Accumulation and distribution of iron, cadmium, lead and nickel in cucumber plants grown in hydroponics containing two different chelated iron supplies

Cucumber plants grown in hydroponics containing 10 μM Cd(II), Ni(II) and Pb(II), and iron supplied as Fe(III) EDTA or Fe(III) citrate in identical concentrations, were investigated by total-reflection X-ray fluorescence spectrometry with special emphasis on the determination of iron accumulation and distribution within the different plant compartments (root, stem, cotyledon and leaves). The extent of Cd, Ni and Pb accumulation and distribution were also determined. Generally, iron and heavy-metal contaminant accumulation was higher when Fe(III) citrate was used. The accumulation of nickel and lead was higher by about 20% and 100%, respectively, if the iron supply was Fe(III) citrate. The accumulation of Cd was similar. In the case of Fe(III) citrate, the total amounts of Fe taken up were similar in the control and heavy-metal-treated plants (27-31 μmol/plant). Further, the amounts of iron transported from the root towards the shoot of the control, lead- and nickel-contaminated plants were independent of the iron(III) form. Although Fe mobility could be characterized as being low, its distribution within the shoot was not significantly affected by the heavy metals investigated.     

Ni-induced Changes in Nitrate Assimilation and Antioxidant Metabolism of Verbascum olympicum Boiss.: Could the Plant be Useful for Phytoremediation or/and Restoration Purposes?

Verbascum olympicum Boiss. (Scrophulariaceae) were studied as a candidate plant for remediating the Ni polluted soils. The metabolic responses, such as nitrate assimilation (nitrate reductase and glutamine synthetase activity) and antioxidant system activity [superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX) activity], of this species exposed to nickel in Hoagland's nutrient medium were investigated as remediation performance parameters. The accumulation of nickel and the variations in the content of some elements (B, Cu, Fe, Mg, Mn, Mo and Zn) and some growth parameters, such as the water content, biomass production, and contents of chlorophyll and soluble protein, were also examined. The accumulation of Ni in both the roots and leaves varied depending on the exposure times and doses. Increased oxidative stress was suggested by the increases in the activities of SOD, CAT and APX. Although some element contents were inhibited by Ni treatments, these inhibitory effects was decreased depending on the time, and even these elements are accumulated in roots. These results are the novelties in the use of this species in biotechnology.     

Salinity attenuates nickel-accumulating capacity of <Emphasis Type="Italic">Atropa belladonna</Emphasis> L. plants

Comparative analysis of growth and composition of Atropa belladonna L. plants was performed after separate and combined additions of NaCl and NiCl₂ to the nutrient medium. Plants were grown in water culture on modified Johnson solution for 8 weeks until the formation of the fifth leaf pair. Thereafter, NiCl₂ was introduced at final concentrations of 100 and 150 μM into the medium either separately or in combination with 100 mM NaCl. After completing the 7-day treatment with Ni ions, the plants' weight and the content of water and photosynthetic pigments were determined. The content of Ni, free polyamines (putrescine, spermidine, spermine), and atropine was determined in plant roots and leaves, whereas the content of Fe, proline, and malondialdehyde (MDA) was examined in leaves only. The distribution of Ni in various tissues was inspected using the dimethylglyoxime method. The presence of NiCl₂ in growth media diminished the increments in fresh weight of shoots and roots; lowered the content of water, pigments, and iron in leaves; and initiated chlorosis. The leaves of Ni-treated plants accumulated larger amounts of atropine, putrescine, proline, and MDA with respect to the control levels of these compounds. In contrast to the action of Ni alone, the combined application of NaCl and NiCl₂ was followed by the increased content of water and pigments in leaves. The presence of NaCl in the medium restricted the entry of Ni into roots and diminished the levels of MDA and proline in leaves. After growing the plants in the presence of 100 and 150 μM NiCl₂, nickel was located in the root outer cortex and the rhizoderm. In plants treated with 150 μM NiCl₂, nickel was also observed in tissues of the central cylinder, mostly in the pericycle, phloem, and xylem. In plants grown in the presence of 150 μM NiCl₂ and 100 mM NaCl, the decreased accumulation of nickel was noted in the tissues of the central cylinder in the root hair zone. Thus, the combined action of Ni and moderate salinity reduced nickel accumulation in roots and aboveground organs of A. belladonna plants. The reduced Ni content in plants mitigated the toxic effect of Ni present in the medium. This was manifested in stabilization of leaf water status, an increase in the content of photosynthetic pigments, and alleviation of oxidative stress, which was assessed from the content of low-molecular organic compounds exhibiting stress-protective and antioxidant action (proline, MDA, free polyamines, and atropine).     

