Influence of some metal chelators and light regimes on bioaccumulation and toxicity of Cd2+ in duckweed (Lemna gibba)

A factorial culture experiment was designed to investigate the influence of light regimes and of some metal chelators on the accumulation of cadmium by Lemna gibba L. The plants were grown in a complete nutrient solution containing Cd²⁺ concentrations ranging from 0 to 27 μ M with or without EDTA, ethylenediamine-N,N'- bis -( o -hydroxyphenylacetic acid) (EDDHA) or salicylic acid. Each experiment was run for eight days in 18 h:6 h light:dark or continuous light. An increase in the Cd²⁺ concentration in plants and a simultaneous drop in accumulation efficiency (ratio of Cd²⁺ concentration in plants to the initial Cd²⁺ concentration in the nutrient solution) with increasing ambient Cd²⁺ levels was best represented by regression power curves. At the lowest Cd²⁺ concentration which caused a significant decrease in the relative growth rate of duckweed, there was a decrease in manganese and zinc and an increase in the iron level in the plants. EDDHA and EDTA protected in some cases against the toxic action of cadmium without preventing its uptake by plants. It was thus observed that 9 μ M or higher levels of Cd²⁺ were toxic to Lemna gibba depending on the chelator and light regime. Duckweed grown in continuous light produced, in general, more dry matter and hence accumulated more cadmium.     

Mobilization of ferritin iron in erythroblasts by chelating agents

Intracellular ferritin in newt (Triturus cristatus) erythroblasts was accessible to the chelating effects of EDTA and pyridoxal phosphate. EDTA (0.5-1 mM) promoted release of radioactive iron from ferritin of pulse-labelled erythroblasts during chase incubation, but its continuous presence was not necessary for ferritin iron mobilization. Brief exposure to EDTA was sufficient to release 60-70% of ferritin 59Fe content during ensuing chase in EDTA-free medium. EDTA also suppressed cellular iron uptake and utilization for heme synthesis, but these activities were restored upon its removal. Pyridoxal-5'-phosphate (0.5-5 mM) also stimulated loss of radioactive iron from ferritin; however, ferritin iron release by pyridoxal phosphate required its continued presence. Unlike EDTA, pyridoxal phosphate did not interfere with iron uptake or its utilization for heme synthesis. Chelator-mobilized ferritin iron accumulated initially in the hemolysate as a low-molecular-weight component and appeared to be eventually released into the medium. No radioactive ferritin was found in the medium of chelator-treated cells, indicating that secretion or loss of ferritin was not responsible for decreasing cellular ferritin 59Fe content. Moreover, there was no transfer of radioactive iron between the low-molecular-weight component released into the medium and plasma transferrin. These results indicate that chelator-released ferritin iron is not available for cellular utilization in heme synthesis and that ferritin iron released by this process is not an alternative or complementary iron source for heme synthesis. Correlation of these data with effects of succinylacetone inhibition of heme synthesis and with previous studies indicates that the main role of erythroid cell ferritin is absorption and storage of excess iron not used for heme synthesis.     

水杨酸对马铃薯试管微薯形成的影响研究

研究了不同浓度水杨酸（ＳＡ）对马铃薯脱毒试管苗生长,分化及试管微薯诱导和发育的 浓度ＳＡ显著抑帛式管苗主茎和根的生长,促进侧枝和匍匐茎分化。高浓度（０．１－１．０ｍｍｏｌ／Ｌ）ＳＡ能诱导试管微薯形成并显著提高结薯率。ＳＡ浓度为０．５ｍｍｏｌ／Ｌ时,结薯率最高,且成薯集中,薯块大小整齐一致。     

Release of iron from transferrin by phosphonocarboxylate and diphosphonate chelating agents

The rates at which phosphonocarboxylate and diphosphonate ligands remove iron from the serum iron transport protein transferrin at 25 degrees C and pH 7.4 have been evaluated. These ligands show a combination of saturation and first-order kinetics with respect to the free ligand concentrations. The ability of the ligands to remove iron from transferrin appears to be subject to steric restrictions that are essentially identical to those associated with the ability of a ligand to substitute for the synergistic carbonate anion. This observation supports the hypothesis that the first-order component for iron removal involves a mechanism in which the rate-limiting step is the slow substitution of the synergistic carbonate by the incoming chelating agent. Studies on monoferric transferrins indicate that phosphonocarboxylates are unusually effective at removing iron from the C-terminal site of the protein. Difference UV spectroscopy has been used to show that the phosphonocarboxylates bind strongly to apotransferrin. It is suggested that the rapid release of iron from the C-terminal site may be due to the binding of the ligand to an allosteric anion-binding site in the C-terminal lobe of the protein.     

