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1.
Barley plants (Hordeum vulgare L. cv. Obzor) were grown as a water culture in a climatic room. One part of them was subjected
to a long-term Cd 2+ stress - 12 d with 5.4×10 −5 M Cd. The Cd 2+ stress inhibited formation of the photosynthetic apparatus and its capacity for 14C photoassimilation, decreased the content of soluble proteins, increased the dark respiration rate and the free amino acids
content, disturbed plant water relations, as well as the distribution of 14C within primary photoproducts of the treated barley plants.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
2.
Industry residues, phosphate fertilisers and wastewater as a source of irrigation have considerably increased levels of heavy metals in the soil, mainly cadmium (Cd 2+). To test the effects of a calcium (Ca 2+) treatment on Cd 2+ accumulation and plant tolerance to this heavy metal, plants of two citrus genotypes, Cleopatra mandarin (CM) and Carrizo citrange (CC), were watered with increasing concentrations of Cd 2+, and phytochelatin (PC) and glutathione (GSH) content were measured. Both genotypes were able to synthesise PCs in response to heavy metal intoxication, although CM seems to be a better Cd 2+ excluder than CC. However, data indicate that CC plants had a higher capacity for regenerating GSH than CM plants. In this context, the effects of Ca 2+ treatment on Cd 2+ accumulation, plant survival and PC, GSH and oxidised glutathione (GSSG) content were assessed. Data indicate that treatment with Ca 2+ had two positive effects on citrus physiology: it reduced Cd +2 uptake into roots and also increased GSH content (even in the absence of Cd 2+). Overall, the data indicate that although Cd 2+ exclusion is a powerful mechanism to avoid heavy metal build‐up into photosynthetic organs, the capacity to maintain optimum GSH levels to feed PC biosynthesis could also be an important factor in stress tolerance. 相似文献
3.
重金属镉(Cd)的毒害效应与其由土壤向植物地上部分运输有关,揭示Cd~(2+)转运途径及其调控机制可为提高植物抗镉性以及镉污染的植物修复提供依据。对Cd~(2+)在植物体内的转运途径,特别是限制Cd~(2+)移动的细胞结构和分子调控机制研究进展进行了回顾。Cd~(2+)通过共质体和质外体途径穿过根部皮层进入木质部的过程中,大部分在皮层细胞间沉积,少部分抵达中柱后转移到地上部分。为了免受Cd~(2+)的危害,植物体产生了多种限制Cd~(2+)吸收和转移的生理生化机制:1)环绕在内皮层径向壁和横向壁上的凯氏带阻止Cd~(2+)以质外体途径进入木质部;2)螯合剂与进入根的Cd~(2+)螯合形成稳定化合物并区隔在液泡中;3)通过H+/Cd~(2+)离子通道等将Cd~(2+)逆向转运出根部。植物共质体和质外体途径转运重金属镉的能力以及两条途径的串扰尚待进一步明晰和阐明。 相似文献
4.
Cadmium toxicity has been extensively studied in plants, however its biochemical mechanism of action has not yet been well
established. To fulfil this objective, four-weeks-old soybean nodulated plants were treated with 200 μM Cd 2+ for 48 h. δ-aminolevulinic acid dehydratase (ALA-D, E.C. 4.2.1.24) activity and protein expression, as well as δ-aminolevulinic
acid (ALA) and porphobilinogen (PBG) concentrations were determined in nodules, roots and leaves. In vitro experiments carried
out in leaves were performed using leaf discs to evaluate the oxidant and antioxidant properties of ALA and S-adenosyl- l-methinone (SAM), respectively. Oxidative stress parameters such as thiobarbituric acid reactive substances (TBARS) and GSH
levels as well as superoxide dismutase (SOD, E.C. 1.15.1.1), and guaiacol peroxidase (GPOX, E.C. 1.11.1.7) were also determined.
