共查询到20条相似文献,搜索用时 31 毫秒
1.
The pathway and ab initio direct kinetics of the decomposition 5-aminotetrazole (5-ATZ) to HN3 and NH2CN was investigated. Reactant, products and transition state were optimized with MP2 and B3LYP methods using 6–311G** and
aug-cc-pVDZ basis sets. The intrinsic reaction coordinate curve of the reaction was calculated using the MP2 method with 6–311G**
basis set. The energies were refined using CCSD(T)/6–311G**. Rate constants were evaluated by conventional transition-state
theory (CVT) and canonical variational transition-state theory (TST), with tunneling effect over 300 to 2,500 K. The results
indicated that the tunneling effect and the variational effect are small for the calculated rate constants. The fitted three-parameter
expression calculated using the CVT and TST methods are and , respectively.
Figure The mechanism of the decomposition process of 5-ATZ to HN3 and NH2CN 相似文献
2.
Effects of common soil anions and pH on the uptake and accumulation of perchlorate in lettuce 总被引:1,自引:0,他引:1
A mechanistic understanding of perchlorate () entry into plants is important for establishing the human health risk associated with consumption of contaminated produce
and for assessing the effectiveness of phytoremediation. To determine whether common soil anions affect uptake and accumulation in higher plants, a series of competition experiments using lettuce (Lactuca sativa L.) were conducted between (50 nM) and (4–12 mM), (1–10 mM), or Cl− (5–15 mM) in hydroponic solution. The effects of (0–5 mM) and pH (5.5–7.5) on uptake were also examined. Increasing in solution significantly reduced the amount of taken up by green leaf, butter head, and crisphead lettuces. Sulfate and Cl− had no significant effects on uptake in lettuce over the concentrations tested. Increasing pH significantly reduced the amount of taken up by crisphead and green leaf lettuces, whereas increasing significantly reduced uptake in butter head lettuce. The inhibition by across all lettuce genotypes suggests that may share an ion carrier with , and the decrease in uptake with increasing pH or provides macroscopic evidence for cotransport across the plasma membrane. 相似文献
3.
Long-term changes in nutrient concentrations of the Changjiang River and principal tributaries 总被引:5,自引:0,他引:5
We present long-term nutrient data on the Changjiang River (Yangtze River) at six hydrological stations and eight principal
tributaries during the period 1958–1985. Three patterns of temporal changes were observed in nitrate
and nitrite : minimal variations in the upper catchment area, rapid increases in the middle watershed towards the end of the 1970s, and
a gradual increase in the lower drainage basin. Prior to the 1970s, the level of throughout the Changjiang River system remained fairly constant. In the 1980s, however, this changed, with the lowest values
in the upper Changjiang changing rapidly to the highest in the middle reaches and then declining slowly but steadily in the
lower courses. Compared to and ammonium and soluble reactive phosphorus (SRP) showed smaller increases or no long-term variations, while dissolved silica (DSi) concentration
generally decreased at most stations. These three patterns of and changes in the Changjiang River system were reflective of the difference in chemical fertilizer use and landscape features
(e.g., slope, soil type and water body area) of the drainage basins of the primary tributaries. The decreases in DSi were
most likely attributed to a reduction in suspended sediment loading due to dam constructions and increasing diatom consumption.
The increase in and with a reduction in DSi concentrations in the Changjiang River could have significant effects on the stoichiometric balance
of nutrients delivered to the East China Sea and the ecosystem in this dynamic region. 相似文献
4.
5.
A novel molecular connectivity index, , based on the adjacency matrix of molecular graphs and novel atomic valence connectivities, , for predicting the molar diamagnetic susceptibilities of organic compounds is proposed. The is defined as: , where and Ei are the atomic valence connectivity and the valence orbital energy of atom i, respectively. A good QSPR model for molar diamagnetic
susceptibilities can be constructed from and using multivariate linear regression (MLR). The correlation coefficient r, standard error, and average absolute deviation
of the MLR model are 0.9918, 5.56 cgs, and 4.26 cgs, respectively, for the 721 organic compounds tested (training set). Cross-validation
using the leave-one-out method demonstrates that the MLR model is highly reliable statistically. Using the MLR model, the
average absolute deviations of the predicted values of molar diamagnetic susceptibility of another 360 organic compounds (test
set) is 4.34 cgs. The results show that the current method is more effective than literature methods for estimating the molar
diamagnetic susceptibility of an organic compound. The MLR method thus provides an acceptable model for the prediction of
molar diamagnetic susceptibilities of organic compounds.
