Effects of aluminum and cadmium toxicity on growth and antioxidant enzyme activities of two barley genotypes with different Al resistance

A hydroponic experiment was carried out to study genotypic differences in effect of Al and Cd on growth and antioxidant enzyme activities by using 2 two-row winter barley genotypes (Hordeum vulgare L.) with different Al resistance, the relatively resistant Gebeina and the sensitive Shang 70–119. The seedling growth, presented as shoot height, root length and dry weight of root and shoot, and tillers per plant were inhibited by all stress treatments, including low pH, 100 M Al (pH 4.0) and 1.0 M Cd+100 M Al (pH 4.0), while 1.0 M Cd showed a slight stimulation of growth. The inhibition was more severe in 1.0 M Cd +100 M Al (pH 4.0) than in 100 M Al (pH 4.0), indicating that the effect of Cd and Al is synergistic. Al-sensitive genotype Shang 70–119 was more inhibited than Al-resistant genotype Gebeina. Proline concentration in leaves was significantly increased when plants were exposed to all stress treatments, being more pronounced in Shang 70–119 than in Gebeina. A highly significant increase in malonaldehyde (MDA) concentration, and a stimulation of superoxide dismutase (SOD) and peroxidase (POD) activities were recorded in the plants subjected to low pH, 100 M Al (pH 4.0) and 1.0 M Cd +100 M Al(pH 4.0) treatments, and the extent of the increase varied greatly depending on concentration and time of exposure. Shang 70–119 had a higher MDA concentration, and less increase in SOD activity when first exposed than Gebeina had.     

Accumulation of Microsomal Polypeptides in Barley Roots during Aluminium Stress

Accumulation of two peripheral membrane polypeptides (20 and 28 kDa) in roots of Al-sensitive (cv. Alfor) and Al-resistant (cv. Bavaria) barley cultivars were analysed during Al stress. Both cultivars were subjected to Al concentration ranging from 0 to 150 µM for 24, 48, 72 and 96 h. Accumulation of both polypeptides was determined 24 h after exposure of plants to Al and content of both polypeptides showed only small depedence upon Al concentration and duration of Al treatment. Although, based on root growth test, Bavaria showed significantly greater resistance to Al than Alfor, analysis of 20 and 28 kDa polypeptide pattern has not revealed significant difference between the two cultivars. However, accumulation of 20 and 28 kDa polypeptides in Alfor was selectively induced by Al treatment because different pH of the root media (pH 3.5 to 6.5) or application of other metals (Cu, Co, or Cd) failed to induce these two bands. On the other hand, accumulation of these polypeptides in Bavaria was induced not only by Al, but also by Cd and in a lesser extent by Co treatment.     

Iron nutrition affects cadmium accumulation and toxicity in rice plants

The effect of iron (Fe) nutrition on cadmium (Cd) toxicity and accumulation in rice plants was studied using a hydroponic system. The inhibitory effect of Cd on plant growth and chlorophyll content (SPAD value) was dependent on Fe level and the genotype. Malondialdehyde (MDA) content in leaves and roots was not much affected by an increased Cd stress at 0.171 mg l⁻¹ Fe, but it showed a rapid increase when the plants were exposed to moderate (1.89 mg l⁻¹) and high (16.8 mg l⁻¹) Fe levels. High Fe nutrition caused a marked reduction in Cd content in both leaves and roots. Fe content in plants was lower at high Cd (5.0 μM) stress than at low Cd (<1.0 μM) stress. Cd stress increased both superoxide dismutase (SOD) and peroxidase (POD) activities at low and moderate Fe levels. However, with high Fe level, it increased the POD activity, but reduced the SOD activity. Our results substantiate the hypothesis that cell membrane-bound iron transporter (carrier) involved in high-affinity iron transport systems can also transport Cd, and both these ions may compete for this common carrier. The study further showed that there were significant correlations between MDA and Fe contents in leaves and roots of rice plants. It is suggested that the occurrence of oxidative stress in plants exposed to Cd stress is mediated by Fe nutrition. The present results also show that Cd stress affects the uptake of Cu and Zn.     

