 0.5%, but Na reduced growth at high application
rates of 2.0% and 7.0% in the studied fertile Alfisol. 相似文献
11.
An experiment was conducted to identify the main nitrogenous compound transported in the xylem sap of soybean plants nodulated with Rhizobium fredii. Soybean (Glycine max L. Merr.) cultivars, wild type Bragg (nod+, fix+) and its nitrate tolerant, hypernodulating mutant ntsll16 (nod++, fix+) were used for this experiment. These soybean plants were inoculated with a slowgrowing rhizobium, Bradyrhizobium japonicum USDAllO or fast-growing rhizobia consisting of a mixture of R. fredii USDA191, USDA193, and USDA-194 and grown in a phytotron under natural light and controlled temperature conditions. Xylem sap was collected from Bragg and ntsll16 plants at the flowering and pod elongation stages. Acetylene reduction activity per plant or per nodule weight was not different between soybean lines and inoculums. The composition of the nitrogenous compounds in the xylem sap was compared between the symbionts, with B. japonicum and R. fredii. At the flowering stage, ureide-N and amide-N accounted for 53 to 70% and 20 to 27% respectively of the total N in the sap collected from the plants inoculated either with B. japonicum or R. fredii. At the pod elongation stage, ureide-N and amide-N accounted for 74 to 85%, and 7 to 19% of total sap N. With the growth of the soybean plants, the ratio of ureide-N in the xylem sap increased. These results suggest that in the case of wild soybean and the hypernodulating mutant line nodulated by R. fredii, ureide is transported as the main nitrogenous compound of fixed nitrogen in the xylem sap in the same way as in plants nodulated with B. japonicum. 相似文献
12.
Donghong Wang Qinghua Shi Xiufeng Wang Min Wei Jinyu Hu Jun Liu Fengjuan Yang 《Biology and Fertility of Soils》2010,46(7):689-696
The effects of cow manure vermicompost on plant growth, metabolite contents, and antioxidant activities of Chinese cabbage
were investigated in pot cultures. Five treatments were designed by mixing vermicompost and soil at ratio of 0:7, 1:7, 2:7,
4:7, 7:0 (w/w). Marketable weight of Chinese cabbage was significantly (p < 0.05) higher in the 2:1 treatment than in the other treatments, while plants grown in the full soil treatment (0:7) showed
the lowest marketable weight (Fig. 1a). Vermicompost application significantly increased the nutrient content of Chinese cabbage leaves (p < 0.05), especially in the 4:7 treatment, with increases in the contents of soluble sugar (Fig. 2a), soluble protein (Fig. 2b), vitamin C (Fig. 3a), total phenols (Fig. 3b), and total flavonoids (Fig. 3c) by 62%, 18%, 200%, 25%, and 17% compared to the full soil treatment, respectively. The antioxidant activities expressed
by 2, 2-Dipenyl-1-picrylhydrazyl-scavenging activity (Fig. 4a), hydroxyl (OH)-scavenging activity (Fig. 4b), and iron (Fe2+)-chelating activity (Fig. 4c) were higher by 92%, 40%, and 36% in the 4:7 than 0:7 the treatment, respectively. Vermicompost application significantly
increased (p < 0.05) the plant contents of 16 essential amino acids (Table 1); the total amino acid content showed the greatest increase in the 4:7 treatment, 90% compared to the full soil treatment. 相似文献
13.
