Evaluation of copper-induced stress on eggplant (Solanum melongena L.) seedlings at the molecular and population levels by use of various biomarkers

Heavy-metal contamination is an important environmental problem in the world. It is known that high concentrations of heavy metals cause toxic damage to cells and tissues. In this study the effects of copper (Cu(2+)) contamination were determined at the molecular and population levels in eggplant (Solanum melongena L.) seedlings exposed to various concentrations of the metal ion. Inhibition of root growth, reduction in dry weight and total soluble protein content in the roots of eggplant seedlings were observed with increasing Cu(2+) concentrations. In ecotoxicology, analysis by random amplification of polymorphic DNA (RAPD) has been applied as a suitable biomarker assay for plants. For the RAPD analyses, nine RAPD primers were found to produce unique polymorphic band patterns and were subsequently used to produce a total of 80 and 168 bands in the roots of untreated and treated eggplant seedlings, respectively. The changes in RAPD profiles after Cu(2+) contamination were considered as variations, i.e. as gain and/or loss of bands compared with control seedlings. These results suggest that changes in genomic template stability could be detected with RAPD profiles and this result could be compared with the growth, dry weight and total soluble protein content of the seedlings grown at various Cu(2+) concentrations. The measurements of parameters at the molecular and population levels are fundamental to accumulate valuable information and to understand clearly the effect of a contaminant on an organism in ecotoxicology.     

小麦不同生育时期Cd、Cr、Pb污染监测指标体系

以小麦为供试材料,分别采用发芽试验、溶液培养、土柱栽培等毒理试验方法,研究了小麦萌芽期、幼苗期及成株期受重金属污染毒害的指标体系。结果表明,①小麦根伸长抑制率可作为萌芽期重金属污染评价的一项生物指标;Cd、Cr、Pb对小麦根生长的7d半效应浓度(EC50)值分别为1.39、0.20mmo.lL-1和2.75mmol.L-1,据此得到3种重金属对小麦同一性状的毒性次序为CrCdPb;此外各性状抑制率与胁迫浓度的关系可用双曲线模型y=x/(a+x/100)或指数曲线模型y=a(1-exp(-bx))较好模拟。②Cd、Cr、Pb单一污染胁迫对小麦幼苗性状的毒性次序均以影响叶面积和冠部干重为主,表明叶面积和冠部干重为幼苗期污染监测的敏感指标;重金属对除根干重外所有性状的毒性次序:CrCdPb,该毒性次序是根据引起50%抑制的临界浓度即EC50值确定的;各性状抑制率与胁迫浓度的关系可用直线模型、或双曲线模型、或指数曲线模型较好模拟。③重金属单一污染胁迫造成小麦籽粒产量下降幅度是CdCrPb;二元互作对产量影响的重要性次序为CdCrCdPbCrPb;在Cd、Cr、Pb复合污染胁迫条件下,穗数可以作为成株期重金属污染监测的首选指标。以上指标可为农田小麦重金属污染的监测和综合治理提供一些理论依据。     

Mineral nutrient imbalance, total antioxidants level and DNA damage in common bean (Phaseolus vulgaris L.) exposed to heavy metals

The present study aimed to analyze the biological effects induced by bioaccumulation of metals in common bean (Phaseolus vulgaris L.). Effects of mineral nutrient imbalance, total antioxidants level and DNA damage induced by accumulation of heavy metals, were investigated in bean seedlings treated with two selected metal concentrations for 7 days. Metal content is analyzed by inductively coupled plasma – atomic emission spectrometer (ICP-AES), for total antioxidants level assessment the Ferric-Reducing Antioxidant Power (FRAP) assay is used and Random Amplified Polymorphic DNA (RAPD) method was applied for investigation of DNA damages. The increasing metal concentration in the treatment medium changed synchronously metal content in samples, and decreased total antioxidant activity in all samples with exception only for samples treated with Ni and Cd. The obtained “DNA fingerprints” demonstrated that the increasing metal concentrations induced changes in RAPD profiles (disappearance and/or appearance of bands in comparison with untreated control samples). The highest number of missing bands was observed in samples treated with zinc (total 4 bands) and nickel (total 4 bands) at both concentrations. These results suggested that mineral nutrient imbalance is involved in changes of antioxidant levels and DNA damages of the seedlings, which may help to understand the mechanism of metal toxicity in plants.     