Cadmium treatment caused 100% inhibition of ALA-D activity in roots and leaves, and 72% inhibition in nodules whereas protein
expression remained unaltered in the three studied tissues. Plants accumulated ALA in nodules (46%), roots (2.5-fold) and
leaves (104%), respect to controls. From in vitro experiments using leaf discs, exposed to ALA or Cd 2+, it was found that TBARS levels were enhanced, while GSH content and SOD and GPOX activities and expressions were diminished.
The protective role of SAM against oxidative stress generated by Cd 2+ and ALA was also demonstrated. Data presented in this paper let us to suggest that accumulation of ALA in nodules, roots
and leaves of soybean plants due to treatment with Cd 2+ is highly responsible for oxidative stress generation in these tissues. 相似文献
5.
Barley (Hordeum vulgare L., cv. Hemus) plants were grown in nutrient solution with or without 54 μM Cd 2+ for 12 d. A treatment with Cd 2+ inhibited the growth of young barley plants. The main factor limiting plant growth was net assimilation rate, due to decreased
photosynthetic rate and accelerated dark respiration rate. One of the reasons for the reduced photosynthetic rate was the
lower chlorophyll and carotenoid content. Cd 2+ decreased water potential and transpiration rate, but relative water content in leaves of the treated plants was not significantly
changed.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
7.
Barley ( Hordeum vulgare L.) plants at the three-leaf stage were water-stressed by flooding the rooting medium with polyethylene glycol 6000 with an osmotic potential of −19 bars, or by withholding water. While leaf water potential fell and leaf kill progressed, the betaine (trimethylglycine) content of the second leaf blade rose from about 0.4 micromole to about 1.5 micromoles in 4 days. The time course of betaine accumulation resembled that of proline accumulation. Choline levels in unstressed second leaf blades were low (<0.1 micromole per blade) and remained low during water stress. Upon relief of stress, betaine-like proline—remained at a high concentration in drought-killed leaf zones, but betaine did not disappear as rapidly as proline from viable leaf tissue during recovery. When [methyl-14C]choline was applied to second leaf blades of intact plants in the growth chamber, water-stressed plants metabolized 5 to 10 times more 14C label to betaine than control plants during 22 hours. When infiltrated with tracer quantities of [14C]formate and incubated for various times in darkness or light, segments cut from water-stressed leaf blades incorporated about 2- to 10-fold more 14C into betaine than did segments from unstressed leaves. In segments from stressed leaves incubated with [14C]formate for about 18 hours in darkness, betaine was always the principal 14C-labeled soluble metabolite. This 14C label was located exclusively in the N-methyl groups of betaine, demonstrating that reducing equivalents were available in stressed leaves for the reductive steps of methyl group biosynthesis from formate. Incorporation of 14C from formate into choline was also increased in stressed leaf tissue, but choline was not a major product formed from [14C]formate. These results are consistent with a net de novo synthesis of betaine from 1- and 2-carbon precursors during water stress, and indicate that the betaine so accumulated may be a metabolically inert end product. 相似文献
8.
Effect of Cd 2+ toxicity and heat stress in sensitive rice cv. DR-92 and tolerant rice cv. Bh-1 grown in North East region of India were studied in sand cultures. Increasing levels of 0–500 μM Cd 2+ alone and/or heat stress showed increased activities of superoxide dismutase, guaiacol peroxidase, ascorbate peroxidase and
glutathione reductase enzymes which were associated with induced oxidative stress and altered enzyme activities. The values
for SOD and POD activities were always more in cv. DR-92 whereas CAT and GR activities were higher in cv. Bh-1 in roots and shoots under Cd 2+ or heat stress alone in sensitive cv. DR-92. Upon imposition of a combination of Cd 2+ + heat the activities of SOD and POD decreased significantly in root/shoot of both the sensitive and tolerant rice varieties.
