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1.
The influences of fulvic acid (FA) on bioavailability and toxicity of selenite for wheat seedling and growth were studied
by green-house hydroponic experiment. The results showed that seed germination, embryo development, and growth were stimulated
by selenite in the concentration range of 0.1–1.0 mg/L. In the presence of FA, the stimulation effects were more obviously
observed. However, when the concentration of selenite exceeded 1.0 mg/L, toxic effects were observed for most of the measured
indicators. The presence of FA could reduce the bioavailability of Se and could antagonize the toxic effects of Se. The reasons
for the antagonism were caused by the inhibitory effects of FA on uptake of Se by plants and by the stimulating effects of
FA on plant growth. 相似文献
2.
The wheat in hydroponics culture has been chosen as a model to study the dose-effect relationship of selenite with its growth. Five different morphological end points and 12 different biological and biochemical end points during different phases of growth of wheat seedling and seed germination have been measured and analyzed. A dose-effect relationship of selenite with the growth of wheat has been obtained from data analysis. The results shows that critical threshold for beneficial effect is about 1.0 mg Se/L, and the critical threshold for adverse effect is about 5.0 mg Se/L in hydroponics culture. From the result of product of lipid peroxidation, it is assumed that the role of selenium for plant is related to the oxy-radical reaction. 相似文献
3.
Selenium (Se) is an essential trace element for humans and animals. A hydroponic experiment was performed to study the effects of sulphur (S) on Se uptake, translocation, and assimilation in wheat (Triticum aestivum L.) seedlings. Sulphur starvation had a positive effect on selenate uptake and the form of Se supplied greatly influenced Se speciation in plants. Compared with the control plants, Se uptake by the S-starved plants was enhanced by 4.81-fold in the selenate treatment, and selenate was readily transported from roots to shoots. By contrast, S starvation had no significant effect on selenite uptake, and selenite taken up by roots was rapidly converted to organic forms and tended to accumulate in roots. X-ray absorption near edge spectroscopy (XANES) analysis showed that organic forms of selenium, including selenocystine, Se-methyl-selenocysteine (MeSeCys), and selenomethionine-Se-oxide, were dominant in the plants exposed to selenite and accounted for approximately 90 % of the total Se. Whereas selenate remained as the dominant species in the roots and shoots exposed to selenate, with little selenate converted to selenite and MeSeCys. Besides, sulphur starvation increased the proportion of inorganic Se species in the selenate-supplied plants, but had no significant effects on Se speciation in plants exposed to selenite. The present study provides important knowledge to understand the associated mechanism of Se uptake and metabolism in plants. 相似文献
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Regula Würmli Siegfried Wolffram Yvonne Stingelin Erwin Scharrer 《Biological trace element research》1989,20(1-2):75-85
The influence of cysteine (Cys) on mucosal uptake of 75Se-labeled selenite in sheep midjejunum was investigated using a short-term uptake technique. L-Cys (concn.: 1.0 mmol/L) significantly stimulated uptake of Se from selenite (concn.: 10 mumols/L). The stimulatory effect of L-Cys on mucosal uptake of Se from selenite was Na(+)- and pH-dependent. In the absence of Na+, or at an acidic pH (5.0), the stimulatory effect of L-Cys was abolished. L-alanine and L-lysine, but not L-glutamic acid inhibited uptake of Se from selenite in the presence of L-Cys. Preincubation of mucosal preparations with 10 mmol/L L-Cys produced enhanced mucosal uptake of Se from selenite. It is concluded from these results that L-Cys stimulates absorption of Se from selenite probably by generation of selenodicysteine and maybe cysteine selenopersulfide that are subsequently transported across the intestinal brush border membrane by Na(+)-dependent amino acid carriers. Furthermore, intracellular generation of selenodicysteine might contribute to the uptake of Se from selenite by maintaining the concentration gradient for diffusive uptake of selenite. 相似文献
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8.