Effect of Increasing Concentrations of Lead and Cadmium on Cucumber Seedlings

The effect of lead and cadmium on biomass accumulation of cucumber seedlings (Cucumis sativus L.) as well as the contents of abscisic acid (ABA), free proline and soluble proteins in leaves were studied. Seedlings were subjected to lead nitrate or cadmium bromide in low concentrations (1 – 5 µM) for 1, 4 or 7 d, and then to the action of the same substances in high concentrations (500 – 1000 µM). The pretreatments of the seedlings with heavy metals in low concentrations enabled them to tolerate the subsequent high concentrations of cadmium and lead without injury. The plant responses to heavy metal treatment were accompanied by the accumulation of ABA, free proline and soluble proteins in leaf tissues.     

Biochemical and RAPD Analysis of Hibiscus rosa sinensis Induced by Heavy Metals

The present study was designed to assess the effects of three different metals (cadmium, lead, and zinc) at the same concentrations on Hibiscus rosa sinensis during metal uptake. The effects of different metals at the same concentrations were assessed on biomass, root-shoot length, and biochemical parameters like chlorophyll and antioxidant enzymes like SOD and CAT to establish the tolerance potential and toxic effects on plants in different metals. The accumulation of metals by plants was found to be in the following order: Zn > mixed metals > Cd > Pb, where Zn was accumulated approximately 79.6% in plant tissues. Plants removed from Cd showed more enzyme activities than the other two metals. DNA stability was investigated by a Random Amplified Polymorphic DNA (RAPD) technique, which demonstrated that the samples in Cd and mixed metal showed similar trends, whereas samples in Zn and Pb showed similar band intensity to the control. Results suggested that Cd and/or heavy metal stress influences antioxidant status and also induces DNA changes during remediation. Therefore, these studies could be a useful biomarker assay for better treatment for metals’ remediation from soil by means of phytoremediation.     

一氧化氮对水分胁迫下玉米种子萌发及幼苗生理特性的影响

以0.4mol/L的甘露醇(M)模拟水分胁迫状况,研究了外源一氧化氮(NO)供体硝普钠(SNP)对水分胁迫下玉米种子萌发、幼苗生长和生理特性的影响。结果表明:(1)水分胁迫下,玉米种子萌发和幼苗生长受到抑制,叶片丙二醛(MDA)含量、质膜相对透性、脯氨酸含量均显著增加;(2)SNP能显著提高水分胁迫下玉米种子的发芽率、发芽势、发芽指数和活力指数,增加玉米幼苗的根长、茎长、根重和整株干重,抑制水分胁迫下玉米幼苗叶片MDA含量的上升,降低叶片质膜相对透性,降低脯氨酸含量。其中以100μmol/L和200μmol/LSNP对水分胁迫的缓解效果最佳。     

三唑酮浸种后黄瓜幼苗的生理生化变化

黄瓜以一定浓度的三唑酮浸种后,幼苗的根长,株高受到明显抑制,但增大了根重、根冠比、子叶游离氨基酸含量及子叶呼吸速率,同时降低了子叶可溶性糖含量,30d苗龄第1、2片真叶中叶绿素、蛋白质含量、POD、CAT活力增有不同程度的提高,因此表现出一定的壮苗作用。其中50μmol/L对壮苗是最佳的,但高浓度对幼苗生长不利。     

Autotoxicity in cucumber (<Emphasis Type="Italic">Cucumis sativus</Emphasis> L.) seedlings is alleviated by silicon through an increase in the activity of antioxidant enzymes and by mitigating lipid peroxidation