外源脱落酸对小麦幼苗抗镉胁迫能力的影响

以小麦(Triticum aestivum L.)为试材,采用水培法研究了100mg/L镉(Cd2+)胁迫条件下施用外源脱落酸(ABA)对小麦幼苗生长及某些生理生化指标的影响。结果表明:(1)100mg/L Cd2+胁迫下,小麦叶片膜脂过氧化产物丙二醛(MDA)含量显著提高,植株生长受到抑制;(2)外源ABA能够明显提高Cd2+胁迫小麦幼苗的根系活力,增加其叶片SOD、CAT和POD活性,促进其脯氨酸积累,降低MDA的含量,并以5.0μmol/L ABA的效果最明显;(3)1.0～5.0μmol/L外源ABA不同程度地缓解Cd2+胁迫对小麦幼苗生长的抑制作用,且5.0μmol/L时效果最明显,其株高、根长、总干重分别比单一Cd2+胁迫处理显著提高6.73%、149%和10.52%,而10.0μmol/LABA反而加重了Cd2+对小麦幼苗生长的伤害。因此,适宜浓度的外源ABA能够通过增加体内保护酶活性和脯氨酸含量来缓解Cd2+胁迫对小麦幼苗生长的抑制作用,增强小麦幼苗的抗Cd2+胁迫能力,并以5.0μmol/L ABA处理效果最好。     

外源钙对镉胁迫下南美蟛蜞菊毛状根生长、抗氧化酶活性和镉吸收的缓解效应

为了探讨外源钙对重金属镉(Cd)缓解南美蟛蜞菊Wedelia trilobata毛状根毒害的生理机理,采用溶液培养法研究了重金属Cd单独及其与Ca组合对南美蟛蜞菊毛状根生长、抗氧化酶超氧化物岐化酶(SOD)和过氧化物酶(POD)活性及对Cd2+吸收的影响。结果表明,Cd≤50μmol/L时促进毛状根生长;高于100μmol/LCd则抑制其生长,使其侧根短小,根尖变褐或变黑。与对照相比,不同浓度Cd培养的毛状根POD活性、SOD活性和MDA含量都比对照明显提高,但高于100μmol/L Cd培养的毛状根可溶性蛋白含量均比对照降低。与仅添加200μmol/L或300μmol/L Cd的毛状根相比,Cd和10~30 mmol/L Ca组合培养可促进毛状根生长,使其主、侧根变粗;提高其可溶性蛋白含量;降低其MDA含量、POD活性及SOD活性。原子吸收分光光度法测定结果表明,南美蟛蜞菊毛状根能吸收和吸附重金属Cd2+,当Cd2+浓度为100μmol/L时毛状根对Cd2+的吸收量最大,而Cd2+浓度为300μmol/L时毛状根对Cd2+的吸附量最大。外源加入10~30 mmol/L Ca2+可显著减少毛状根对Cd2+的吸收和吸附,并可调节其抗氧化酶活性,降低其膜脂过氧化水平而解除重金属镉对毛状根生长的抑制或毒害。     

Stress Responses of Zea mays to Cadmium and Mercury

A hydroponic experiment was carried out to characterize the oxidative stress responses of maize seedlings (Zea mays L. cv. Dekalb DK604) to cadmium (Cd) and mercury (Hg). Plants were grown hydroponically for 7 days in a nutrient solution supplemented with several concentrations of Cd and Hg: 0.0 (control), 6 or 30 μM. Growth was inhibited by both metals. The effect was more severe in plants exposed to Hg. Oxidative stress was caused by the exposure to the metals, as quantified by malondialdehyde and carbonyl accumulation, by-products of lipid peroxidation and protein oxidation, respectively. The activity of ascorbate peroxidase (APX) and superoxide dismutase (SOD), enzymes involved in the scavenging of reactive oxygen species, were measured upon metal treatment. We found an activation of a cytosolic APX isoform, as identified by using a specific polyclonal antiserum. However, there were negligible changes in SOD activity. Analysis of thiol-peptides revealed that at 6 μM Cd a remarkable increase in root reduced glutathione (GSH) content occurred, and little effect on the relative content of oxidised glutathione (GSSG) was observed. However, at 30 μM Cd and in plants exposed to 6 and 30 μM of Hg, GSH root content either remained stable or decreased significantly, while the proportion of GSSG increased. Moreover, only Cd was able to induce accumulation of phytochelatins at both assayed concentrations. Apparently, Hg was more toxic than Cd, as inferred from the magnitude of the changes found in the physiological parameters tested.     