Figure Plot of calculated vs experimental values of molar diamagnetic susceptibilities using the multivariate linear regression (MLR)
model (Eq. 8) 相似文献
6.
The interaction of solvated electrons with DNA results in various types of DNA lesions. The in vitro and in vivo sensitisation of DNA to -induced damage is achieved by incorporation of the electron-affinity radiosensitiser bromodeoxyuridine (BUdR) in place of
thymidine. However, in DNA duplexes containing single-stranded regions (bulged BUdR-DNA), the type of lesion is different
and the efficiency of damage is enhanced. In particular, DNA interstrand crosslinks (ICL) form at high efficiency in bulged
DNA but are not detectable in completely duplex DNA. Knowledge about the processes and interactions leading to these differences
is obscure. Previously, we addressed the problem by applying molecular modelling and molecular dynamics (MD) simulations to
a system of normal (BUdR·A)-DNA and a hydrated electron, where the excess electron was modelled as a localised eˉ(H2O)6 anionic cluster. The goal of the present study was to apply the same MD simulation to a wobble system, containing a pyrimidine–pyrimidine mismatched base pair, BUdR·T. The results show an overall dynamic pattern similar
to that of the motion around normal DNA. However, the number of configuration states when was particularly close to DNA is different. Moreover, in the (BUdR·T)-wobble DNA system, the electron frequently approaches
the brominated strand, including BUdR, which was not observed with the normal (BUdR·A)-DNA. The structure and exchange of
water at the sites of immobilisation near DNA were also characterised. The structural dynamics of the wobble DNA is prone to more extensive perturbations,
including frequent formation of cross-strand (cs) interatomic contacts. The structural deviations correlated with approaching DNA from the major groove side, with sodium ions trapped deep in the minor groove. Altogether, the obtained results
confirm and/or throw light on dynamic-structure determinants possibly responsible for the enhanced radiation damage of wobble
DNA.
Figure The structure of the tightly bound single water-layer between the DNA and the electron (Site-8, five H2O molecules, bold capped sticks); the rest of the “second” shell waters (lines, in atom type colour) surround the ˉ(H2O)6 cluster (yellow, space fill). Orange dashed lines H-bonds; only one of the five molecules from the single H2O layer mediates a single-step H-bond bridge with N7(A8); the other four present a network of two(three)-step H-bond bridges
between DNA/ partner atoms 相似文献
7.
Anaerobic ammonium oxidation (anammox) has recently been recognized as a pathway for the removal of fixed N from aquatic ecosystems.
However, the quantitative significance of anammox in estuarine sediments is variable, and measurements have been limited to
a few estuaries. We measured anammox and conventional denitrification activities in sediments along salinity gradients in
the Chesapeake Bay and two of its sub-estuaries, the Choptank River and Patuxent River. Homogenized sediments were incubated
with 14/15N amendments of , , and to determine relative activities of anammox and denitrification. The percent of N2 production due to anammox (ra%) ranged from 0 to 22% in the Chesapeake system, with the highest ra% in the freshwater portion
of the main stem of upper Chesapeake Bay, where water column concentrations are consistently high. Intermediate levels of relative anammox (10%) were detected at locations corresponding
to tidal freshwater and mesohaline locations in the Choptank River, whereas anammox was not detected in the tidal freshwater
location in the Patuxent River. Anammox activity was also not detected in the seaward end of Chesapeake Bay, where water column
concentrations are consistently low. The ra% did not correlate with accumulation rate in anoxic sediment incubations, but ra% was related to water column concentrations and salinity. Anammox bacterial communities were also examined by amplifying DNA extracted from the upper
Chesapeake Bay sediment with polymerase chain reaction (PCR) primers that are specific for 16S rRNA genes of anammox organisms.
A total of 35 anammox-like sequences were detected, and phylogenetic analysis grouped the sequences in two distinct clusters
belonging to the Candidatus “Scalindua” genus. 相似文献
8.