Contribution of putrescine degradation to proline accumulation in soybean leaves under salinity

Proline accumulation was studied in the leaves of Glycine max (L.) Merr. subjected to salt stress in the presence of aminoguanidine (AG, a specific inhibitor of diamine oxidase, DAO) and exogenous putrescine (Put). Both DAO activity and proline content were increased while endogenous Put content was decreased in soybean leaves under 50 to 150 mM NaCl. There was a negative correlation between proline accumulation and endogenous Put content. The addition of AG during NaCl stress inhibited DAO activity, caused Put accumulation and a 15 to 20 % decrease in proline content. Application of 1 mM Put to NaCl solution markedly increased proline content. The promotive effect of Put application could be alleviated by the treatment with Put plus AG. Moreover an application of AG had no effect on proline accumulation in soybean seedlings grown under normal condition. These results indicate that the quantitative contribution of Put degradation to proline formation is 15 to 20 %.     

Phytoremediation potential of <Emphasis Type="Italic">Amaranthus</Emphasis> hybrids: Antagonism between nickel and iron and chelating role of polyamines

Three amaranth hybrids (Amaranthus paniculatus f. cruentus (Vishnevyi dzhem), A. paniculatus (Bronzovyi vek), and A. caudatus f. iridis (Izumrud) were grown in the climate-controlled chamber on Jonson nutrient medium supplemented with 2 μM Fe³⁺-EDTA. When plants developed 5–6 true leaves (six-week-old plants), NiCl₂ was added to medium to final concentrations of 0 (control), 50, 100, 150, 200, and 250 μM. In 6 days, the increment in biomass of young and mature leaves, stems, and roots, and also the contents of Ni and Fe in them were measured. The red leaf amaranth hybrid Vishnevyi dzhem manifested the highest phytoremediation potential. i.e., the highest capacity for Ni accumulation in the shoots and the most pronounced symptoms of Fe deficit. In the presence of 150 and 250 μM NiCl₂ in medium, the shoots of these plants contained about 2 and 4 mg Ni/g dry wt, respectively. In experiments with Fe deficit in plants grown for a week in the presence of NiCl₂ (0, 25, 50, 75, and 100 μM), it was established that all tested nickel concentrations suppressed iron reduction in intact roots, which is catalyzed by ferric-chelate reductase, and this may underlie the antagonism between the two metals. In the presence of 50 μM NiCl₂ in medium and 2 μM Fe³⁺ (Fe deficit) and especially 100 μM Fe³⁺ (Fe excess), the content of MDA and proline in leaves increased and superoxide dismutase was activated; this indicates a development of oxidative stress. Leaf treatment with polyamines (putrescine or spermidine) with aminoguanidine (the inhibitor of H₂O₂ generation at polyamine oxidation) and with 1,3-diaminopropane led to the increase in nickel accumulation in leaves but did not result in the appearance of any signs of injury. This confirms our previous suggestion that polyamines manifest their protectory action as Ni chelators and detoxicants.     

