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961.
Xing Shun Song Chun Lan Tiao Kai Shi Wei Hua Mao Joshua Otieno Ogweno Yan Hong Zhou Jing Quan Yu 《Plant Growth Regulation》2006,49(1):85-93
In order to clarify the response of antioxidant systems in various cellular organelles to photo-oxidative stress, the activities
of superoxide dismutase (SOD) and enzymes of the ascorbate–glutathione (AsA-GSH) cycle were investigated in chloroplasts,
mitochondria and cytosol of cucumber leaves subjected to methyl viologen (MV) treatment. Photo-oxidation by MV resulted in
significant reductions in net photosynthetic rate (Pn) and increases in the ratio of the quantum efficiency of photosystem
II (PSII),
ΦPSII to that of the quantum efficiency of CO2 fixation (ΦCO2), followed by increased activities of SOD, and a general increase of AsA-GSH cycle enzymes in chloroplasts, mitochondria
and cytosol. These increases were however, most significant in chloroplasts. There were also significant increases in dehydroascorbate
(DHA), reduced glutathione (GSH), and oxidized glutathione (GSSG) except that the content of ascorbate (AsA) in chloroplasts
and cytosol was slightly decreased and little effected, respectively. However, GSSG in mitochondria and GSH in cytosol were
little influenced by the MV treatment. The activity of ascorbate oxidase (AO) in these organelles was independent of the MV
treatment while the activity of l-galactono-1,4- lactone dehydrogenase (GLDH) in mitochondria was slightly inhibited by MV treatment. These results indicate
that disturbance of electron transport in chloroplasts by MV influenced the metabolism of whole cell by a crosstalk signaling
system and that the AsA-GSH cycle played a primary role in sustaining the levels of AsA. 相似文献
962.
Thermotolerance and related antioxidant enzyme activities induced by both heat acclimation and exogenous salicylic acid (SA)
application were studied in grapevine (Vitis vinifera L. cv. Jingxiu). Heat acclimation and exogenous SA application induced comparable changes in thermotolerance, ascorbic acid
(AsA), glutathione (GSH), and hydrogen peroxide (H2O2) concentrations, and in activities of the antioxidant enzymes superoxide dismutase (SOD), peroxidase (POD), glutathione reductase
(GR), ascorbic peroxidase (APX) and catalase (CAT) in grape leaves. Within 1 h at 38 °C, free SA concentration in leaves rose
from 3.1 μg g−1 FW to 19.1 μg g−1 FW, then sharply declined. SA application and heat acclimation induced thermotolerance were related to changes of antioxidant
enzyme activities and antioxidant concentration, indicating a role for endogenous SA in heat acclimation in grape leaves. 相似文献
963.
Nickel-induced Inhibition of Wheat Root Growth is Related to H2O2 Production, but not to Lipid Peroxidation 总被引:1,自引:1,他引:0
Effects of exogenous nickel (Ni: 10 and 200 μM) on growth, mitotic activity, Ni accumulation, H2O2 content and lipid peroxidation as well as the activities of various antioxidative enzymes, such as superoxide dismutase (SOD),
catalase (CAT), ascorbate peroxidase (APX) and glutathione peroxidase (GSH-Px) were investigated in wheat roots. A considerable
Ni accumulation in the roots occurred at both the concentrations. Although Ni at 10 μM did not have any significant effect
on root growth, it strongly inhibited the root growth at 200 μM. Mitotic activity in the root tips was not significantly affected
by exposure of the seedlings to 10 μM Ni; however, it was almost completely inhibited at 200 μM treatment. Ni stress did not
result in any significant changes in CAT and APX activities as well as lipid peroxidation. However, H2O2 concentration increased up to 82% over the control in the roots of seedlings exposed to 200 μM Ni. There was a significant
decline in both SOD (50%) and GSH-Px (20–30%) activities in the roots when the seedlings were treated with 200 μM Ni. The
results indicated that a strong inhibition of wheat root growth caused by Ni stress was not due to enhanced lipid peroxidation,
but might be related to the accumulation of H2O2 in root tissue. 相似文献
964.