A nine fold increase in GR activity under combination of heat + 100 μM Cd 2+ stress in shoots of cv. Bh-1 at day 15 was noted when compared to controls. The dual stress combination of Cd 2+ + heat did not alter catalase activity in vivo in both the rice varieties. Results suggest a time-specific and varietal distribution
of the antioxidant enzymes in rice plants subjected to Cd 2+ and/or heat stress. Tolerant cv. Bh-1 has better survival to combined stressors like Cd 2+ and heat than sensitive rice cv. DR-92 and heat stress when given in combination with Cd 2+ toxicity seem to mitigate the effect of Cd 2+ stress alone in rice. The study indicates individual Cd 2+ toxicity and heat stress and a combination of the two stresses to have separate implications on antioxidative defense mechanism
in rice plants. Among enzymes of the defense apparatus ascorbate peroxidase and glutathione reductase appear to serve as an
important component for better survival of rice plants under combination of Cd 2+ + heat stress. 相似文献
9.
Introduction – Since the mechanism of Cd 2+ stress for plants is not clear, an in vivo method to monitor Cd 2+ stress for plants is necessary. However, oxidative burst (OB) is a signal messenger in the process of Cd 2+ stress for plants. Objective – To establish an electrochemical method with poly‐ o‐phenylenediamine and Pt microparticle modified Pt electrode (POPD–Pt‐MP–Pt) as a microbiosensor for the in vivo detection of oxidative burst induced by Cd 2+ stress in oilseed rape ( Brassica napus L.). Methodology – The optimal fabrication of POPD–Pt‐MP–Pt biosensor was achieved. Electrochemical signal was collected by amperometry. Results – After oilseed rape was exposed to 84.9 mM CdCl 2 stress, three oxidative bursts were observed in oilseed rape by amperometry at 3.3 h, 8.4 h and 13.2 h, respectively. However, there was no obvious signal observed in the controlled assay. Conclusion – This contribution presents the in vivo monitoring of the OB process induced by Cd 2+ stress in oilseed rape by POPD–Pt‐MP–Pt microbiosensor in real‐time. The novel electrochemical microbiosensor not only facilitates the real‐time study in plant self‐defence response to the adverse environment such as Cd 2+ stress, but also provides an effective tool for probing the self‐defence mechanism in plants. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
10.
Heavy metal pollution has become one of the most serious environmental problems today. To develop a more efficient plant to clean up heavy metal contaminated soils, a γ‐glutamylcysteine synthetase (GCS) cDNA, named PaGCS, was isolated by PCR from Phragmites australis. The PaGCS sequence was transformed via agroinfection into the heavy metal intolerant grass Agrostis palustris. Five confirmed transgenic A. palustris plants expressing PaGCS were compared with the wild‐type line for growth and Cd 2+ accumulation, as well as for the expression of a number of phytochelatin synthesis and stress‐responsive enzymes when challenged with Cd 2+ stress. GCS and phytochelatin synthase (PCS) were up‐regulated in the transgenic lines. All the transgenic lines accumulated more Cd 2+ and phytochelatins (PCs) than the wild‐type line, and three of the five lines grew more effectively than the wild‐type after either five or 21 d of Cd 2+ stress. Variation among the transgenics was observed for the distribution of Cd 2+ in the root, shoot and leaf. The malondialdehyde content of all the transgenic lines was lower than that of the wild type under Cd 2+ treatment, while the activity of both superoxide dismutase and peroxidase present in the transgenic lines increased markedly 24 h after Cd 2+ stress, and then rapidly declined. 相似文献
11.