Proline protects <Emphasis Type="Italic">Atropa belladonna</Emphasis> plants against nickel salt toxicity

Atropa belladonna L. plants were grown in water culture for 8 weeks before the nutrient medium was supplemented with NiCl₂ to final concentrations of 0 (control treatment), 50, 100, 150, 200, 250, and 300 μM. After 4 days of plant growing in the presence of nickel chloride, the content of water, proline, Ni, Fe, free polyamines, as well as lipid peroxidation rates were measured. The addition of 100–150 μM Ni to the medium significantly reduced the fresh weight increments and water content in comparison with these parameters for untreated plants; 200 μM Ni caused serious, although nonlethal damage to the plants, whereas 250 and 300 μM Ni proved to be lethal. In the aboveground organs, the major part of Ni was accumulated in the apical leaves. When the plants were treated with 200 μM Ni, the Ni content in apical leaves was 220 μg/g dry wt, while Ni content in roots reached 1500 μg/g dry wt. The treatment of plants with proline in the presence of 200 μM Ni inhibited Ni accumulation in tissues. The proline-treated plants exhibited elevated iron content in leaves and especially in roots and were characterized by comparatively low rates of lipid peroxidation and by sustained leaf water status. When 200 μM Ni was applied, the content of free putrescine decreased, while the contents of spermine and spermidine in leaves increased appreciably with respect to the control values. The toxic effect of nickel was accompanied not only by an enhanced accumulation of high- molecular-weight polyamines but also by their oxidative degradation, which was evident from the 14-fold increase in the content of 1,3-diaminopropane. The protective effect of exogenous proline in the presence of high nickel concentrations was manifested in lowered lipid peroxidation rates, alleviation of iron deficiency, and in retarded oxidative degradation of polyamines.     

Dry Matter and Leaf Structure in Young Wheat Plants as Affected by Cadmium, Lead, and Nickel

The effects of 1 mM cadmium, lead and nickel on dry mass, Cd, Pb, and Ni contents, and changes in leaf structure in young wheat plants were studied. In leaves, Cd content was highest, followed by Pb and Ni, in roots Cd content was also highest, but followed by Ni and Pb. Roots accumulated considerably larger amounts of the three heavy metals than leaves. Largest reductions of leaf and root mass were obtained with Cd. Pb and Ni effects were almost equal. Ni excess had a strong negative effect on mesophyll thickness, while Cd mostly reduced the number and size of vascular bundles and vessel diameter. High Pb reduced the diameter of vessels causing their different deformations. This revised version was published online in July 2006 with corrections to the Cover Date.     

Polyamines content and physiological and biochemical responses to ladder concentration of nickel stress in Hydrocharis dubia (Bl.) Backer leaves

Influence of ladder concentration of nickel (Ni) on the leaves of Hydrocharis dubia were studied after 3 days treatment. The accumulation of Ni, the content of polyamines, proline, malondialdehyde (MDA) and soluble protein, as well as the activities of superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD) in the leaves were investigated. The result indicated that the toxicity of Ni manifested in respective aspect of physiological and biochemical characters. Significant increase of Ni concentration in the leaf tissue was observed, which was concentration dependent. Visible symptoms of Ni toxicity: chlorosis and necrosis occurred following the 3rd day. Meantime, treatment with Ni resulted in the increase in the generation rate of O₂^•− in the leaves. SOD and CAT activities decreased significantly in response to Ni treatment, it was possibly the reason of accumulation of O₂^•−. However, a several-fold decrease in POD activities was found. Our results indicated that because of prolonged increases in O₂^•− level, oxidative damage, measured as the level of lipid peroxidation, occured in the leaves of Ni treated fronds. The changes of the content of polyamines (PAs) were also investigated in the leaves of Hydrocharis dubia. Ni treatment significantly increased the putrescine (Put) level and lowered spermidine (Spd) and spermine (Spm) levels, thereby significantly reducing the ratio of free (Spd + Spm)/Put in leaves, which has been considered as the signal under stress. Although the trend that PS-conjugated PAs and PIS-bound PAs changed the same as free PAs, they changed in more less extent.     