Autotoxicity in plants limits their growth and that of nearby plants of the same species, which has obvious implications in crop yield and quality. Silicon (Si) has been shown to increase plant tolerance to autotoxic stress. However, the physiological mechanisms underlying the effects of Si in alleviating autotoxicity during germination in cucumber (Cucumis sativus L.) are unknown. Cinnamic acid derivatives, such as 3-phenylpropionic acid (PA), are a class of autotoxins present in cucumber root exudates. Our objective was to investigate Si-induced autotoxic stress tolerance in cucumber seedlings by focusing on the effects of Si on the induction of antioxidant defense pathways. We found that PA treatment significantly reduced seed germination, radicle length, lateral root number, fresh weight, AsA and GSH contents, and the activities of SOD, CAT, and APX in cucumber seedlings, while it increased membrane permeability and levels of MDA, proline, O₂^-, and H₂O₂. Application of Si enhanced growth of PA-treated plants and significantly increased germination rate, radicle length, lateral root number, fresh weight, AsA and GSH levels, and SOD, CAT, POD, and APX activities. These results suggest that exogenous Si alleviates autotoxicity caused by PA during seed germination by increasing antioxidant enzyme activities and mitigating lipid peroxidation.     

Assessment of heavy metal induced stress responses in pea (Pisum sativum L.)

Exposure of plants to heavy metals severely affects their growth and physiological processes. Nevertheless, different plants show variable responses to different heavy metals, generally in a concentration-dependent manner. In this study, phytotoxic effects of cadmium (Cd), cobalt (Co) and lead (Pb) applied as chlorides at concentration 500, 750, 1000 and 1250 ppm were evaluated on seed germination, early seedling growth and dry biomass of pea (Pisum sativum L.). A lower concentration (500 ppm) of Pb promoted seed germination but declined other growth parameters. Higher concentration had a phytotoxic influence on the pea. Cd and Co severely affected germination and seedling growth of pea resulting in complete failure of germination and seedling growth at higher metal concentration. Tolerance index (TI) calculated for seed germination and dry biomass indicated that tested plant had zero tolerance to 1250 ppm of Cd as well as 750 ppm and higher concentrations of Co. The order of heavy metals for their phytotoxic effects was Co > Cd > Pb. The study suggests that P. sativum is relatively tolerant to Pb but highly sensitive to Co and Cd.     

重金属对土壤中萝卜种子发芽与根伸长抑制的生态毒性

高等植物是生态系统中的基本组成部分。一个平衡、稳定的生态系统生产健康、优良的高等植物。反之 ,一个不稳定或受到外来污染的生态系统 ,对高等植物的生长可带来不利和可见的负面影响。因此 ,利用高等植物的生长状况监测土壤污染程度 ,是从生态学角度衡量土壤健康状况 ,评价土壤质量的重要方法之一[4 ,6] 1) 。土壤生态毒理学评价方法是对化学分析方法的重要补充。目前已建立的高等植物毒理试验有三种方法 ,即 1根伸长试验 ;2种子发芽试验 ;3早期植物幼苗生长试验[3 ,5,6,10 ] 。最初 ,这类试验主要用于纯化学品的毒性检验 ,但随着对土壤…     

Boron toxicity is alleviated by hydrogen sulfide in cucumber (Cucumis sativus L.) seedlings

Boron (B) is an essential micronutrient for plants, which when occurs in excess in the growth medium, becomes toxic to plants. Rapid inhibition of root elongation is one of the most distinct symptoms of B toxicity. Hydrogen sulfide (H₂S) is emerging as a potential messenger molecule involved in modulation of physiological processes in plants. In the present study, we investigated the role of H₂S in B toxicity in cucumber (Cucumis sativus) seedlings. Root elongation was significantly inhibited by exposure of cucumber seedlings to solutions containing 5 mM B. The inhibitory effect of B on root elongation was substantially alleviated by treatment with H₂S donor sodium hydrosulfide (NaHS). There was an increase in the activity of pectin methylesterase (PME) and up-regulated expression of genes encoding PME (CsPME) and expansin (CsExp) on exposure to high B concentration. The increase in PME activity and up-regulation of expression of CsPME and CsExp induced by high B concentration were markedly reduced in the presence of H₂S donor. There was a rapid increase in soluble B concentrations in roots on exposure to high concentration B solutions. Treatment with H₂S donor led to a transient reduction in soluble B concentration in roots such that no differences in soluble B concentrations in roots in the absence and presence of NaHS were found after 8 h exposure to the high concentration B solutions. These findings suggest that increases in activities of PME and expansin may underlie the inhibition of root elongation by toxic B, and that H₂S plays an ameliorative role in protection of plants from B toxicity by counteracting B-induced up-regulation of cell wall-associated proteins of PME and expansins.     