Fe-EDDHA对矫治秦美猕猴桃叶片失绿和营养元素组成的影响

在陕西石灰性土壤秦美猕猴桃果园施用不同剂量叶绿灵 (Fe- EDDHA) ,结果表明 ,萌芽期株施 45 g叶绿灵对矫治秦美猕猴桃叶片失绿黄化效果显著 ,可一直维持到当年落叶。同黄化对照植株相比 ,叶片叶绿素含量增加 1 82 .5 % ,活性铁含量提高 5 3 .2 % ,果实品质得到明显改善。施用叶绿灵还改善了叶片营养元素的含量     

A comparative study of the effects of natural and synthetic ligands on iron uptake by plants

Summary The uptake of iron by wheat seedlings was investigated using half-strength Hoagland's nutrient solution containing 2.0 M ferric chloride labelled with⁵⁹Fe. The iron content of root tissue, which includes adsorbed iron, was depressed by the presence in the solution of the synthetic ligands EDTA and polymaleic acid (PMA) and by the natural ligands, humate, fulvate and a water-extractable soil polycarboxylate. The patterns of change in iron content of the shoots were in all cases different from those of the roots and were of two types. EDTA and humate increased the iron content of the shoots to maximum values, at ligand concentrations of 5.0 M and 2.5 mg l^–1 respectively, and decreased it at higher concentrations. Fulvate, water-extractable soil polycarboxylate and PMA increased the iron content of the shoots up to the maximum ligand concentrations tested (25 mg l^–1). These results are discussed in the light of the likely solution chemistry of iron and the various ligands.     

Effect of chelating agents and metal ions on the degradation of DNA by bleomycin.

The degradation of DNA by bleomycin was studied in the absence and in the presence of added reducing agents, including 2-mercaptoethanol, dithiothreitol, reduced nicotinamide adenine dinucleotide phosphate, H2O2, and ascorbate, and in the presence of a superoxide anion generating system consisting of xanthine oxidase and hypoxanthine. In all cases, breakage of DNA was inhibited by low concentrations of chelators; where examined in detail, deferoxamine mesylate was considerably more potent than (ethylenedinitrilo)tetraacetic acid. Iron was found to be present in significant quantities in all reaction mixtures. Thus, the pattern of inhibition observed is attributed to the involvement of contaminating iron in the degradation of DNA by bleomycin. Cu(II), Zn(II), and Co(II) inhibit degradation of DNA by bleomycin and Fe(II) in the absence of added reducing agents. A model is proposed in which the degradation of DNA in these systems is dependent on the oxidation of an Fe(II)-bleomycin-DNA complex.     

Effect of redox and chelating agents on the properties of chloroplast ATPase

The effect of redox and chelating reagents on the ATPase and ATP-synthetase activity in chloroplast membranes as well as the ATPase activity of isolated CF1-coupling factor from chloroplasts has been studied. The Mg2+-ATPase in thylakoid membranes and isolated Ca2+-ATPase is stimulated by dithionite. In the presence of reduced glutathione the effect of dithionite is similar to those of prolonged illumination or heating. Dichlorophenolindophenol partially inhibits this activity as well as citrate, tenoyltrifluoroacetone and the excess fo ATP. Photophosphorylation in chloroplast lamellae is inhibited with dithionite. It is suggested that the membrane bound ATPase from chloroplasts may be in two structural states which differ in their enzymic activity and in the coupling to electron transfer in membrane. The transitions between these states can be induced by redox reagents.     

Effects of three chelating agents,EDTA, NTA,and TPP,on the concentration of elements in rat tissues

Ethylene diamine tetraacetic acid (EDTA), nitrilotriacetic acid (NTA), and tripolyphosphate (TPP) sodium salts were given orally to rats at the dose of 1 mmol/kg/d for 35 d. The concentrations of Na, K, Ca, Mg, P, S, Fe, Sr, Cu, and Zn were determined in blood, plasma, brain, heart, muscle, liver, kidney, duodenum, and bone of control rats and of the rats receiving EDTA, NTA, and TPP. The main effect induced by EDTA, NTA, and TPP was a decrease of the concentrations of several elements Ca, Mg, Fe, P in the duodenum. Otherwise, EDTA induced an increase of Zn in the kidney (+ 20%), NTA, an increase of Fe in liver (+ 29%), and particularly an increase of Zn in bone (+ 44%). TPP induced a slight decrease of Zn and Cu in liver. In conclusion, EDTA, NTA, and TPP taken orally at the dose of 1 mmol/kg/d for 35 d induced moderate changes of the concentrations of some elements in rat tissues, but without signs of toxicity.     