Factors affecting denitrification in agricultural headwater streams in Northeast Ohio,USA 总被引:2,自引:0,他引:2
As a result of increased anthropogenic nitrogen (N) loading in surface waters of agricultural watersheds, there is enhanced
interest to understand and quantify N removal mechanisms. Denitrification, an important N removal mechanism in aquatic systems,
may contribute to reducing N pollution in agricultural headwater streams. However, the key factors controlling this process
in lotic systems remain unclear. The objective of our study was to examine the factors regulating rates of denitrification
in the sediments of agricultural headwater streams in the mid-western USA. Denitrification rates were variable among streams
and treatments (<0.1–28.0 μg N g AFDM−1 h−1) and on average, were higher than those reported for similar headwater streams. Carbon quantity and quality, and pH had no
effect on denitrification, while temperature and nitrate (
) concentrations had a positive effect on rates of denitrification. Specifically, controlled denitrification following Michaelis-Menten kinetics. We calculated a value of km (1.0 mg -N L-1) that was comparable to other studies in aquatic sediments but was well below the median in-stream concentrations (5.2–17.4 mg -N L−1) observed at the study sites. Despite high rates of denitrification, this removal mechanism is most likely saturated in the agricultural headwater streams we examined, suggesting that these systems are not effective at removing
in-stream N.
Handling editor: D. Ryder 相似文献
9.
The biosorption of metal ions (Cr+3,
, Cu+2, and Ni+2) on two algal blooms (designated HD-103 and HD-104) collected locally was investigated as a function of the initial metal
ion concentration. The main constituent of HD-103 is Cladophora sp., while Spirulina sp. is present significantly in the bloom HD-104. Algal biomass HD-103 exhibited the highest Cu+2 uptake capacity (819 mg/g). This bloom adsorbed Ni+2 (504 mg/g), Cr+3 (347 mg/g), and (168 mg/g). Maximum of Ni+2 (1108 mg/g) is taken by HD-104. This species takes up 306, 202, and 576 mg/g Cr+3, , and Cu+2, respectively. Equilibrium data fit very well to both the Langmuir and the Freundlich isotherm models. The sorption process
followed the Freundlich model better. Pseudo-first-order kinetic model could describe the kinetic data. Infrared (IR) spectroscopic
data were employed to identify the site(s) of bonding. It was found that phosphate and peptide moieties participate in the
metal uptake by bloom HD-103. In the case of bloom HD-104, carboxylate and phosphate are responsible for the metal uptake.
The role of protein in metal uptake by HD-103 was investigated using polyacrylamide gel electrophoresis. 相似文献
10.
Amino azobenzenes are important dyes in the food and textile industry but their application is limited due to their mutagenicity.
Computational modeling techniques were used to help understand the factors responsible for mutagenicity, and several quantitative
structure toxicity relationship (QSTR) models have been derived. HQSTR (hologram QSTR) analyses indicated that different substituents
at sites on both rings contribute to mutagenicity. Fragment parameters such as bond (B) and connectivity(C), as well as donor-acceptor
(DA)-based model provide significant results (q2 = 0.59, r2 = 0.92, ) explaining these harmful effect. HQSTR results indicated that a bulky group at ring “Y” and small group at ring “X” might
help to decrease mutagenicity. 3D-QSTR based on comparative molecular field analyses (CoMFA) and comparative molecular similarity
index analyses (CoMSIA) are also in agreement with HQSTR. The 3D QSTR studies reveal that steric and electrostatic field effects
have a strong relationship with mutagenicity (for CoMFA: q2 = 0.51, r2 = 0.95, and for CoMSIA: q2 = 0.51, r2 = 0.93 and ). In summary, negative groups and steric bulk at ring “Y” and small groups at carbon-3 of ring “X” might be helpful in reducing
the mutagenicity of azo dyes. 相似文献
11.
Fluctuating hydrochemistry, as a result of extreme hydrological regimes, imposes major physiological constraints on the biota
of ephemeral saline lakes. While the inverse relationship between salinity and zooplankton species richness is well-known
across salinity gradients, few studies have documented closely the response of zooplankton to seasonal changes in salinity.