Excess cadmium (Cd 2+) in the soil environment is taken up by plants and can cause phytotoxicity. Elevated temperatures also lead to deleterious effects on plants. Plants are very often exposed to a combination of stresses rather than a single stress. The effect of Cd 2+ and heat stress (HS) on the growth, root ultrastructure, lipid peroxidation (MDA), hydrogen peroxide accumulation and the activities of antioxidant enzymes peroxidase (POD), catalase (CAT) and ascorbate peroxidase (APX) of rice roots from sensitive cv. DR-92 and tolerant cv. Bh-1 were investigated at 10 and 20 day of growth under controlled conditions. At day 10 under all Cd 2+ treatments, the Cd 2+ content between the two rice cultivars were almost similar. Application of 500 μM Cd 2+ significantly increased metal concentrations at day 20 in the roots of rice seedlings resulting in a maximum accumulation of 44.25 μg Cd 2+ g -1 dry wt in cv. DR-92 and 30 μg Cd 2+ g -1 dry wt in cv. Bh-1 with a ~25 % decline in Relative Growth Index (RGI) in cv. DR-92. TEM studies revealed slight disorganization with cell wall ingrowths in root tissues from cv. DR-92 grown in 100 μM Cd 2+ + HS. Uptake and accumulation of Cd 2+ increased upon heat treatment in parenchyma, vacuoles and vascular cylinder of root tissues. Peroxidase primarily located in cell walls, the intensity being higher in sensitive cv. DR-92. Under Cd 2+ stress alone, plants of sensitive cv. DR-92 significantly increased the H 2O 2 and MDA levels together with increased activities of the enzymes POD, CAT and APX at day 10 but remained almost stable at day 20. A strong increase in MDA levels was noted at day 20 in tolerant cv. Bh-1. Cd 2+ + HS treatments in tolerant cv.Bh-1 led to a decreased H 2O 2 and MDA levels and decreased activities of the enzymes POD, CAT and APX. Results suggest stimulation of root antioxidant system under combination of two stresses and that heat stress seem to have a direct protective role by mitigating the effect of mild Cd 2+ toxicity largely by enhanced Cd 2+-MT formation contributing thereby towards the management of Cd 2+ toxicity at cellular level that confers Cd 2+ tolerance to rice cv. Bh-1. 相似文献
12.
Abstract Poplar plants were exposed during 61 days to a soil added with heavy metals so as to contain 300 mg Zn 2+.kg ?1 soil dry weight (SDW) (Zinc) or 50 mg Cd 2+.kg ?1 SDW (Cadmium). The Cd treatment induced a delayed growth of poplar, whereas Zn induced no change in physiological parameters. Both treatments resulted in a significant metal accumulation in plants. Zn 2+ and Cd 2+ exhibited contrasting distribution within tissues, indicating dissimilar handling by the plant. The main difference was the efficient compartmentalisation of Zn 2+ in specific organ parts: old leaves and bark, while Cd 2+ did not exhibit such a compartmentalisation. Results were also compared with a previous work where plants were exposed to 360 mg Cd 2+.kg ?1 SDW. 相似文献
13.
This study was designed to examine whether exogenous Ca 2+ would improve nitrogen nutrition, water status and growth of high temperature (HT)-stressed wheat ( Triticum aestivum) seedlings. Wheat plants were exposed to 35/30 and 25/20°C as temperature control. Some of HT-stressed plants were simultaneously
treated with 4 mM Ca 2+. External Ca 2+ could obviously improve growth of HT-exposed wheat seedlings indicated by the biomass. Compared with Ca 2+-untreated plants, total nitrogen content showed a significant increase in Ca 2+-treated plants under HT stress, this primarily resulted from enhanced nitrate reductase activity and depressed loss of ammonium
through photorespiration. External Ca 2+ application could also increase leaf relative water content and alleviate osmotic stress via increased K + ion and water-soluble carbohydrates in HT-stressed plants. Whereas free proline content showed remarkable decline in Ca 2+-treated plants at HT stress. 相似文献
15.
该研究以Cu~(2+)、Zn~(2+)、Cd~(2+)单一胁迫为对照,探讨不同浓度的Cu~(2+)、Zn~(2+)、Cd~(2+)复合胁迫对麻疯树幼苗生理生化指标的影响。结果表明:随着Cu~(2+)、Zn~(2+)、Cd~(2+)浓度的增加,麻疯树幼苗叶片中的蛋白质(Pro)、丙二醛(MDA)含量均逐渐增加,其叶片叶绿素含量随着Zn~(2+)胁迫浓度的增加呈现出先降后升的趋势,在中等浓度(100 mg·L-1)的Zn~(2+)胁迫时含量最低、随着Cu~(2+)胁迫浓度的增加叶绿素含量先升高后降低,在Cu~(2+)浓度为200 mg·L-1时含量最高,达到1 200 mg·g-1FW; Cd~(2+)胁迫对叶绿素含量和根系活力无明显影响。根系活力在Zn~(2+)浓度为100 mg·L~(-1)时最强,随着Cu~(2+)浓度的增加而减弱。低浓度的Cu~(2+)、Zn~(2+)、Cd~(2+)对过氧化物酶活性和可溶性糖含量都具有促进作用。Cu~(2+)、Zn~(2+)、Cd~(2+)复合胁迫时对可溶性蛋白、叶绿素和丙二醛含量均无明显影响,随着复合胁迫时浓度的增加,可溶性糖含量和根系活力先增后减。这表明麻疯树对三种重金属的胁迫具有一定的抗性,过高浓度的胁迫会影响麻疯树幼苗生理生化的一些指标,但是麻疯树可以通过自身的防御系统使伤害降到最小。此外,重金属复合胁迫可以在一定程度上减轻单一胁迫对麻疯树幼苗造成的毒害作用。 相似文献
16.