The effects of selenium (Se) on ruminant microbial fermentation were investigated in vitro using rumen microflora collected
from a rumen-fistulated dairy cow. First, the effects ofl-selenomethionine (SeMet; at 0.2 or 2 ppm Se) in the presence or absence of wheat bran (WB, 500 mg per incubation flask) were
evaluated. Second, the effects of several forms of Se (elemental Se: 50 ppm Se; sodium selenite: 2 ppm Se; SeMet: 2 ppm Se)
were compared. Results showed that the amounts of short-chain fatty acids (SCFAs) tended to be increased by SeMet treatment,
whereas SeMet in the presence of WB transiently suppressed fermentation. The addition of SeMet tended to increase the production
of acetate while reducing the production of butyrate with and without WB supplementation. Among the different Se compounds
tested, the amounts of SCFAs were greater with SeMet treatment, which yielded a higher proportion of acetate compared to other
treatments. Selenite did not influence the total SCFAs concentrations; however, it increased the relative proportion of butyrate
at the expense of acetate. Elemental Se did not significantly affect fermentation. Higher bacterial Se concentrations were
observed for selenite than for SeMet. It was concluded that Se supplementation can influence rumen microbial fermentation
and that Se compounds differ in this regard. 相似文献
9.
The stability constants of complexes formed between iron (III) and fulvic acid extracted from organic manures and wastes such
as urban domestic sewage sludge, farmyard manure, poultry manure and sulfitation pressmud were investigated by the potentiometric
titration method in an ionic medium of 0.1 M KNO3 at 25±1 °C. A modification of the Katchalsky's model was employed for the estimation of stability constants. The displacement
of the titration curves due to presence of Fe3+ in FA solutions formed the basis of calculations. The weak acidic property of fulvic acids due to carboxyl groups resulted
in buffering over a wide range of pH; fulvic acids were completely neutralized in the pH range of 7.00–8.85. Apparent dissociation
constants (pKAPP) of weakly acidic carboxyl groups were a direct function of degree of dissociation (αL) in the mid-range of titration curves but were non-linear at high and low αL values. The stability constants for formation of Fe–FA complexes (log βFe) calculated from the titration data were in the range of 5.64–7.55, depending upon αL and electrostatic properties of fulvic acids. The relatively high stability constants of Fe–FA complexes in comparison to
those with other competing cations suggest that the Fe–FA complexes are relatively stable in a soil environment.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
10.
Halina M. Zbikowska Barbara Wachowicz Tadeusz Krajewski 《Biological trace element research》1997,57(3):259-269
The effects of inorganic selenium (Se) compounds (sodium selenite and selenate) on the activities of glutathione-related enzymes
(glutathione peroxidase, glutathione-S-transferase [GST] and glutathione reductase [GR]) in pig blood platelets were investigated
in vitro. GST activity in blood platelets treated with 10−4
M of selenite was reduced to 50%, whereas no decrease GST activity was observed after the treatment of platelets with the same
dose of selenate. In platelets incubated with physiological doses (10−7, and 10−6
M) of Se compounds, the activity of glutathione peroxidase (GSH-Px) was enhanced (about 20%). GR activity after the exposure
of platelets to tested Se compounds was unaffected. 相似文献
11.
New experimental observation on the relationship of selenium and diabetes mellitus 总被引:12,自引:0,他引:12
Selenium shows insulin-mimic properties in vitro and in vivo. However, in this study, a high dose of 4 mg/kg/d selenite orally
administered to the alloxan-induced diabetic Kun-Ming mice for 4 wk failed to reduce hyperglycemia. Se contents in plasma
and tissues such as the liver, kidney, spleen, and brain were determined and the thiobarbituric acid-reactive substances (TBARS)
levels were investigated. The results showed that alloxan-induced diabetes did not cause a significant decrease in Se levels
in plasma and the above tissues compared to the normal control, but selenite treatment significantly increased Se levels in
plasma, liver, and brain of the selenite-treated diabetic mice compared to the nontreated diabetic mice. In addition, selenite
treatment for diabetic mice reduced the TBARS levels in red blood cells (RBCs) compared to the normal and improved the glutathione
peroxidase (GSH-Px) levels in RBCs significantly compared to the diabetic control. In conclusion, this study demonstrated
that although oral administration of a high dose of selenite had no hypoglycemic effect on diabetic mice in 4 wk, selenite
treatment still maintained the antioxidant beneficial effect on the diabetic mice. This study shed more light on the relationship
between Se and diabetes. 相似文献
12.