Weekly sampling during two flood seasons at Sua Pan, an intermittent saline lake in central Botswana demonstrated the importance
of spatial and temporal salinity gradients for crustacean community composition, associated with a decline in species richness,
from 11 to three species. Conductivity ranged between 320 and 125,800 μS cm−1 during seasonal flooding; changing from dominance by
and , Ca2+ and Mg2+, at the beginning of the floods, to NaCl dominated waters as the lake dried out and salinities increased. pH estimates generally
ranged between 8.6 and 10, with maximum values recorded during initial flooding. Crustaceans comprised mainly Branchinella spinosa, Moina belli, Lovenula africana and Limnocythere tudoranceai, all of which occurred across a wide range of salinities, while halotolerant freshwater species (Metadiaptomus transvaalensis, Leptestheria striatochonca and the ostracods Plesiocypridopsis aldabrae, Cypridopsis newtoni and a newly identified Potamocypris species) disappeared above conductivities of 1,500 μS cm−1. A unique crustacean composition in southern Africa was attributed to Sua Pans’ rare chemical composition among southern
African saline lakes; flood waters on Sua Pan contained a higher proportion of Na+ and , and less K+, Mg2+ and than over 80% of records from salt pans elsewhere in southern African. The freshwater species of crustaceans in Sua Pan were
similar to those found in other southern Africa lakes, and these similarities decreased in lakes with higher pH and proportions
of Na, and less SO4 and Mg in their chemical composition. The predominant saline tolerant species on Sua Pan, however, showed a greater similarity
to those in saline lakes in southern and East Africa with higher proportions of and, particularly, Mg2+ in their chemical composition.
Handling editor: J. M. Melack 相似文献
12.
A steady supply of water is indispensable for leaves to fulfil their photosynthetic function. Understanding water movement
in leaves, especially factors that regulate the movement of water flux from xylem to epidermis, requires that the nature of
the transport pathway be elucidated. To determine the hydraulic linkage between xylem and epidermis, epidermal cell turgor
pressure (P
t) in leaves of Tradescantia fluminensis was monitored using a cell pressure probe in response to a 0.2 MPa step change in xylem pressure applied at the leaf petiole.
Halftime of P
t changes
were 10–30 times greater than that of water exchange across an individual cell membrane suggesting that cell-to-cell water transport constitutes a significant part of the leaf hydraulic path from xylem to epidermis.
Furthermore, perfusion of H2O2 resulted in increases of both and by a factor of 2.5, indicating that aquaporins may play a role in the xylem to epidermis hydraulic link. The halftime for
water exchange did not differ significantly between cells located at the leaf base (2.5 s), middle (2.6 s) and tip (2.5 s), indicating that
epidermal cell hydraulic properties are similar along the length of the leaf. Following the pressure application to the xylem
(0.2 MPa), P
t changed by 0.12, 0.06 and 0.04 MPa for epidermal cells at the base, middle and the tip of the leaf, respectively. This suggests
that pressure dissipation between xylem and epidermis is significant, and that the pressure drop along the vein may be due
to its structural similarities to a porous pipe, an idea which was further supported by measurements of xylem hydraulic resistance
using a perfusion technique. 相似文献
13.
Leaching losses of inorganic N and DOC following repeated drying and wetting of a spruce forest soil
Forest soils are frequently subjected to dry–wet cycles, but little is known about the effects of repeated drying and wetting
and wetting intensity on fluxes of , and DOC. Here, undisturbed soil columns consisting of organic horizons (O columns) and organic horizons plus mineral soil
(O + M columns) from a mature Norway spruce stand at the Fichtelgebirge; Germany, were repeatedly desiccated and subsequently
wetted by applying different amounts of water (8, 20 and 50 mm day−1) during the initial wetting phase. The constantly moist controls were not desiccated and received 4 mm day−1 during the entire wetting periods. Cumulative inorganic N fluxes of the control were 12.4 g N m−2 (O columns) and 11.4 g N m−2 (O + M columns) over 225 days. Repeated drying and wetting reduced cumulative and fluxes of the O columns by 47–60 and 76–85%, respectively. Increasing (0.6–1.1 g N m−2) and decreasing fluxes (7.6–9.6 g N m−2) indicate a reduction in net nitrification in the O + M columns. The negative effect of dry–wet cycles was attributed to
reduced net N mineralisation during both the desiccation and wetting periods. The soils subjected to dry–wet cycles were considerably
drier at the final wetting period, suggesting that hydrophobicity of soil organic matter may persist for weeks or even months.
Based on results from this study and from the literature we hypothesise that N mineralisation is mostly constrained by hydrophobicity
in spruce forests during the growing season. Wetting intensity did mostly not alter N and DOC concentrations and fluxes. Mean
DOC concentrations increased by the treatment from 45 mg l−1 to 61–77 mg l−1 in the O tlsbba columns and from 12 mg l−1 to 21–25 mg l−1 in the O + M columns. Spectroscopic properties of DOC from the O columns markedly differed within each wetting period, pointing
to enhanced release of rather easily decomposable substrates in the initial wetting phases and the release of more hardly
decomposable substrates in the final wetting phases. Our results suggest a small additional DOC input from organic horizons
to the mineral soil owing to drying and wetting. 相似文献
14.