Alteration in growth and peroxidase activity by heavy metals in Phaseolus seedlings

The aim of the present work was to see the effect of mercury and chromium on elongation growth of phaseolus seedlings and changes in chlorophyll content. Phaseolus seedlings were treated with two different concentrations of two heavy metals viz. mercury (0.05 mM and 0.4 mM HgCl₂, and chromium (0.5 mM and 1.0 mM K₂Cr₂O₇). Both mercury and chromium inhibited root and hypocotyl elongation growth. Changes in cytoplasmic and wall bound peroxidase activities were studied using guaiacol as a hydrogen donor. Peroxidase activity was higher in both mercury and chromium treated seedlings as compared to distilled water control; they showed a clear concentration effect. Peroxidase activity showed inverse relation with growth i.e. distilled water treated seedlings had maximum growth and minimum activity while higher concentration of heavy metal treated seedlings had minimum growth and maximum activity. Chlorophyll content was also decreased by mercury. The role of peroxidase activity in defense mechanism in response to heavy metal toxicity is discussed.     

Arbuscular mycorrhizal fungi enhance root cadmium and copper accumulation in the roots of the salt marsh plant Aster tripolium L.

It is known that vegetation plays an important role in the retention of heavy metals in salt marshes by taking up and accumulating the metals. In this study, we investigated whether arbuscular mycorrhizal fungi (AMF) increase Cd and Cu uptake and accumulation in the root system of the salt marsh species Aster tripolium L., and whether indigenous AMF isolated from polluted salt marshes have higher capacity to resist and alleviate metal stress in A. tripolium than isolates of the same species originated from non-polluted sites. Plants inoculated with Glomus geosporum, either isolated from a polluted salt marsh site (PL isolate) or from a non-polluted site (NP isolate), and non-mycorrhizal (NM) plants were compared in a pot experiment at four different Cd and Cu concentrations. Cd had no effect in root colonization, whereas high concentrations of Cu decreased colonization level in plants inoculated with the NP isolate. AM colonization did not increase plant dry weight or P concentration but influenced root Cd and Cu concentrations. Inoculation with PL and NP isolates enhanced root Cd and Cu concentrations, especially at highest metal addition levels, as compared to NM plants, without increasing shoot Cd and Cu concentrations. There was no evidence of intraspecific variation in the effects between AMF isolated from polluted and non-polluted sites, since there were no differences between plants inoculated with PL or NP isolate in any of the tested plant variables. The results of this study showed that AMF enhance metal accumulation in the root system of A. tripolium, suggesting a contribution of AMF to the sink of metals within vegetation in the salt marshes.     

海水胁迫对苦荬菜幼苗生长及生理特性的影响

抗盐耐海水植物的种植是有效利用和开发滩涂资源的措施之一。采用温室砂培方式, 研究了不同稀释配比的海水处理8天对苦荬菜（Lactuca indica）幼苗生物量、根冠比、叶绿素含量、离子含量、可溶性蛋白和可溶性糖含量的影响。结果表明： 苦荬菜幼苗地上部受海水胁迫较为显著, 而根在海水浓度小于30%时与对照相比没有显著差异; 根冠比随着海水浓度的增加而不断提高; 在10%和20%海水浓度处理下, 叶绿素含量与对照相比差异不显著, 但随着海水浓度的进一步增加,叶绿素含量显著下降; 在10%海水浓度处理下, 苦荬菜地上部分及根部的K＋含量与对照相比差异不显著, 而海水浓度高于10%时, 随着海水浓度的增加地上部和根部的K＋含量均逐渐降低; 海水处理下, 苦荬菜体内Na＋和Cl–含量逐渐增加; 地上部可溶性糖含量逐渐增加, 而可溶性蛋白含量先升后降。海水胁迫下, 苦荬菜幼苗维持一定的K＋选择性吸收是其一定程度上盐适应的重要原因。同时, 积累的可溶性糖和可溶性蛋白是苦荬菜幼苗在盐胁迫下的重要渗透调节物质, 可作为其抗盐性的生理参数。     