Effects of exogenously applied salicylic acid and putrescine alone and in combination with rhizobacteria on the phytoremediation of heavy metals and chickpea growth in sandy soil

The present attempt was made to study the role of exogenously applied salicylic acid (SA) and putrescine (Put) on the phytoremediation of heavy metals and on the growth parameters of chickpea grown in sandy soil. The SA and Put were applied alone as well as in combination with plant growth promoting rhizobacteria (PGPR). The PGPRs, isolated from the rhizosphere of chickpea, were characterized on the basis of colony morphology and biochemical traits through gram staining, catalase and oxidase tests, and identified by 16S-rRNA gene sequencing as Bacillus subtilis, Bacillus thuringiensis and Bacillus megaterium. The chickpea seeds were soaked in 24 h old fresh cultures of isolates for 2–3 h prior to sowing. The growth regulators (PGRs), SA and Put (150 mg/L), were applied to the seedlings as foliar spray at three-leaf stage. The result revealed that plants treated with SA and Put alone or in combination with PGPRs, significantly enhanced the accumulation of heavy metals in plant shoot. PGPR induces Ni accumulation in sensitive variety and Pb in both the varieties, the PGR in combination augment the bioremediation effects of PGPR and both sensitive and tolerant variety showed significant accumulation of Ni, Cd, and Pb. SA was more effective in accumulating Ni and Cd whereas, significant accumulation of Pb was recorded in Put. PGPRs further augmented the PGRs induced accumulation of heavy metals and macronutrients in chickpea shoot and in rhizosphere. SA increased the proline content of tolerant variety while decreasing the lipid peroxidation and proline content of the sensitive variety but decreased the stimulating effect of PGPR in proline production. Interactive effects of PGPR and PGRs are recommended for inducing phytoremediation in chickpea plants under drought stress.     

Exogenous proline effects on water relations and ions contents in leaves and roots of young olive

The ability of exogenous compatible solutes, such as proline, to counteract salt inhibitory effects was investigated in 2-year-old olive trees (Olea europaea L. cv. Chemlali) subjected to different saline water irrigation levels supplied or not with exogenous proline. Leaf water relations [relative water content (RWC), water potential], photosynthetic activity, leaf chlorophyll content, and starch contents were measured in young and old leaves. Salt ions (Na⁺, K⁺, and Ca²⁺), proline and soluble sugars contents were determined in leaf and root tissues. Supplementary proline significantly mitigated the adverse effects of salinity via the improvement of photosynthetic activity (Pn), RWC, chlorophyll and carotenoid, and starch contents. Pn of young leaves in the presence of 25 mM proline was at 1.18 and 1.38 times higher than the values recorded under moderate (SS1) and high salinity (SS2) treatments, respectively. Further, the proline supply seems to have a more important relaxing effect on the photosynthetic chain in young than in old leaves of salt-stressed olive plants. The differential pattern of proline content between young and old leaves suggests that there would be a difference between these tissues in distinguishing between the proline taken from the growing media and that produced as a result of salinity stress. Besides, the large reduction in Na⁺ accumulation in leaves and roots in the presence of proline could be due to its interference in osmotic adjustment process and/or its dilution by proline supply. Moreover, the lower accumulation of Na⁺ in proline-treated plants, compared to their corresponding salinity treatment, displayed the improved effect of proline on the ability of roots to exclude the salt ions from the xylem sap flowing to the shoot, and thus better growth rates.     

Phytoremediation of Cd, Cr, Cu, Mn, Fe, Ni, Pb and Zn from aqueous solution using Phragmites cummunis, Typha angustifolia and Cyperus esculentus