Effects of Cd 2+ toxicity on the photochemistry of primary leaves at two different growth stages of runner bean plants were taken into consideration
to study whether Cd 2+ can use Ca 2+ channels to get into chloroplasts. Different concentrations of Cd 2+, ionophore A 23187 and Ca 2+ were vacuum infiltrated into leaf discs. Toxicity of Cd 2+ at the donor side of PSII depending on the metal concentration and age of the plants was confirmed. Application of ionophore
caused an increase in the sensitivity of the PSII donor side to low Cd 2+ concentrations. Additional supply of Ca 2+ in the infiltration medium abolished toxic effect of Cd 2+ on photochemical activity, except for older plants, where it was not observed for the highest Cd 2+ concentration. In our opinion it is possible that Cd 2+ penetrates into chloroplasts via Ca 2+ channels. Age-dependent Ca 2+ content in the primary leaves seems to be a very important factor protecting photochemical activity from the toxic action
of Cd 2+. 相似文献
17.
Trace element contamination of lands is a serious environmental problem that limits yield and threatens human health. To study the combined effect of high salinity and toxic levels of trace elements on halophytes, the performance of two marsh species, Atriplex halimus and Suaeda fruticosa, grown for 1 month with an irrigation solution supplemented with 200 mM NaCl and 400 μM Cd 2+ or 400 μM Cu 2+ was evaluated. The effect of the combined stress conditions on hormone signaling was also assessed. Biomass production and chlorophyll content decreased under Cd 2+ stress in both species, whereas Cu 2+ had a lower impact on plant performance. The different plant sensibilities to the two trace elements assayed indicate that each metal has a different effect on plants. Furthermore, the deleterious effect of metal toxicity was alleviated when NaCl was added to the irrigation solution, demonstrating that NaCl improves plant performance and tolerance of halophytic species to cope with trace element intoxication. Results show that both species accumulated important quantities of Cd 2+ and Cu 2+ in roots (Cd 2+: 2,690–3,130 μg g ?1 DW and Cu 2+: 2,070–2,770 μg g ?1 DW); this finding allows us to classify these species among the hyperaccumulator plants. Cd 2+ and Cu 2+ differently affected endogenous phytohormone contents in both species. Data suggest an essential involvement of roots on the regulation of tolerance to trace elements. Therefore, indole-3-acetic acid levels increased in roots of both species irrigated with high levels of Cd 2+, which suggests that the auxin may stimulate root promotion and growth under these stress conditions. Other compounds, classically considered as “stress hormones” showed very different patterns of accumulation. Whereas, salicylic acid (SA) levels in roots and leaves increased in response to Cd 2+, root contents of jasmonic acid (JA), and abscisic acid (ABA) decreased. In leaves, the rambling pattern of accumulation observed for JA and ABA suggested the lack of a specific role in regulation against trace element toxicity. Together, data suggest that SA could act as a specific signal that detects trace element toxicity, whereas JA and ABA promote general responses against abiotic stress. 相似文献
18.