Response of antioxidant enzymes in rice (<Emphasis Type="Italic">Oryza sauva</Emphasis> L. cv. Dongjin) under mercury stress

We studied the effects of different concentrations of mercury (0.0 to 100 μM) on growth and photosynthetic efficiency in rice plants treated for 21 d. In addition, we investigated how this metal affected the malondialdehyde (MDA) content as well as the activity of five antioxidant enzymes — superoxide dismutase (SOD), ascorbate peroxidase (APX), glutathione reductase (GR), guaiacol peroxidase (POD), and catalase (CAT). Photosynthetic efficiency (Fμ/F_m) and seedling growth decreased as the concentration of Hg was increased in the growth media. Plants also responded to Hg-induced oxidative stress by changing the levels of their antioxidative enzymes. Enhanced lipid peroxidation was observed in both leaves and roots that had been exposed to oxidative stress, with leaves showing higher enzymatic activity. Both SOD and APX activities increased in treatments with up to 50 μM Hg, then decreased at higher concentrations. In the leaves, both CAT and POD activities increased gradually, with CAT levels decreasing at higher concentrations. In the roots, however, CAT activity remained unchanged while that of POD increased a bit more than did the control for concentrations of up to 10 μM Hg. At higher Hg levels, both CAT and POD activities decreased. GR activity increased in leaves exposed to no more than 0.25 μM Hg, then decreased gradually. In contrast, its activity was greatly inhibited in the roots. Based on these results, we suggest that when rice plants are exposed to different concentrations of mercury, their antioxidative enzymes become involved in defense mechanisms against the free radicals that are induced by this stress.     

The Effect of Salinity Pretreatment on Cd Accumulation and Cd-Induced Stress in <Emphasis Type="Italic">BADH</Emphasis><Emphasis Type="Italic">-</Emphasis>Transgenic and Nontransgenic Rice Seedlings

The influence of betaine aldehyde dehydrogenase (BADH) and salinity pretreatment on oxidative stress under cadmium (Cd) toxicity was investigated in rice cv. Xiushui 11 and its BADH-transgenic line Bxiushui 11. The results showed that plants previously treated with 4.25 and 8.5 mM NaCl, respectively, for 5 days each had higher Cd concentrations in both roots and shoots of the two rice genotypes compared with the controls. Malondialdehyde (MDA) content in both leaves and roots was increased by salinity pretreatment and was significantly lower in the salinity-pretreatment plants than in the controls when the plants were consequently exposed to Cd stress. Salinity pretreatment also increased proline content and the activities of superoxide dismutase (SOD) and peroxidase (POD) in both leaves and roots. It can be assumed that salinity pretreatment enhances the defensive ability of plants against oxidative stress through increasing activities of antioxidative enzymes. The BADH-transgenic line (Bxiushui 11) had lower Cd and MDA content, higher SOD and POD activities, and higher proline content than its wild type (Xiushui 11). The current results suggest that betaine, a product of BADH expression, improves the tolerance of rice plants to Cd stress through increasing the activities of antioxidative enzymes and osmoprotectant content.     