Evaluation of CuO oxidation parameters for determining the source and stage of lignin degradation in soil 总被引:1,自引:0,他引:1
The composition of phenols and other aromatic compounds in organic and mineral soil horizons and their respective source vegetation from different climatic zones of the Canadian Prairies were analyzed using CuO oxidation and gas chromatography-mass spectrometry (GC-MS) to investigate the stage of lignin degradation. Parameters based on the CuO oxidation products were calculated for the soils and corresponding vegetation to determine the lignin sources and to monitor the lignin degradation. In addition to the widely used lignin monomer parameters, parameters resulting from lignin-derived phenolic dimers are used for the first time to assess lignin degradation in soils. The composition of lignin-derived phenols (S/V, C/V) in soil closely matches the composition observed in their respective source plants (grass, Aspen, Pine) reflecting the preservation of characteristic lignin patterns in soils. Degradation parameters based on lignin phenols and benzenes derived from tannins or other phenolic biomolecules indicate a progressive degradation from the vegetation to the soil horizons. In addition to commonly used lignin monomer indicators, parameters based on the lignin dimers are applied. Lignin degradation is found to be lowest in the Pine forest, intermediate in the grassland soils and highest in the Aspen-grassland transition soil. Degradation parameters based on non-lignin aromatic derivatives (3,5-dihydroxybenzoic acid, benzenepolycarboxylic acids) demonstrate a similar trend. The lignin from samples in the cooler climate (Black Chernozems) is observed to be more oxidized than in the soils from the warmer climate (Brown Chernozems) suggesting that abiotic processes may be in involved in the alteration of lignin and other phenolic biomolecules in soils. The results indicate that the comparative analysis of CuO oxidation products of soils and source vegetation is a valuable tool to assess the sources and degradation of lignin in soils. 相似文献
965.
Soil Properties and their Spatial Pattern in a Degraded Sandy Grassland under Post-grazing Restoration, Inner Mongolia, Northern China 总被引:10,自引:0,他引:10
In this study, we use classical and geostatistical methods to identify characteristics of some selected soil properties including
soil particle size distribution, soil organic carbon, total nitrogen, pH and electrical conductivity and their spatial variation
in a 5-year recovery degraded sandy grassland after two different grazing intensity disturbance: post-heavy-grazing restoration
grassland (HGR) and post-moderately grazing restoration grassland (MGR), respectively, in Horqin steppe, Inner Mongolia, northern
China. The objective was to examine effect of grazing intensity on spatial heterogeneity of soil properties. One hundred soil
samples were taken from the soil layer 0–15 cm in depth of a grid of 10 m×10 m under each treatment. The results showed that
soil fine fractions (very fine sand, 0.1–0.05 mm and silt + clay, <0.05 mm), soil organic carbon and total nitrogen concentrations
were significant lower and their coefficients of variation significant higher under the HGR than under the MGR. Geostatistical
analysis of soil heterogeneity revealed that soil particle size fractions, organic carbon and total nitrogen showed different
degree of spatial dependence with exponential or spherical semivariograms on the scale measured under HGR and MGR. The spatial
structured variance account for a large proportion of the sample variance in HGR plot ranging from 88% to 97% for soil particle
fractions, organic C and total N, however, except for organic C (88.8%), the structured variance only account for 50% of the
sample variance for soil particle fractions and total N in the MGR plot. The ranges of spatial autocorrelation for coarse-fine
sand, very fine sand, silt + clay, organic C and total N were 13.7 m, 15.8 m, 15.2 m, 22.2 m and 21.9 m in HGR plot, respectively,
and was smaller than in MGR plot with the corresponding distance of 350 m, 144.6 m, 45.7 m, 27.3 m and 30.3 m, respectively.