Inactivation of intracellular copper-zinc superoxide dismutase by copper chelating agents without glutathione depletion and methemoglobin formation

The copper chelator N,N'-diethyldithiocarbamate (DDC), is often used to inactivate intracellular copper-zinc superoxide dismutase in erythrocytes. However, in studies with red cells we found that the compound also reacted with oxyhemoglobin to produce oxygen radicals in addition to generating lipid peroxidation products, oxidized N,N'-diethyldithiocarbamate, methemoglobin, and sulfhemoglobin. Moreover, intracellular glutathione was depleted and vital cellular enzymes were susceptible to inactivation. We, and others, have confirmed these findings in nonerythrocytic cell lines. Thus, cells exposed to DDC are severely damaged before studies on the effects of added putative superoxide producing compounds can be performed with them. In this report, we have systematically investigated other copper chelators for their ability to inactivate intracellular copper-zinc superoxide dismutase without producing the deleterious effects mentioned above. Catechol, triethylenetetramine, and tetraethylenepentamine were found to be such agents when erythrocytes were dialyzed in the cold against dilute solutions of these chelators. In addition, with a myeloid leukemic cell line (HL-60), triethylenetetramine inhibited SOD without causing significant GSH oxidation. Examination of the affinity constants of chelators active against purified copper-zinc superoxide dismutase indicated that an affinity binding constant (log K1) between 12.6 and 13.8 was required for the chelator to successfully remove copper from the enzyme.     

Effect of prevention of iron chlorosis on the quality of sugarcane grown on vertisols

Results of a field experiment comprising various sources of sulphur and iron showed that band application of sulphur @ 500 kg/ha significantly increased the mean sugar content by 5.6%, recovery of sugar by 5.8% and purity of sugarcane juice by 0.8% on account of increased leaf sulphur content as compared with that under control. The application of Fe-EDDHA or gypsum had little effect on the quality of sugarcane juice. Effect of ferrous sulphate was intermediate between that of sulphur and gypsum. A study of the relationship between sulphur content of leaves and juice characteristics showed that every 1% increase in sulphur content of leaves increased sugar content in cane juice by 0.038%, recovery of sugar by 0.038% and purity of juice by 0.033%.     

Induction of flowering in Lemna paucicostata,a short-day plant,by chelating agents and iron

Summary Lemna paucicostata is a short-day plant which normally flowers only in a medium supplemented with EDTA or EDDHA. On a molar basis EDDHA is more effective for induction of flowering. The chelating agent can be replaced by high concentrations of ferric citrate in the medium. Simultaneous supply of both EDDHA and a high level of ferric citrate results in flowering even under long days.     

Effect of gelling agents and antibiotics on adventitious bud regeneration from In vitro leaves of pear

Summary The effect of the type of gelling agent and of several antibiotics on the adventitious bud regeneration from in vitro leaves was tested on eight pear genotypes. The use of gellan gum (Phytagel™) in the medium instead of agar had a very strong positive effect on the rate of adventitious bud regeneration for all pear genotypes tested in this study. This gelling agent induced faster cell divisions than agar, thus more callus was produced on wound sites and subsequently more buds regenerated. Incubation on gellan gum medium during the first 20 d of bud induction was sufficient to induce a stimulatory effect on regeneration and limited the production of hyperhydric buds. In the prospect of Agrobacterium transformation, the effect of several antibiotics was tested. Cefotaxime (200 mg/l) plus ticarcillin/clavulanic acid (100 mg/l) could be used in the culture medium without affecting the frequency of bud regeneration. The inhibition of bud regeneration was obtained with different kanamycin concentrations according to the gelling agent in the medium. On gellan gum medium, a concentration of 100 mg/l of kanamycin was suitable. These conditions can be recommended for experiments on Agrobacterium-mediated transformation of pear, where bacterial inoculation and presence of antibiotics generally reduce and delay bud regeneration.     