镉胁迫下大豆生长发育的生理生态特征

采用土壤盆栽试验方法,研究了不同浓度Cd2+胁迫对大豆整个生长发育周期的生长以及叶片叶绿素含量、超氧化物歧化酶(SOD)活性、过氧化物酶(POD)活性和丙二醛(MDA)含量的生理生态适应性变化过程。结果表明,(1)Cd2+胁迫对大豆整个生活周期的叶绿素含量、POD活性、SOD活性及MDA含量的影响都是极显著的(P0.01);(2)短时间、低浓度的Cd2+胁迫对大豆植株的生长发育有刺激效应,高浓度、长时间的Cd2+胁迫对大豆植株构成明显的抑制效应;大豆株高增长开始受到抑制的Cd2+浓度为1.00mg·kg-1,远低于大豆生物量的增长开始受抑制的Cd2+浓度(2.50mg·kg-1);(3)当Cd2+浓度超过一定水平时,大豆植株生物量和株高的抑制程度与外源Cd2+浓度呈极显著的正相关(P0.01),对土壤Cd2+污染程度具有指示作用,且大豆植株高度与其生物量相比,株高对Cd2+污染具有更好的指示作用;大豆幼苗期叶绿素含量对镉的敏感性高于开花结荚期和成熟期的敏感性;(4)大豆POD、SOD活性的增加,能在一定程度上减轻Cd2+胁迫引起的膜脂过氧化造成的伤害作用;在Cd2+达到2.50mg·kg-1水平时,植物保护性酶系统活性的提高已经不足以弥补因Cd2+胁迫对大豆植株造成的伤害;大豆幼苗期和花荚期叶片的POD活性对土壤Cd2+污染程度具有较好的指示作用,而大豆花荚期和成熟期叶片的SOD活性对土壤Cd2+污染程度具有较好的指示作用;在Cd2+胁迫下大豆MDA含量增加,表明细胞膜脂过氧化作用加强。     

镉对小麦幼苗脂质过氧化和保护酶活性的影响

小麦幼苗经镉胁迫后,随着镉浓度的增高,叶征和根系中的膜脂过氧化产物丙二醛（ＭＤＡ）的含量和过氧物酶（ＰＯＤ）活性明显升高,超氧物歧化酶（ＳＯＤ）活性也有所提高。叶片中ＭＤＡ积累量和ＳＯＤ活性都高于根,而ＰＯＤ活性则是根高于叶片。随幼苗生长时间延长,叶片和根中的ＭＤＡ积累量增加,而ＳＯＤ活性却降低。     

Silicon alleviates simulated acid rain stress of <Emphasis Type="BoldItalic">Oryza sativa</Emphasis> L. seedlings by adjusting physiology activity and mineral nutrients

Silicon (Si) has been a modulator in plants under abiotic stresses, such as acid rain. To understand how silicon made an effect on rice (Oryza sativa L.) exposed to simulated acid rain (SAR) stress, the growth, physiologic activity, and mineral nutrient content in leaves of rice were investigated. The results showed that combined treatments with Si (1.0, 2.0, or 4.0 mM) and SAR (pH 4.0, 3.0, or 2.0) obviously improved the rice growth compared with the single treatment with SAR. Incorporation of Si into SAR treatment decreased malondialdehyde (MDA) content; increased soluble protein and proline contents; promoted CAT, POD, SOD, and APX activity; and maintained the K, Ca, Mg, Fe, Zn, Cu content balance in leaves of rice seedlings under SAR stress. The moderate concentration of Si (2.0 mM) was better than the low and high concentration of Si (1.0 and 4.0 mM). Therefore, application of Si could be a better strategy for maintaining the crop productivity in acid rain regions.     

Salicylic acid-mediated alleviation of cadmium toxicity in hemp plants in relation to cadmium uptake,photosynthesis, and antioxidant enzymes

To assess the role of salicylic acid (SA) in alleviating cadmium (Cd) toxicity in hemp (Cannabis sativa L.) plants, the growth parameters, Cd accumulation, photosynthetic performance and activities of major antioxidant enzymes were investigated in hemp seedlings treated with 500 μM SA, under 0, 25, 50, and 100 mg Cd kg⁻¹ sands (DW) conditions, respectively. Cd exposure resulted in a small reduction in biomass (12.0–26.9% for root, and 8.7–29.4% for shoot, respectively), indicating hemp plants have innate capacity to tolerant Cd stress. This was illustrated by little inhibition in photosynthetic performance, unchanged malondialdehyde content, and enhancement of superoxide dismutase (SOD) and peroxidases (POD) activities in hemp plants. Cd content in root is 25.0–29.5 times’ higher than that in shoot, suggesting the plant can be classified as a Cd excluder. It is concluded that SA pretreatment counteracted the Cd-induced inhibition in plant growth. The beneficial effects of SA in alleviating Cd toxicity can be attributed to the SA-induced reduction of Cd uptake, improvement of photosynthetic capacity, and enhancement of SOD and POD activities.     