This suggested that overgrazing resulted in an increase in soil heterogeneity. Soil organic C and total N were associated
closely with soil particle fractions, and the kriging-interpolated maps showed that the spatial distribution of soil organic
C and total N corresponded to the distribution patterns of soil particle fractions, indicating that high degree of spatial
heterogeneity in soil properties was linked to the distribution of vegetative and bare sand patches. The results suggested
that the degree of soil heterogeneity at field scale can be used as an index for indicating the extent of grassland desertification.
Also, the changes in soil heterogeneity may in turn influence vegetative succession and restoration process of degraded sandy
grassland ecosystem. 相似文献
966.
Plant allocation patterns may affect soil C and N storage due to differences in litter quality and the depth of plant C and
N inputs into the soil. We studied the dynamics of dual-labeled (13C/15N) Pinus ponderosa needles and fine roots placed at two soil depths (O and A horizon) in a temperate conifer forest soil during 2 y. Input of
C as fine roots resulted in much more C retained in soil (70.5 ± 2.2% of applied) compared with needle C (42.9 ± 1.3% of applied)
after 1.5 y. Needles showed faster mass loss, rates of soil 13CO2 efflux, and more 15N immobilized into microbial biomass than did fine roots. The larger proportion of labile C compounds initially present in
needles (17% more needle C was water soluble than in fine roots) likely contributed to its shorter C residence time and greater
degree of transformation in the soil. A double exponential decay function best described the rate of 13C loss, with a smaller initial pulse of C loss from fine roots (S1k1) and a slower decay rate of the recalcitrant C pool for fine roots (0.03 y−1) compared with (0.19 y−1) for needles. Soil 13C respiration, representing heterotrophic respiration of litter C, was much more seasonal from the O horizon than from the
A. However, offsetting seasonal patterns in 13C dynamics in the O horizon resulted in no net effect of soil depth on total 13C retention in the soil after 1.5 y for either litter. Almost 90% of applied litter N was retained in the soil after 1.5 y,
independent of litter quality or soil depth. Very small amounts of 13C or 15N (<3% of applied) moved to the horizon above or below the placement depth (i.e., O to A or A to O). Our results suggest that
plant allocation belowground to fine roots results in more C retained and less N mineralized compared with allocation aboveground
to needles, primarily due to litter quality differences. 相似文献
967.
In forest ecosystems the single largest respiratory flux influencing net ecosystem productivity (NEP) is the total soil CO2 efflux; however, it is difficult to make measurements of this flux that are accurate at the ecosystem scale. We examined patterns of soil CO2 efflux using five different methods: auto-chambers, portable gas analyzers, eddy covariance along and two models parameterized with the observed data. The relation between soil temperature and soil moisture with soil CO2 effluxes are also investigated, both inter-annually and seasonally, using these observations/results. Soil respiration rates (R
soil) are greatest during the growing season when soil temperatures are between 15 and 25 °C, but some soil CO2 efflux occurs throughout the year. Measured soil respiration was sensitive to soil temperature, particularly during the spring and fall. All measurement methods produced similar annual estimates. Depending on the time of the year, the eddy covariance (flux tower) estimate for ecosystem respiration is similar to or slightly lower than estimates of annual soil CO2 efflux from the other methods. As the eddy covariance estimate includes foliar and stem respiration which the other methods do not; it was expected to be larger (perhaps 15–30%). The auto-chamber system continuously measuring soil CO2 efflux rates provides a level of temporal resolution that permits investigation of short- to longer term influences of factors on these efflux rates. The expense of building and maintaining an auto chamber system may not be necessary for those researchers interested in estimating R
soil annually, but auto-chambers do allow the capture of data from all seasons needed for model parameterization. 相似文献
968.