A carbon membrane-aerated biofilm reactor (CMABR) was developed to treat synthetic wastewater. Such membrane exhibited a high
degree of adhesion and good permeability. Continuous experiments showed that COD and
-N removal efficiency were 90 ± 2 and 92 ± 4% at removal rates of 35.6 ± 3.8 g COD/m2 per day and 9.3 ± 0.6 g
-N/m2 per day, respectively. After 108 days, effluent total nitrogen (TN) kept at 35 ± 4 mg/L when influent
-N increased to 144–164 mg/L and removal efficiency of TN reached 78 ± 3%. Furthermore, Stoichiometric analysis revealed that
70–90% of oxygen supplied was consumed by nitrifier. Scanning electron microscopic (SEM) images and component analysis of
penetrating fluid revealed that extracellular polymeric substance (EPS) adhered to pore and that alkaline washing was an effective
method to remove them. The study demonstrated that carbon membrane could be used as effective gas-permeable membrane in MABR
for wastewater treatment. 相似文献
15.
Jean-Philippe Bellenger Françoise Arnaud-Neu Zouhair Asfari Satish C. B. Myneni Edward I. Stiefel Anne M. L. Kraepiel 《Journal of biological inorganic chemistry》2007,12(3):367-376
Azotochelin is a biscatecholate siderophore produced by the nitrogen-fixing soil bacterium Azotobacter vinelandii. The complexation properties of azotochelin with a series of oxoanions [Mo(VI), W(VI) and V(V)] and divalent cations [Cu(II),
Zn(II), Co(II) and Mn(II)] were investigated by potentiometry, UV–vis and X-ray spectroscopy. Azotochelin forms a strong 1:1
complex with molybdate (log K = 7.6 ± 0.4) and with tungstate and vanadate; the stability of the complexes increases in the order Mo < V < W (log K
appMo = 7.3 ± 0.4; log K
appV = 8.8 ± 0.4 and log K
appW = 9.0 ± 0.4 at pH 6.6). The Mo atom in the 1:1 Mo–azotochelin complex is bound to two oxo groups in a cis position and to the two catecholate groups of azotochelin, resulting in a slightly distorted octahedral configuration. Below
pH 5, azotochelin appears to form polynuclear complexes with Mo in addition to the 1:1 complex. Azotochelin also forms strong
complexes with divalent metals. Of the metals studied, Cu(II) binds most strongly to azotochelin , followed by Zn(II) , Mn(II) and Co(II) . Since very few organic ligands are known to bind strongly to oxoanions (and particularly molybdate) at circumneutral pH,
the unusual properties of azotochelin may be used for the separation and concentration of oxoanions in the laboratory and
in the field. In addition, azotochelin may prove useful for the investigation of the biogeochemistry of Mo, W and V in aquatic
and terrestrial systems.
Electronic supplementary material Supplementary material is available in the online version of this article at and is accessible for authorized users. 相似文献
16.
Solvated electrons () are produced during water radiolysis and can interact with biological substrates, including DNA. To augment DNA damage,
radiosensitizers such as bromo-deoxyuridine (BUdR), often referred to as an “electron affinic radiosensitizer”, are incorporated
in place of isosteric thymidine. However, little is known about the primary interactions of with DNA. In the present study we addressed this problem by applying molecular modeling and molecular dynamics (MD) simulations
to a system of normal (BUdR·A)-DNA and a hydrated electron, where the excess electron was modeled as a localized (H2O)6 anionic cluster. Our goals were to evaluate the suitability of the MD simulations for this application; to characterize the
motion of around DNA (e.g., diffusion coefficients); to identify and describe configurational states of close localization to DNA; and to evaluate the structural dynamics of DNA in the presence of . The results indicate that has distinct space-preferences for forming close contacts with DNA and is more likely to interact directly with nucleotides
other than BUdR. Several classes of DNA - contact sites, all within the major groove, were distinguished depending on the structure of the intermediate water layer
H-bonding pattern (or its absence, i.e., a direct H-bonding of with DNA bases). Large-scale structural perturbations were identified during and after the approached the DNA from the major groove side, coupled with deeper penetration of sodium counterions in the minor groove.