重金属镉（Cd）和增强UV—B辐射复合对大豆生长和生理代谢的影响

研究了大豆的生长、生物量、抗氧化酶活性和吲哚乙酸（IAA）氧化酶活性在Cd^2 、UV－B辐射和二者复合胁迫（Cd UV-B)下的变化。结果表明,Cd^2 和UV－B辐射都抑制大豆生长,并显著抑制根的伸长,二者复合后加强了对根伸长的抑制。UV－B辐射显著增强了POD、SOD活性,Cd^2 对POD活性影响不明显,但却拮抗UV－B对POD活性的诱导,SOD活性在各种胁迫下显著增强。虽然Cd%2 对叶片类黄酮含量影响不明显,但对UV－B诱导的类黄酮合成有一定影响。IAA氧化酶活性在复合作用下下降,可能是复合胁迫影响大豆生长的重要因素之一。     

Aluminum alleviates boron-deficiency induced growth impairment in tea plants

Interaction between aluminum (Al) and boron (B) in Al accumulator species has not been characterized so far. In this work, tea [Camellia sinensis (L.) O. Kuntze] plants were cultivated hydroponically and treated with adequate (control) or low B supply (-B) without or with 300 μM Al (-B+Al) for 14 weeks. Growth of B-deficient plants was completely resumed by Al supplementation or even surpassed control plants regarding shoot biomass. Net photosynthetic rate was negatively influenced by the low B supply, and the Al treatment increased it up to the level of the control plants that was reflected in the higher content of saccharides. The activity of ascorbate peroxidase (APX) in the younger leaves decreased at the low B supply accompanied with an increased H₂O₂ content. The Al treatment increased the APX activity up to the level of the control plants simultaneously with the reduction of H₂O₂. Activities of superoxide dismutase (SOD) and peroxidase (POD) increased in the low B plants and the Al treatment augmented this effect. The content of malondialdehyde (MDA) in the leaves increased by low B but declined upon the Al treatment. In the Al-treated plants, the activity of nitrate reductase (NR) and the content of free α-amino acids exceeded those of the control plants, and nitrite concentration diminished. The shoot and root B content of the B-deficient plants supplemented with Al was similar with the B-sufficient ones. The results demonstrate that the up-regulation of C and N metabolism, the activation of antioxidative defense, and the enhancement of B uptake and transport were mechanisms for growth amelioration of the B-deficient plants by Al supplementation in tea.     

Effects of salicylic acid on paraquat tolerance in<Emphasis Type="Italic">Arabidopsis thaliana</Emphasis> plants

Foliar spraying ofArabidopsis thaliana (Columbia ecotype) plants with a 1.0-mM salicylic acid (SA) solution significantly improved their tolerance to subsequent paraquat (PQ)-induced oxidative damage. Leaf injuries, including losses of chlorophyll, protein, and fresh weight, were reduced. Our analysis of antioxidant enzymes in the leaves showed that SA pre-treatment effectively retarded rapid decreases in the activities of Superoxide dismutase (SOD), catalase, and ascorbate peroxidase that are normally associated with PQ exposure. In addition, guaiacol peroxidase activity was remarkably increased. In a native gel assay of peroxidase (POD) isozymes, staining activity of the POD1 isozyme, which disappeared in plants exposed only to 10 μM PQ, was significantly recovered by the 1.0-mM SA pre-treatment POD2 isozyme activity was also pronounced in all SA-treated plants compared with the control. A 12-h SA pre-treatment, without subsequent PQ stress, also caused a small increase in the endogenous H₂O₂ content that accompanies the symptoms of mild leaf injuries. This enhanced level occurred in parallel with a slight SOD increase and a catalase decrease. From our results, it can be assumed that, due to the small increase in SOD as well as catalase inactivation via SA pre-treatment, a moderate increase in H₂O₂ levels may occur. In turn, a large induction of guaiacol peroxidase leads to enhanced PQ tolerance inA. thaliana plants.     