The affinity of iron oxides and hydroxides for phosphorus is thought to contribute to phosphorus limitation to net primary
productivity in humid tropical forests on acidic, highly weathered soils. Perennially warm, humid conditions and high biological
activity in these soils can result in fluctuating redox potential that in turn leads to considerable iron reduction in the
presence of labile carbon and humic substances. We investigated the effects of reducing conditions in combination with the
addition of labile carbon substrates (glucose and acetate) and an electron shuttle compound on iron reduction and phosphorus
release in a humid tropical forest soil. Glucose or acetate was added to soils as a single dose at the beginning of the experiment,
and as pulsed inputs over time, which more closely mimics patterns in labile carbon availability. Iron reduction and phosphorus
mobilization were weakly stimulated by a single low level addition of carbon, and the addition of the electron shuttle compound
with or without added carbon. Pulsed labile carbon additions produced a significant increase in soil pH, soluble iron, and
phosphorus concentrations. Pulsed labile carbon inputs also promoted the precipitation of ferrous hydroxide complexes which
could increase the capacity for P sorption, although our results suggest that rates of P solubilization exceeded re-adsorption.
Plant and microbial P demand are also likely to serve as an important sinks for released P, limiting the role of P re-adsorption.
Our results suggest that reducing conditions coupled with periodic carbon inputs can stimulate iron reduction and a corresponding
increase in soil phosphorus mobilization, which may provide a source of phosphorus to plants and microorganisms previously
undocumented in these ecosystems. 相似文献
969.
Hydrologic pathways through soil affect element leaching by determining the relative importance of biogeochemical processes such as sorption and decomposition. We used stable hydrogen isotopes of water (δD) to examine the influence of flowpaths on soil solution chemistry in a mature spruce–hemlock forest in coastal Oregon, USA. Soil solutions (50 cm depth, n = 13) were collected monthly for 1 year and analyzed for δD, major ions and dissolved organic carbon (DOC) and nitrogen (DON). We propose that the variability of δD can be used as an index of flowpath length and contact time. Throughfall variability in δD was much greater than soil solution variability, illustrating that soil solution integrates the variation in inputs. Lysimeters with greater variation in δD presumably have a greater proportion of flow through rapid flowpaths such as macropores. The variation in soil solution δD for individual lysimeters explained up to 53% of the variation in soil solution chemistry, and suggests that flowpaths influence leaching of some constituents. Soil solutions from lysimeters with greater δD variation had higher DOC and DON (r
2 = 0.51 and 0.37, respectively), perhaps because transport via macropores reduces interaction of DOM with the soil matrix. In contrast, nitrate concentrations were highest in lysimeters with a small variation in δD, where long contact time and low DOC concentrations may yield higher net nitrification. Our results demonstrate the utility of stable isotopes to link flowpaths and soil solution chemistry, and illustrate how the spatial complexity of soils can influence ecosystem-level nutrient losses. 相似文献
970.
Lazzaro A Hartmann M Blaser P Widmer F Schulin R Frey B 《FEMS microbiology ecology》2006,58(2):278-292
In this study we compared indicators of Cd bioavailability (water extracts, Lakanen extracts, free ions) and ecotoxicity in forest soils with contrasting physico-chemical characteristics. Soil samples were treated with CdCl(2) solutions (0, 0.1, 1, 10 and 100 mM) and incubated for 30 days. Microbial activity indexes (acid phosphatase, beta-glucosidase, basal respiration) and changes in bacterial community structure using terminal restriction fragment length polymorphism (T-RFLP) fingerprinting were investigated. The Cd concentrations measured ranged from 1% to 37% of the total additions in water extracts, to higher levels in Lakanen extracts. Effects of Cd were observed at bioavailable concentrations exceeding United Nations/European Economic Commission UN/ECE guidelines for total Cd in the soil solution. Basal respiration was the most affected index, while enzymatic activities showed variable responses to the Cd treatments. We also noticed that soils with pH higher than 6.7 and clay content higher than 50% showed inhibition of basal respiration but no marked shift in bacterial community structure. Soils with lower pH (pH <5.8) with less clay content (<50%) showed in addition strong changes in the bacterial community structure. Our results provide evidence for the importance of relating the effects of Cd on the soil communities to soil properties and to bioavailability. 相似文献