Figure A rare configuration showing direct interaction between the solvated electron and DNA, where (yellow) and N7(A16) are H-bonded. The close approach from the major groove side invokes deep Na+ (magenta) penetration into the minor DNA groove (Fig. 7a). 相似文献
17.
A mechanical molecular rotation model for liquid crystal (LC) systems is employed to evaluate phase transition temperature
of fluorinated phenylbicyclohexane isomeric LC compounds. Results show that when a fluorine atom is substituted along the
molecular long axis, an LC molecule acquires high rotational speed and its rotation becomes stable, thereby resulting in a
better thermal stability of the nematic phase. A novel explanation is proposed for the behavior of the nematic-isotropic phase
of the LC system when a heavy atom is substituted along the molecular long axis.
Figure Molecular conformation of fluorinated bicyclohexylphenyl compounds. . The fluorine atoms are substituted in different positions 2, 3, 4, and 5 of the phenyl ring, respectively. The axis expresses
molecular long rotation axis. 相似文献
18.
A 3D QSAR analysis has been performed on a series of 67 benzodiazepine analogues reported as γ-secretase inhibitors using
molecular field analysis (MFA), with G/PLS to predict steric and electrostatic molecular field interaction for the activity.
The MFA study was carried out using a training set of 54 compounds. The predictive ability of model developed was assessed
using a test set of 13 compounds ( as high as 0.729). The analyzed MFA model has demonstrated a good fit, having r2 value of 0.858 and cross validated coefficient, value as 0.790. The analysis of the best MFA model provided insight into possible modification of the molecules for better
activity.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
19.
Xingliang Xu Claus Florian Stange Andreas Richter Wolfgang Wanek Yakov Kuzyakov 《Plant and Soil》2008,304(1-2):59-72
Effects of light on the short term competition for organic and inorganic nitrogen between maize and rhizosphere microorganisms
were investigated using a mixture of amino acid, ammonium and nitrate under controlled conditions. The amount and forms of
N added in the three treatments was identical, but only one of the three N forms was labeled with 15N. Glycine was additionally labeled with 14C to prove its uptake by maize and incorporation into microbial biomass in an intact form. Maize out-competed microorganisms
for during the whole experiment under low and high light intensity. Microbial uptake of 15N and 14C was not directly influenced by the light intensity, but was indirectly related to the impact the light intensity had on
the plant. More was recovered in microbial biomass than in plants in the initial 4 h under the two light intensities, although more 15N-glycine was incorporated into microbial biomass than in plants in the initial 4 h under low light intensity. Light had a
significant effect on uptake by maize, but no significant effects on the uptake of or 15N-glycine. High light intensity significantly increased plant uptake of and glycine 14C. Based on 14C to 15N recovery ratios of plants, intact glycine contributed at least 13% to glycine-derived nitrogen 4 h after tracer additions,
but it contributed only 0.5% to total nitrogen uptake. These findings suggest that light intensity alters the competitive
relationship between maize roots and rhizosphere microorganisms and that C4 cereals such as maize are able to access small
amounts of intact glycine. We conclude that roots were stronger competitor than microorganisms for inorganic N, but microorganisms
out competed plants during a short period for organic N, which was mineralized into inorganic N within a few hours of application
to the soil and was thereafter available for root uptake. 相似文献
20.
Wu X Xiao W Liu C Chao L Qu C Chunxiang Q Huang H Hao H Liu X Xiaoqing L Chen L Liang C Su M Mingyu S Hong F Fashui H 《Biological trace element research》2008,121(3):258-265
Lead (Pb2+) is a well-known highly toxic element. The mechanisms of the Pb2+ toxicity are not well understood for nitrogen metabolism of higher plants. In this paper, we studied the effects of various
concentrations of PbCl2 on the nitrogen metabolism of growing spinach. The experimental results showed that Pb2+ treatments significantly decreased the nitrate nitrogen absorption and inhibited the activities of nitrate reductase, glutamate dehydrogenase, glutamine synthase, and glutamic–pyruvic
transaminase of spinach, and inhibited the synthesis of organic nitrogen compounds such as protein and chlorophyll. However,
Pb2+ treatments increased the accumulation of ammonium nitrogen in spinach cell. It implied that Pb2+ could inhibit inorganic nitrogen to be translated into organic nitrogen in spinach, thus led to the reduction in spinach
growth. 相似文献