A comparative bioaccumulation pattern and ultra structural changes were studied in Phragmites cummunis, Typha angustifolia and Cyperus esculentus in mixed metals solution of cadmium (Cd), chromium (Cr), copper (Cu), iron (Fe), manganese (Mn), nickel (Ni), lead (Pb) and zinc (Zn). P. cummunis was observed to be a shoot accumulator for Cr, Fe, Mn, Ni, Pb, and Zn. However, T. angustifolia was found to be a root accumulator for Cd, Cr, Cu, Fe, Ni and Pb. In addition, C. esculentus also accumulated most of the tested heavy metals in the roots, while Mn and Fe were translocated up to leaves. Further, the long term metal treatment showed maximum accumulation of all heavy metals in P. cummunis followed by T. angustifolia and C. esculentus. Among heavy metals, Fe was accumulated maximum, i.e., >1000 microg g(-1) by all three plants. Simultaneously, the adverse effects on biochemical parameters were noted earlier in C. esculentus than T. angustifolia and P. cummunis. Ultra structural observation showed the cellular changes in wetland plants after longer exposure. Results revealed that P. cummunis and T. angustifolia had more potential for tested metals than C. esculentus. This study established that these wetland plants could be used for heavy metals phytoremediation from metal containing industrial wastewater.     

TL-DNA transformation decreases ABA level

The endogenous levels of ABA were measured in Agrobacterium rhizogenes A₄ T_l-DNA transformed oilseed rape (Brassica napus L. var. oleifera cv . Brutor and cv. Drakkar), cabbage (Brassica oleracea) . A₄ transformed tobacco ( Nicotiana tabacum cv. Xanthi) and their normal counterparts, using high performance liquid chromatography and enzyme-liked immunosorbent assay. Measurements were made on different plant tissues (i. e. floral stem, terminal bud, young leaf, mature leaf, root and root tips) and ABA levels were compared in unstressed and osmotically stressed oilseed rape plants (cv. Brutor). In unstressed Plants. in each of the 5 independent transformation events studied, a significant reduction (about 65% of control) in ABA concentration was observed in all transformed plants. When subjected to an osmotic stress, T_L transformed Brutor plants showed a higher ABA accumulation than untransformed plants. The change in ABA content as a consequence of T_L-DNA transformation is discussed with regard to phenotype, drought resistance and adaptability.     

Exogenous polyamines enhance copper tolerance of Nymphoides peltatum

The protective effects of polyamines (PAs) against copper (Cu) toxicity were investigated in the leaves of Nymphoides peltatum. Cu treatment increased the putrescine (Put) level and lowered spermidine (Spd) and spermine (Spm) levels, thereby reducing the (Spd+Spm)/Put ratio in leaves. Exogenous application of Spd or Spm markedly reversed these Cu-induced effects for all three PAs and partially restored the (Spd+Spm)/Put ratio in leaves. It also significantly enhanced the level of proline, retarded the loss of soluble protein, decreased the rate of O2*- generation and H2O2 content, and prevented Cu-induced lipid peroxidation. Furthermore, exogenous Spd and Spm reduced the accumulation of Cu and effectively maintained the balance of nutrient elements in plant leaves under Cu stress. These results suggest that exogenous application of Spd or Spm can enhance the tolerance of N. peltatum to Cu by increasing the levels of endogenous Spd and Spm as well as the (Spd+Spm)/Put ratio.     

Modulation of phytoremediation and plant growth by the treatment with PGPR,Ag nanoparticle and untreated municipal wastewater