Thirunavukkarasu C Premkumar K Jagadeeswaran R Sakthisekaran D 《Molecular and cellular biochemistry》2005,280(1-2):165-172
In the present study, we have evaluated the effects of dietary selenite (Se) on polyamine levels and its influence on N-nitrosodiethylamine (DEN) initiated and Phenobarbital (PB) promoted in rat liver carcinogenesis. Dietary selenite at a concentration
of 4 ppm (through drinking water) was administered in rats either before initiation (4 weeks), or during promotion (16 weeks)
and entire experimental period (20 weeks). Male Wistar strain of albino rats was treated with single intra peritoneal dose
of DEN (200 mg kg−1 body weight), after 2 weeks the carcinogenic effect was promoted by PB (0.05%; through diet). Alpha fetoprotein (AFP) was
investigated after the 20th-week of experimental period. Selenite-treated animals markedly reduced the AFP during the time
of pre-selenite [before initiation (4 weeks)] and entire experimental period (20 weeks), administration rather than the promotion
period. This infers that anticancer property of selenite depends on the stage of carcinogenesis, rather than duration of treatment.
Evaluation of polyamine levels in hepatoma and surrounding liver tissue showed significant difference in the selenite-treated
groups compared with pair-fed control groups. Furthermore, histopathological examination showing remarkable difference between
control and treated groups. These results demonstrate that selenite can modulate the development of DEN-induced and PB-promoted
rat liver carcinogenesis through a polyamine-dependent mechanism. (Mol Cell Biochem xxx: 165–172, 2005) 相似文献
13.
Esther Senn Erwin Scharrer Siegfried Wolffram 《Biological trace element research》1992,33(1-3):103-108
The influence of glutathione (1 mmol/L) (GSH) on in vitro mucosal uptake and in vivo absorption of75Se-labeled selenite (10 μmol/L) was investigated in rat jejunum. For comparison, the effect ofl-cysteine (1 mmol/L) on in vivo absorption of75Se-labeled selenite was also studied. In the in vitro, uptake experiments, only the mucosal surface was exposed to the incubation
medium for 3 min. For the in vivo experiments, a luminal perfusion technique was employed. GSH inhibited in vitro mucosal
Se uptake, whereas absorption in vivo was stimulated by GSH.l-Cysteine also stimulated in vivo Se absorption, confirming former in vitro mucosal uptake experiments. Thus, unlikel-cysteine, GSH affected in vitro and in vivo absorption of Se from selenite differently. Enzymatic cleavage of products of
the reaction of selenite with GSH occuring more efficiently under in vivo than in vitro conditions may be a prerequisite for
the stimulatory effect of GSH on Se absorption. This apparently does not apply to the stimulatory effect of cysteine. Since,
GSH occurs in the intestinal lumen under physiological conditions, it may contribute to the high bioavailability of Se from
selenite. 相似文献
14.