Allolobophora chlorotica exists as two colour morphs, pink and green. Field observations have indicated that the two morphs have ecological preferences
linked to soil moisture: the green morph dominating in wet soils and the pink morph in dry soils. The aim of this laboratory-based
research was to investigate the potential differences in fitness and adaptation to soil-moisture conditions of the two morphs
measured in terms of growth rate, reproductive output and cocoon viability. An initial experiment maintained hatchlings of
both morphs individually under standard culture conditions. On maturation, these were paired (intra-morph), and cocoon production,
viability and incubation time were determined. The green morph had significantly faster (P < 0.01) growth rates than the pink morph. Cocoon production was also significantly greater in the green compared with the
pink morph (3.2 and 1.5 cocoons worm−1 28 days−1, respectively) with corresponding viabilities of 87 and 58%. In a second experiment, the growth rates of pink and green hatchlings
were assessed under wet and dry soils (29 and 21% soil moisture, respectively). The growth of the pink morph was not influenced
significantly (P > 0.05) by soil moisture. In contrast, lower soil-moisture content significantly (P < 0.05) slowed growth and maturation of the green morph. These results support field observations relating to distribution
of the two A. chlorotica colour morphs. We suggest that soil-moisture content may act to isolate these morphs, providing, in extremes, a barrier to inter-morphic
mating. 相似文献
14.
Thirty-five Azospirillum strains (13 strains from plant roots and 22 strains from soils) were isolated from Ishigaki island, Japan, which has a subtropical
climate. These strains were different from each other according to polymerase-chain-reaction band patterns obtained by using
a random primer (OPT-08). Two Azospirillum strains (AZ43 and AZ92-2) were also examined for use in further experiments. Inoculation of lowland rice with these strains
enhanced early growth of rice to various degrees. Inoculation of strains VIII.P1-2, AZ92-2, V.S2-2, and V.P5 in sterilized
soil yielded higher shoot dry weights than the application of 90 μg N g–1 soil without inoculation. Only inoculation with strains AZ92-2 and VIII.P1-2 caused higher N uptake than the application
of 90 μg N g–1 soil. Three strains were selected for the next experiment based on the results of their effect on the early growth of rice.
An investigation was conducted to determine the ability of two indigenous Azospirillum strains (V.S2-2 and VIII.P1-2) and one stock strain (AZ92-2) to promote growth and nutrient-uptake of lowland rice in unsterilized
soil under several levels of N application (0, 80, 160, and 240 mg N pot–1). Inoculation with these strains without N application increased shoot dry weight by 12–15% compared to the uninoculated
treatment. Inoculation with Azospirillum V.S2-2 together with the application of 160 mg N pot–1 resulted in a shoot dry weight as high as that obtained in the treatment with 240 mg N pot–1 without inoculation. Thus, in this former case, the amount of N applied could be reduced by 80 mg pot–1 due to the effect of the microbial inoculum without a significant change in the high, targeted, yield. 相似文献
15.
The impacts of crop rotations and N fertilization on different pools of urease activity were studied in soils of two long-term
field experiments in Iowa; at the Northeast Research Center (NERC) and the Clarion-Webster Research Center (CWRC). Surface
soil samples (0–15 cm) were taken in 1996 and 1997 in corn, soybeans, oats, or meadow (alfalfa) plots that received 0 or 180 kg
N ha–1, applied as urea before corn and an annual application of 20 kg P and 56 kg K ha–1. The urease activity in the soils was assayed at optimal pH (THAM buffer, pH 9.0), with and without toluene treatment, in
a chloroform-fumigated sample and its nonfumigated counterpart. The microbial biomass C (Cmic) and N (Nmic) were determined by chloroform fumigation methods. The total, intracellular, extracellular and specific urease activities
in the soils of the NERC site were significantly affected by crop rotation, but not by N fertilization. Generally, the highest
total urease activities were obtained in soils under 4-year oats–meadow rotations and the lowest under continuous corn. The
higher total activities under multicropping systems were caused by a higher activity of both the intracellular and extracellular
urease fractions. In contrast, the highest values for the specific urease activity, i.e. of urease activity of the microbial
biomass, were found in soils under continuous soybean and the least under the 4-year rotations. Total and extracellular urease
activities were significantly correlated with Cmic (r>0.30* and >0.40**) and Nmic (r>0.39** and >0.44**) in soils of the NERC and CWRC sites, respectively. Total urease activity was significantly correlated
with the intracellular activity (r>0.73***). About 46% of the total urease activity of the soils was associated with the microbial biomass, and 54% was extracellular
in nature.
Received: 25 May 1999 相似文献
16.