The present attempt was made to determine the effects of untreated municipal wastewater (MW) on growth and physiology of maize and to evaluate the role of Ag nanoparticle and plant-growth-promoting rhizobacteria (PGPR) when interacting with MW used for irrigation. It was used for the isolation of PGPR. The isolates were identified and characterized based on the colony morphology, C/N source utilization pattern using miniaturized identification system (QTS 24), catalase (CAT) and oxidase tests, and 16S rRNA sequence analyses. The three PGPR isolates were Planomicrobium chinense (accession no. NR042259), Bacillus cereus (accession no. CP003187) and Pseudomonas fluorescens (accession no. GU198110). The isolates solubilized phosphate and exhibited antibacterial activities against pathogenic bacteria i.e., Staphylococcus aureus, Pseudomonas aeruginosa, Bacillus subtilis, Klebsiella pneumoniae and Escherichia coli and antifungal activities against Helminthosporium sativum and Fusarium solani. The untreated MW irrigation as well as Ag nanoparticle treatment resulted in significant accumulation of Ni in the rhizosphere soil. PGPR induced accumulation of Ni and Pb in the rhizosphere soil and maize shoot. Ag nanoparticle also caused Ni and Pb accumulation in maize shoot. Combined treatment with PGPR, Ag nanoparticle and MW resulted in decreased accumulation of Pb and Ni both in the rhizosphere soil and maize shoot. Combined treatment of Ag nanoparticle, MW and PGPR decreased Na accumulation and increased K accumulation. Ag nanoparticle increased Fe and Co accumulation but decreased Zn and Cu accumulation in MW treatment; in combined treatment, it reduced PGPR-induced accumulation of Co and Fe in the rhizosphere and Co accumulation in shoot. PGPR significantly increased root weight, shoot weight, root length, shoot length, leaf area, and proline, chlorophyll and carotenoid content of the maize plant. Ag nanoparticle also enhanced the leaf area, fresh weight, root length and antioxidant activities of maize. Treatment with Ag nanoparticle increased the gibberellic acid (GA) and abscisic acid (ABA) content of maize leaves but decreased the accumulation of GA in the presence of PGPR and MW.     

氮素形态和铁营养对玉米苗期生长及体内铁分布的影响

以玉米(Zea mays)品种‘豫玉-22’为材料,采用营养液培养方法,研究了低铁和正常供铁条件下供应不同形态氮素对玉米苗期生长及体内铁分布的影响。结果表明:(1)与低铁介质相比,常铁介质增加了各氮素处理玉米幼苗的株高、地上部干重、全株干重,降低了根冠比,其中硝态氮处理表现得尤其突出;与供应硝态氮(NO3--N)相比,增施铵态氮(1/2 NO3--N 1/2 NH4 -N,NH4 -N)能明显促进低铁介质中玉米生长,但在常铁介质下作用不明显。(2)相比于低铁介质,正常供铁显著提高了相应处理玉米新叶叶绿素含量及净光合速率;2种供铁介质中,NH4 -N处理的新叶叶绿素含量以及净光合速率均高于其它氮素处理。(3)相比于低铁介质,正常供铁处理总体上增加了玉米各部分活性铁含量和全铁含量,对NO3--N处理的新叶活性铁含量增加尤其明显;2种供铁介质中,NH4 -N均有利于提高新叶活性铁含量和植株地上部全铁含量。(4)玉米新叶活性铁含量不仅与其叶绿素含量显著正相关(r=0.979**),也与叶片净光合速率显著正相关(r=0.950**)。研究发现,供铁状况显著影响玉米新叶的叶绿素含量及其净光合速率且与供氮形态存在互作;供应铵态氮有利于提高缺铁条件下玉米新叶活性铁含量,增强玉米植株的光合能力,进而促进其正常生长。     

Significance of phenols in cadmium and nickel uptake

The effects of 2-aminoindane-2-phosphonic acid (AIP), a potent phenylalanine ammonia-lyase (PAL) inhibitor, on the accumulation of cadmium and nickel in chamomile (Matricaria chamomilla) were examined in this study. In vitro assay of AIP effect showed a 90% reduction in PAL activity. In plants cultured for 7 days in Cd or Ni solutions with AIP, PAL activity was higher in both shoots and roots (in comparison with metals without AIP), and was correlated with changes in free phenylalanine content. Individual amino acids were both positively and negatively affected by AIP, with the accumulation of tyrosine and proline showing increases in some variants. Contents of soluble phenols and flavonoids were not considerably affected, while amounts of coumarin-related compounds, cell wall-bound phenols and phenolic acids were substantially reduced in AIP-treated variants. Lignin accumulation decreased in controls and increased in Cd variants in response to AIP. Shoot Cd content was depleted, but shoot Ni was elevated by AIP. Total root content of Cd and Ni decreased in +AIP variants. AIP also caused more expressive changes in hydrogen peroxide and superoxide content in Cd than in Ni variants. Our results indicate that phenols have important roles in the uptake of Cd and Ni. The present findings are discussed in the context of available data regarding AIP's effect on phenols.     