河流、湖泊等水生环境中普遍存在的重金属污染破坏水生生态系统并间接威胁人类健康。为探究重金属胁迫下水生昆虫花翅摇蚊( Chironomus kiiensis)生态毒理,测定了重金属Cd 2+和Pb 2+胁迫对花翅摇蚊化蛹率和羽化率的影响,检测了摇蚊的口器致畸与富集效应。研究结果表明,Cd 2+和Pb 2+影响摇蚊幼虫化蛹和羽化过程,单一重金属离子处理14 d Pb 2+处理组的化蛹率和羽化率分别为22.22%和8.89%,低于Cd 2+的化蛹率(25.56%)和羽化率(11.11%),表现出更强的抑制效应。混合离子1:2和2:1配比处理组化蛹率和羽化率均为11.11%和4.44%,显著低于单一重金属离子胁迫下的化蛹率和羽化率。单一重金属离子及混合离子处理均能导致花翅摇蚊幼虫口器致畸,表现为上颚前齿断裂,中齿和基齿磨损、缺失,下唇板齿部不规则,下唇板边缘齿与中央齿磨损、断裂、增生、缺失。不同重金属离子处理下幼虫口器致畸率不同,并与暴露时间呈正相关,其中1:2配比处理14 d致畸率达到40.61%。重金属离子在摇蚊幼虫体内产生生物富集效应,单一重金属离子处理下的Pb 2+富集含量7 d至14 d由11.46 mg/kg上升至31.32 mg/kg,不同配比混合离子处理下Pb 2+富集含量均呈增加趋势,其中1:2配比处理组由15.48 mg/kg上升至42.50 mg/kg,而Cd 2+在单一重金属与1:1混合离子处理组7 d至14 d的富集含量无显著性变化,2:1配比处理组由14.20 mg/kg下降至9.52 mg/kg,1:2配比由5.85 mg/kg上升至20.99 mg/kg。这些研究结果表明Cd 2+和Pb 2+胁迫影响花翅摇蚊幼虫生长发育且口器出现畸型,与重金属在幼虫体内的富集密切相关,为研究重金属对水生生态系统多重效应提供了理论依据。 相似文献
19.
Changes in the content of reactive oxygen species (ROS) and activity of the antioxidant system were measured in leaves of
Arabidopsis thaliana (L.) Heynh exposed to Cd 2+. Mature plants growing in the nutrient solution were treated with Cd 2+ at different concentrations (0, 5, 25, 50, 100 μM). An increase of
content in leaves was observed at 5, 25 and 50 μM Cd 2+. A strong accumulation of H 2O 2 was found only at the lowest Cd 2+ concentration. The content of OH *. was high at 50 and 100 μM Cd 2+. Superoxide dismutase (SOD) activity was always higher in Cd 2+-treated plants than in control. Catalase (CAT) activity decreased with increasing Cd 2+ concentration in the nutrient solution. Guaiacol peroxidase (POX) activity was particularly high at the lowest and highest
Cd 2+ concentrations and ascorbate peroxidase (APX) activity additionally at 50 μM Cd 2+. Enhanced activity of monodehydroascorbate reductase (MDHAR) and strong reduction in ascorbate (AA) content were observed
at 25 μM Cd 2+. Glutathione reductase (GR) activity was always higher than in control but decreased as Cd 2+ concentration increased. However, it was accompanied by gradual content increase of SH-groups.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
20.
The effects of Cd 2+, Cr 3+ and Zn 2+ on the microbial activity of water and sediment samples from a contaminated stream were studied. The maximum [ 14C]glucose uptake (V max) and the mineralization ( 14CO 2) rates were determined. A 10% reduction in V max was obtained at lower metal concentrations in water samples than in sediment ones. Moreover, a 10% decrease in 14CO 2 was observed at significantly minor metal levels, so 14CO 2 was more sensitive to evaluated heavy metal pollution. On the basis of MICs obtained for both communities, they were more sensitive to Cd 2+ than to Cr 3+ and Zn 2+. Zinc was less inhibitory to V max and 14CO 2 rates; Cr 3+ showed an intermediate toxicity, and Cd 2+ was 10–100 times more inhibitory than the other metals. 相似文献
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