Wei-An Lai P. D. Rekha A. B. Arun Chiu-Chung Young 《Biology and Fertility of Soils》2008,45(2):155-164
Benefits from the application of plant growth-promoting bacteria in agriculture largely depend on the complex interactions
between several factors including the nature of fertilizers selected. This study was designed to determine the fine tuning
between the inoculated bacteria and different fertilizers and their effect on the growth of lettuce plants (Lactuca sativa L.). Plant growth promotion by a novel species of the genus Azospirillum, namely A. rugosum IMMIB AFH-6, was tested by biochemical, bioassay, and greenhouse studies. The treatments used in the greenhouse study were;
unfertilized control (Blank), half recommended dose of chemical fertilizer (1/2CF), full recommended dose of chemical fertilizer
(1CF), pig manure fertilizer (PMF), pig manure fertilizer + half recommended dose of chemical fertilizer (PMF + 1/2CF), and
pig manure fertilizer + full recommended dose of chemical fertilizer (PMF + 1CF). All these treatments when inoculated with
A. rugosum IMMIB AFH-6 inoculation were, respectively, In-Blank, In-1/2CF, In-1CF, In-PMF, In-PMF + 1/2CF, and In-PMF + 1CF. Significant
increase in plant biomass and shoot N, P, Ca, and Fe was shown in the In-Blank treatment. Plant growth in soil amended with
PMF and A. rugosum IMMIB AFH-6 was significantly lower than in soil treated with the chemical fertilizer, but inoculation combined with chemical
fertilizer significantly elevated the plant biomass. The In-PMF + 1/2CF treatment showed the highest yield. A. rugosum IMMIB AFH-6 facilitated the accumulation of trace minerals in higher concentrations when PMF was combined with 1CF. To examine
the benefits of inoculation by A. rugosum IMMIB AFH-6, we have proposed a new type of data analysis which considers both biomass and nutrient content of plants. This
new type of analysis has shown the importance of the mineral content of plant. 相似文献
17.
Giancarlo Renella Ute Szukics Loretta Landi Paolo Nannipieri 《Biology and Fertility of Soils》2007,44(2):321-329
The aim of this work was to calculate indices of hydrolase production (Pr) and persistence (Pe) through simple arithmetical
calculations. Changes in acid and alkaline phosphomonoesterase, phosphodiesterase, urease, protease, and β-glucosidase activities
were monitored under controlled conditions in seven soils with a wide range of properties, in which microbial growth was stimulated
by adding glucose and nitrogen. Glucose mineralization was monitored by CO2–C evolution, and microbial growth was quantified by determining the soil adenosine triphosphate (ATP) content. Hydrolase
Pr and Pe indices were numerically quantified by the following relationships: Pr = H / t
H
and Pe = (r / H)Δt, respectively, where H indicates the peak value of each measured hydrolase activity, t
H
is the time of the peak value, r indicates the residual activity value, and Δt is the time interval t
r − t
H, where t
r is the time of the residual activity value. Addition of glucose and N-stimulated soil respiration increased ATP content and
stimulated the production of the measured hydrolase activities in all soils; the measured variable reached a maximum value
and then decreased, returning to the value of the control soil. Apart from β-glucosidase activity, whose activity was not
stimulated by glucose and N addition, the other measured hydrolase activities showed a trend that allowed us to calculate
the Pr and Pe indices using the above-mentioned equations. Acid phosphomonoesterase and protease Pr values were significantly
higher in soils under forest or set aside management; the alkaline phosphomonoesterase and phosphodiesterase Pr values were
generally higher in the neutral and alkaline soils, and the urease Pr values showed no obvious relationships with soil pH
or management. Concerning the persistence of enzyme activities, Pe values of the acid phosphomonoesterase activity were significantly
higher in the acidic soils, and those of urease activity were higher in acidic soils and the Bordeaux neutral soil. No relationships
were observed between Pe values of alkaline phosphomonoesterase, phosphodiesterase, or protease activities and soil pH or
management. The different responses of hydrolases were discussed in relation to soil properties, microbial growth, and regulation
at the enzyme molecular level. 相似文献
18.