Stimulation of cytokinins and chlorophyll synthesis in cucumber cotyledons by triadimefon

Triadimefon [1-(4-chlorophenoxy)-3,3-dimethyl-1-(1,2,4-triazol-1-yl)-2-butanone] changes the morphology and partitioning of dry matter in cucumber ( Cucumis sativus L. cv. National Pickling) seedlings. The dry weights, potassium and cytokinin levels in the cotyledons and roots of the treated seedlings were higher, whereas the hypocotyl weights were lower than the controls. When etiolated intact seedlings or cotyledons excised from triadimefon-pretreated dark-grown seedlings were exposed to light, chlorophyll synthesis in the pretreated cotyledons was stimulated. Triadimefon does not have cytokinin-like activity in the cucumber cotyledon greening bioassay, but appears to induce the plants to produce more cytokinims, probably by stimulating root growth. Hence it is proposed that the stimulation of chlorophyll production by triadimefon in cucumber cotyledons is mediated by maintaining high levels of potassium and cytokinins in the cotyledons.     

Effects of far-red light on the growth,mycorrhizas and mineral nutrition of Scots pine seedlings

The effects of supplementary far-red sidelight on the formation of mycorrhizas and on the accumulation and allocation of dry weight and mineral nutrients were studied in Scots pine (Pinus sylvestris L.) seedlings. Starting one week after germination the seedlings were subjected to two different light quality regimes: control and simulated sparse-canopy conditions (FR+). In the FR+ regime, light reflected by neighbouring plants was simulated by means of supplementary far-red light sources, which reduced the horizontal red/far-red photon ratio (R:FR) without affecting PAR. Seedlings were harvested after three months of treatment. FR+ increased stem height and decreased the total dry weight of seedlings. Dry weight allocation to needles was not affected, whereas dry weight allocation to roots was reduced and that to stems was increased in FR+ treated seedlings. The total number of short root tips and developing mycorrhizas per seedling were lower in FR+ than in control plants. Most short roots were developing mycorrhizas, while non-mycorrhizal short roots and mycorrhizas with mantle or external mycelium were very scarce. Changes in the allocation of nutrients in general followed the changes in dry weight allocation, and changes in nutrient content followed those in total dry weight. However, mismatches among these changes resulted in significant changes in nutrient concentrations in some organs: the concentrations of nitrogen and potassium in needles and the concentration of nitrogen in stems were higher in FR+ than in control seedlings. Changes in biomass and nutrient allocation under low R:FR may promote rapid height growth during early development in stands of Scots pine seedlings, but concomitant reductions in growth of the root system and mycorrhizas may negatively affect tree performance over the long term.     

Assessment of paraquat genotoxicity on barley (Hordeum vulgare L.) seedlings using molecular and biochemical parameters

The effects of exposure of barley seedlings to different concentration (10^?6 to 10^?3 mol/l) of paraquat on seed germination, root length, antioxidant enzyme activities and randomly amplified polymorphic DNA (RAPD) profiles were investigated. The results revealed that malondialdehyde content significantly increased by exposing paraquat in a concentration-dependent manner (p < 0.05). A significant increase in peroxidase and catalase activities in seedlings was observed with increased concentration of paraquat, and then decreased when the value reached 10^?3 mol/l, whereas the activities of superoxide dismutase gradually increased with increasing paraquat concentration. Germination and root elongation also decreased with the increase of paraquat concentration. On the other hand, alterations of DNA in barley seedlings were detected using RAPD technique. The changes occurring in RAPD profiles of seedlings following paraquat treatment included loss of bands found in DNA of control seedlings and appearance of new bands. The results of this study showed that paraquat induced DNA damage in a dose-dependent manner and the root cells of barley showed a defense against paraquat-induced oxidative stress by enhancing their antioxidant activities.