黄腐酸和甜菜碱预处理对干旱胁迫下平邑甜茶生理特性及光合的影响 总被引:1,自引:0,他引:1
该研究以平邑甜茶[Malus hupehensis(Pamp.)Rehd.]2年生实生苗为材料,通过盆栽试验于干旱处理前3d分别连续喷施黄腐酸(FA)、甜菜碱(GB)和复配(FA+GB),并以清水为对照(CK)进行预处理,比较分析不同预处理对干旱胁迫下平邑甜茶的生理及光合特性变化,探讨FA和GB对平邑甜茶的抗旱生理机制。结果显示:(1)与对照相比,FA、GB和FA+GB预处理均能够显著提高平邑甜茶叶片相对含水量,且FA的保水性效果最佳。(2)3种预处理均可显著促进干旱胁迫下叶片可溶性蛋白、可溶性糖和脯氨酸含量增加,且FA+GB预处理后在干旱胁迫下叶片可溶性糖和脯氨酸累积量显著高于单施FA或GB。(3)3种预处理均可显著提高干旱胁迫下平邑甜茶幼苗的SOD、POD、CAT活性,并显著降低MDA的积累速度及其累积量,且以FA+GB预处理的MDA含量最低、抗氧化酶活性最高。(4)GB和FA+GB预处理下平邑甜茶的净光合速率、瞬时水分利用率显著高于CK和FA,且FA+GB处理下改善光合特性的效果最佳,GB次之。研究表明,单独喷施黄腐酸和甜菜碱及两者配施预处理均能够增加干旱胁迫下平邑甜茶的渗透调节物质和相对含水量,提高叶片的保水性,调节抗氧化物酶活性,降低丙二醛含量,增加细胞膜稳定性,改善光合性能,进而提高平邑甜茶的抗旱能力,且以复配喷施(FA+GB)预处理的效果最好。 相似文献
15.
S. P. Makarenko L. V. Dudareva A. I. Katyshev T. A. Konenkina A. V. Nazarova E. G. Rudikovskaya N. A. Sokolova V. V. Chernikova Yu. M. Konstantinov 《Biochemistry (Moscow) Supplemental Series A: Membrane and Cell Biology》2011,5(1):64-69
The study was focused on fatty acid (FA) composition of lipids from the seedlings and roots of crops having different cold
resistance and grown at 27°C or 4°C. Biosynthesis of FA in the lipids of seedlings and roots of cold-susceptible maize (Zea mays L.) at both growth temperatures was controlled by chloroplast ω6 desaturase and microsomal ω6 desaturase, respectively. The
content of linoleic acid was 56.2% and 43.3% in the coleoptiles of maize seedlings grown at 4 and 27°C, respectively, and
in the roots it was 52.2% and 38.5%, respectively. The content of α-linolenoic acid in the coleoptiles was 6.7–6.8% at both
temperatures, while in the root lipids it was higher at low temperature (3.15% at 27°C vs. 4.7% at 4°C). FA biosynthesis in
the seedling coleoptiles of wheat (Triticum aestivum L.) and Siberian wild rye (Elymus sibiricus L.) grown at low temperature was controlled by the chloroplast ω3 desaturase. A minor increase in the content of α-linolenoic
acid was observed at low temperature: 29.7% to 30.2% in wheat and 22.8% to 25.8% in wild rye. In the root tissues of these
species, the biosynthesis of α-linolenoic acid was controlled by the microsomal ω3 desaturase. The content of α-linolenoic
acid was higher at low temperature: in wheat it was 6.1% at 27°C and 17.1%, and 4°C, while in Siberian wild rye, 7.1% and
12.0% at 4 and 27°C, respectively. 相似文献
16.
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The forms of Se in the Se-dependent enzyme formate dehydrogenase is known to be selenocysteine, but the way this amino acid enters the polypeptide chain has not been established. Through the use of a cysteine-requiring mutant ofEscherichia coli K-12 that could also grow in the presence of glutathione, we were able to study the effect of selenite, selenide, andl-selenocysteine, each at a concentration of 0.1 μM, on the synthesis of formate dehydrogenase. The three forms of Se served equally well for inducing formate dehydrogenase activity, measured by dichlorophenol-indophenol reduction mediated by phenazine methosulfate. It is known that selenite can be reduced to selenide by the action of glutathione reductase, present inE. coli, and that selenocysteine is converted to elemental Se by the action of selenocysteine lyase, also present in the mutant. Elemental Se is then reduced nonenzymatically to hydrogen selenide. The conversion of both selenite and selenocysteine to selenide and the ability of each form of Se to induce the synthesis of equal levels of formate dehydrogenase suggest that the incorporation of Se into formate dehydrogenase is accomplished by a posttranslational mechanism. 相似文献
18.