Selective transport of zinc, manganese, nickel, cobalt and cadmium in the root system and transfer to the leaves in young wheat plants

BACKGROUND AND AIMS: The uptake, translocation and redistribution of the heavy metals zinc, manganese, nickel, cobalt and cadmium are relevant for plant nutrition as well as for the quality of harvested plant products. The long-distance transport of these heavy metals within the root system and the release to the shoot in young wheat (Triticum aestivum 'Arina') plants were investigated. METHODS: After the application of 65Zn, 54Mn, 63Ni, 57Co and 109Cd for 24 h to one seminal root (the other seminal roots being excised) of 54-h-old wheat seedlings, the labelled plants were incubated for several days in hydroponic culture on a medium without radionuclides. KEY RESULTS: The content of 65Zn decreased quickly in the labelled part of the root. After the transfer of 65Zn from the roots to the shoot, a further redistribution in the phloem from older to younger leaves was observed. In contrast to 65Zn, 109Cd was released more slowly from the roots to the leaves and was subsequently redistributed in the phloem to the youngest leaves only at trace levels. The content of 63Ni decreased quickly in the labelled part of the root, moving to the newly formed parts of the root system and also accumulating transiently in the expanding leaves. The 54Mn content decreased quickly in the labelled part of the root and increased simultaneously in leaf 1. A strong retention in the labelled part of the root was observed after supplying 57Co. CONCLUSIONS: The dynamics of redistribution of 65Zn, 54Mn, 63Ni, 57Co and 109Cd differed considerably. The rapid redistribution of 63Ni from older to younger leaves throughout the experiment indicated a high mobility in the phloem, while 54Mn was mobile only in the xylem and 57Co was retained in the labelled root without being loaded into the xylem.     

6-BA+B9对龙眼花芽生理分化期内源多胺含量变化的影响

在龙眼花芽生理分化期喷施6-BA 200 mg/L+B₉ 2000 mg/L,跟踪测定其内源多胺含量变化。研究结果表明,龙眼花芽生理分化期内源腐胺(Put)、亚精胺(Spd)和精胺(Spm)含量均出现积累,喷施6-BA+B₉能明显提高内源多胺含量,特别是Put和Spd的含量。内源多胺与花芽分化有一定的内在联系,生长调节剂对花芽分化的调控有可能通过多胺来实现或协同作用。     

Nickel-induced Inhibition of Wheat Root Growth is Related to H2O2 Production, but not to Lipid Peroxidation

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.     

Influence of Ni Supply on Growth and Nitrogen Metabolism ofBrassica napusL. Grown with NH4NO3or Urea as N Source

The significance of nickel (Ni), which is essential for ureaseactivity, for growth and nitrogen (N) metabolism ofBrassicanapusgrown in nutrient solution with either NH₄NO₃or urea assole N source was investigated. Although Ni contents were below25 µg kg^-1d. wt, growth of plants relying on NH₄NO₃wasnot affected by the Ni status. However, supplementing the growthmedium with 0.04 µMNi enhanced dry matter production ofurea-grown plants significantly. Urease activity was significantlyreduced in leaves and roots of plants grown without supplementaryNi irrespective of N source. Plants grown with urea withoutadditional Ni accumulated large amounts of urea and had loweramino acid contents indicating impaired usage of the N supplied,while those grown with NH₄NO₃under Ni-deprived conditions accumulatedendogenous urea in their older leaves. It is suggested thatNi may not be strictly essential for plants receiving mineralN, or that the critical level is well below 25 µg kg^-1d.wt. These results confirm that Ni is required for urease activityand thus for growth of plants on urea-based media, as well asfor recycling endogenous urea.Copyright 1999 Annals of BotanyCompany. Brassica napusvar.annua, amino acids, N nutrition, nickel, spring rape, urea, urease activity.