NbALD1 mediates resistance to turnip mosaic virus by regulating the accumulation of salicylic acid and the ethylene pathway in Nicotiana benthamiana

AGD2-LIKE DEFENCE RESPONSE PROTEIN 1 (ALD1) triggers plant defence against bacterial and fungal pathogens by regulating the salicylic acid (SA) pathway and an unknown SA-independent pathway. We now show that Nicotiana benthamiana ALD1 is involved in defence against a virus and that the ethylene pathway also participates in ALD1-mediated resistance. NbALD1 was up-regulated in plants infected with turnip mosaic virus (TuMV). Silencing of NbALD1 facilitated TuMV infection, while overexpression of NbALD1 or exogenous application of pipecolic acid (Pip), the downstream product of ALD1, enhanced resistance to TuMV. The SA content was lower in NbALD1-silenced plants and higher where NbALD1 was overexpressed or following Pip treatments. SA mediated resistance to TuMV and was required for NbALD1-mediated resistance. However, on NahG plants (in which SA cannot accumulate), Pip treatment still alleviated susceptibility to TuMV, further demonstrating the presence of an SA-independent resistance pathway. The ethylene precursor, 1-aminocyclopropanecarboxylic acid (ACC), accumulated in NbALD1-silenced plants but was reduced in plants overexpressing NbALD1 or treated with Pip. Silencing of ACS1, a key gene in the ethylene pathway, alleviated the susceptibility of NbALD1-silenced plants to TuMV, while exogenous application of ACC compromised the resistance of Pip-treated or NbALD1 transgenic plants. The results indicate that NbALD1 mediates resistance to TuMV by positively regulating the resistant SA pathway and negatively regulating the susceptible ethylene pathway.     

Effect of certain chelating agents on the antibacterial action of silver nitrate

EDTA and EGTA when used in conjunction with AgNO3 enhanced the antibacterial action of the latter significantly, so that strains of Klebsiella pneumoniae and Staphylococcus aureus resistant to 70 micrograms/ml of AgNO3 were observed to became sensitive to 10 micrograms/ml of this compound. The synergistic effect of EDTA appears to be due to a mechanism other than the removal of lipopolysaccharide from outer membrane, as its effect could be observed in even non-LPS containing gram positive S. aureus cells. Penicillamine, another potent chelator had an opposite effect so that it decreased the toxicity of silver ions.     

Stimulation and attenuation of induced resistance by elicitors and inhibitors of chemical induction in tomato (Lycopersicon esculentum) foliage

Elicitors and inhibitors of chemical induction were used to manipulate the activities of several putative defense-related proteins in leaves of the tomato, Lycopersicon esculentum Mill. The four presumptive defenses manipulated were proteinase inhibitors, polyphenol oxidase, peroxidase, and lipoxygenase. The elicitors used were jasmonic acid, methyl jasmonate, ultraviolet light, and feeding by larvae of the noctuid, Helicoverpa zea Boddie; the inhibitors used were salicylic acid and acetylsalicylic acid. These chemical manipulations were combined with short-term growth assays using larvae of the generalist noctuid, Spodoptera exigua Hubner, in order to assess the relative roles of the proteins in induced resistance to S. exigua. When activities of proteinase inhibitors and/or polyphenol oxidase in leaf tissue were high (e.g., in damaged or elicited plants), growth rates of larvae of S. exigua were low; when activities of polyphenol oxidase and proteinase inhibitors were low (e.g., in undamaged or damaged, inhibited plants), growth rates of larvae were high. In contrast, high activities of peroxidase and lipoxygenase were not associated with decreases in suitability of leaf tissue for S. exigua. The association of high levels of proteinase inhibitors and polyphenol oxidase with resistance to S. exigua – irrespective of the presence or absence of damage – strongly implicates these proteins as causal agents in induced resistance to S. exigua.     

UV-B and UV-C induction of NADP-malic enzyme in tissues of different cultivars of Phaseolus vulgaris (bean)

The effects of the treatment of different tissues of three bean cultivars (Pinto, Vilmorin and Arroz) with ultra‐violet (UV) UV‐B and UV‐C radiation and red light on the activity, quantity and RNA levels of NADP‐malic enzyme (NADP‐ME) were determined. Exposure to UV‐B radiation for 8 h caused a marked increase of NADP‐ME from leaves, stems and roots in the three cultivars studied. A similar induction was observed in the leaves and stems after 8 h of exposure under UV‐C, but not in the roots, suggesting that a different signal might be acting to induce the expression of NADP‐ME after UV‐B and UV‐C exposure. In contrast, red light was ineffective in inducing NADP‐ME in either tissue, so the regulation of the expression of this enzyme is phytocrome‐independent. The activity of superoxide dismutase, ascorbate peroxidase, catalase and peroxidase was also different in plants treated with UV‐B, UV‐C and photosynthetically active radiation, suggesting that various pathways may be acting in the regulation of these enzymes by UV‐B and UV‐C. Reactive oxygen species (ROS) were also required for UV‐B induction of NADP‐ME, as the addition of ascorbic acid before UV‐B treatment prevented NADP‐ME induction, whereas salicylic acid was not effective in inducing the enzyme, showing that NADP‐ME induction by UV‐B is ROS dependent but salicylic acid independent.