Uptake of Selenium and its Antioxidant Activity in Ryegrass When Applied as Selenate and Selenite Forms 总被引:10,自引:0,他引:10
Selenium (Se) is an essential micronutrient for animal and human nutrition, but whether it is essential to plants remains
controversial. However, there are increasing experimental evidences that indicate a protective role of Se against the oxidative
stress in higher plants through Se-dependent glutathione peroxidase (GSH-Px) activity. The effects of the Se chemical forms,
selenite and selenate, the rate of their application on shoot Se concentration and their influence on the antioxidative system
of ryegrass (Lolium perenne cv. Aries), through the measurement of GSH-Px activity and lipid peroxidation, were evaluated in an Andisol of Southern Chile.
Moreover, a soil–plant relationship for Se was determined and a simple method to extract available Se from acid soils is proposed.
In a 55-day experiment ryegrass seeds were sown in pots and soil was treated with sodium selenite or sodium selenate (0–10
mg Se kg−1). The results showed that the Se concentration in shoots increased with the application of both selenite and selenate. However,
the highest shoot Se concentrations were obtained in selenate-treated plants. For both sources of Se, there was a significant
positive correlation between the shoot Se concentration and the GSH-Px activity; and the Se-dependence of this enzymatic activity
was related especially with the chemical form of applied Se rather than the Se concentration in plant tissues. Furthermore,
the lipid peroxidation, as measured by Thiobarbituric Acid Reactive Substances (TBARS), decreased at low levels of shoot Se
concentration, reaching the lowest level at approximately 20 mg Se kg−1 in plants and then increased steadily above this level. In addition, the acid extraction method used to evaluate available
Se in soil showed a positive good correlation between soil Se and shoot Se concentrations irrespective of chemical form of
Se applied. 相似文献
19.
The effect of fulvic acids (FA) on arbuscular mycorrhizal (AM) fungi and on the toxicity of lead and manganese toward these
symbionts were demonstatedin vitro. Incubation of root segments colonized with the AM fungusGlomus intraradices in undiluted fraction of FA (813 mg/L carbon) decreased an outgrowth of intraradical hyphae. Diluted FA solutions (<271 mg/L
C) did not influence the proportion of root segments bearing proliferating hyphae; solution containing 27.1 mg/L C even increased
the proliferation. A decrease of heavy metal toxicity toward the fungus was observed when FA (81.3 mg/L C) were added to the
solutions containing higher concentrations (≤100 μmol/L) of Mn and Pb; the positive effect of FA was not significant at higher
concentrations of metals (0.5 mmol/L). A short-term cultivation of six different saprophytic microorganisms — three actinomycetes
and three filamentous fungi — on the FA media (81.3 mg/L C) did not result in a modification of hyphal proliferation from
the root segments subsequently incubated in these media. 相似文献
20.
The effect of topography on the nature of humic substances, isolated as water soluble organic carbon (WSOC), fulvic acid (FA), and humic acid (HA) was evaluated by comparing relative proportion and chemical characteristics of these fractions in upland and bottomland Coastal Plain soils in South Carolina. The fractions were characterized by elemental analysis and13C cross-polarization magic angle spinning nuclear magnetic resonance (CPMAS NMR) spectroscopy. The majority of humic substances occur as humic acids, with bottomland soils having higher HA/FA ratios when compared to upland soils. We found no significant differences between upland and bottomland humic substances with respect to yields of WSOC and fulvic acids, and in the C and N content of humic and fulvic acids. Carbon-13 CPMAS NMR spectroscopy revealed that the WSOC and fulvic acid fractions were composed largely of O-alkyl-C structures with bottomland soils having higher amounts of these groups. Humic acid C distribution was similar between upland and bottomland soils and was largely composed of aromatic groups. Our results demonstrate that topography influences the formation of humic acid and the structural and chemical properties of the various humic fractions.requests for offprints 相似文献