Giancarlo Renella Amar M. Chaudri Céline M. Falloon Loretta Landi Paolo Nannipieri Philip C. Brookes 《Biology and Fertility of Soils》2007,43(6):751-758
We investigated Cd, Zn, and Cd + Zn toxicity to soil microbial biomass and activity, and indigenous Rhizobium leguminosarum biovar trifolii, in two near neutral pH clay loam soils, under long-term arable and grassland management, in a 6-month laboratory incubation,
with a view to determining the causative metal. Both soils were amended with Cd- or Zn-enriched sewage sludge, to produce
soils with total Cd concentrations at four times (12 mg Cd g−1 soil), and total Zn concentrations (300 mg Zn kg−1 soil) at the EU upper permitted limit. The additive effects of Cd plus Zn at these soil concentrations were also investigated.
There were no significant differences in microbial biomass C (B
C), biomass ninhydrin N (B
N), ATP, or microbial respiration between the different treatments. Microbial metabolic quotient (defined as qCO2 = units of CO2–C evolved unit−1 biomass C unit−1 time) also did not differ significantly between treatments. However, the microbial maintenance energy (in this study defined
as qCO2-to-μ ratio value, where μ is the growth rate) indicated that more energy was required for microbial synthesis in metal-rich sludge-treated soils (especially
Zn) than in control sludge-treated soils. Indigenous R.
leguminosarum bv. trifolii numbers were not significantly different between untreated and sludge-treated grassland soils after 24 weeks regardless of
metal or metal concentrations. However, rhizobial numbers in the arable soils treated with metal-contaminated sludges decreased
significantly (P < 0.05) compared to the untreated control and uncontaminated sludge-treated soils after 24 weeks. The order of decreasing
toxicity to rhizobia in the arable soils was Zn > Cd > Cd + Zn. 相似文献
19.
Flavonoids, present in fruits, vegetables, and teas, provide beneficial effects for our health. We investigated the effect of a number of flavonoids on tight junction (TJ) barrier integrity in human intestinal Caco-2 cells. Transepithelial electrical resistance (TER; a TJ integrity marker) across cell monolayers was measured in cells incubated with flavonoids for 24 h. Chrysin decreased the TER, indicating a decrease in TJ integrity. Daidzein, hesperetin, naringenin, and morin increased the TER, indicating increased TJ integrity. Luteolin and genistein increased or normalized the TER after a transient decrease. Immunoblot analysis revealed that these changes in TER were caused by modification of the cytoskeletal association and expression of TJ proteins, zonula occludens (ZO)-1, ZO-2, occludin, junctional adhesion molecule-1, and/or claudins. Our results suggest that various flavonoids participate in the regulation of intestinal TJ barrier integrity and that this regulation may partially contribute to the flavonoid-mediated biological effects on our health. 相似文献
20.
Populations of soil-dwelling mites were monitored in monoculture plots of four agroforestry tree species, Gliricidia sepium, Leucaena leucocephala, Dactyladenia barteri and Treculia africana, and compared to those in grass and secondary forest plots in the dry season (December 1993 to January 1994) and in the wet
season (April to June 1994) in southwest Nigeria. Mite populations were very low in all plots during the dry season (500–3000 m–2), compared to those during the wet season (10 000–30 000 m–2). The highest mite population was observed in Gliricidia plots (3 044 m–2) for the dry season and Leucaena plots (30 240 m–2) for the wet season. Mite genera that were dominant in all the experimental plots were Annectacarus, Haplozetes, Machadobelba, Scheloribates and members of the Galumnidae, Dermanyssidae and Parasitidae. The community structure of mites was similar in the soil for
Treculia and Gliricidia plots and for Leucaena and Dactyladenia plots. There were more taxonomic groups of mites under Leucaena than in the other agroforestry plots. Based on the density, diversity and complexity of the mite communities, Leucaena was considered to be better than other agroforestry species in encouraging the growth of mite populations.
Received: 28 April 1998 相似文献