Aluminium effects on transmembrane potential in cells of fibrous roots of sugar beet

The effect of aluminium (Al) on the electrical transmembrane potential of epidermal and outer cortical root cells of intact seedlings of sugar beet (Beta vulgaris L. cv. Monohill) was studied. The potential difference to the surrounding medium was recorded with microelectrodes inserted into the vacuoles (PD_v) and cytoplasm (PD_c) of intact roots. Both long-term effects of AlCl₃ (100, μM present during cultivation) and immediate effects of AlCl₃ (10, 50, or 100 μM present in the assay medium), were measured. The effect of Al was measured at pH 4.0, 5.0 and 6.5 in order to obtain information on the toxicity of different Al forms existing at different pH values. Low pH and/or the presence of AlCl₃ during cultivation caused large depolarizations of the PD_v. Since the immediate effect of 2,4-dinitrophenol (DNP) on the resting potential of cells from Al-cultivated plants was negligible, it is likely that Al affects the metabolic component of the transmembrane potential. Aluminium also had an immediate effect on the PD in root cells of plants cultivated without Al. Addition of 10 or 50 μM Al to the assay medium caused hyperpolarization of PD_v in the presence of 0.5 mM Ca²⁺ at all pH values studied, depolarization of PD_c at pH 6.5, and hyperpolarization of PD_c at lower pH. At 1 mM Ca²⁺, or in the presence of K⁺ (≥ 2 mM), however, the same Al concentrations had little effect on PD_c. The strongest depolarizing effects of 10 or 50 μM Al in short-term treatments were obtained at pH 6.5, and were probably due to the soluble species Al(OH)₃, which is more frequent at pH 6.5 than at a lower pH. Addition of 50 μM Al caused alkalinization of the root medium at pH 6.5, but not at pH 4.0. Therefore, it is possible that Al at pH 6.5 is bound to, or translocated across, the membrane without the accompanying hydroxide ions. It is likely that most of the Al is bound to the root cells, since removal of Al from the buffer surrounding the roots did not cause the changed PD values to return to the original values. Aluminium also interacts with effects of Ca²⁺ and K⁺ on the membrane potential, since changes in PD, induced by changes in concentrations of Ca²⁺ and K⁺ are different in the absence and presence of Al.     

Physiological and biochemical roles of nitric oxide against toxicity produced by glyphosate herbicide in <Emphasis Type="Italic">Pisum sativum</Emphasis>

The present study assessed the response of pea plants exposed to herbicide induced oxidative stress in the plants present in agriculture field. We analysed the effect of exogenous nitric oxide (NO) regulated chlorophyll and protein content, nitrate reductase enzyme activity and antioxidant enzyme activity in herbicidetreated green pea (Pisum sativum L.). Glyphosate (0.25 mM) treatment alone or in combination with 250 μM sodium nitroprusside (SNP, 250 μM with glyphosate) was given to pea and we observed the changes in biophysical and biochemical parameters. During oxidative stress ion leakage is the first step of cellular damage. Supplementation of SNP with glyphosate significantly reduced ion leakage and moderately reduced H2O2 and malondialdehyde (MDA) content. SNP also increased chlorophyll content and antioxidant enzymes viz. superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (POD) activity as compared to herbicide treatment alone. The present result suggests that NO protects pea plants from damage caused by glyphosate.     

An assessment of Agropyron cristatum tolerance to cadmium contaminated soil

A pot experiment was conducted in a greenhouse to assess the tolerance of Agropyron cristatum plants to cadmium contaminated soils (0, 5, 10, 25, 50, 100, 150, and 200 mg kg^?1) for 100 d. Results indicate that Cd in concentrations of 5–50 mg kg^?1 had no significant impact on growth, relative membrane permeability (RMP), lipid peroxidation measured as malondialdehyde (MDA) content, and chlorophyll (Chl) content relative to the control. Exposure of these plants to high concentrations of Cd (100–200 mg kg^?1) caused a small reduction in growth and Chl content and a slight enhancement of RMP and MDA content compared with the control. In addition, superoxide dismutase (SOD) and peroxidase (POD) activities show an increasing trend with the increase of Cd content in soil. The Cd content in the roots was 4.7–6.1 times higher than that in the shoots under all Cd treatments suggesting that the plant can be classified as a Cd excluder. The translocation factor was low and similar at 25–200 mg kg^?1 Cd treatments. In summary, A. cristatum plants tolerated Cd stress and might have potential for the phytoremediation of Cd contaminated soils.     

镉及其与钙组合对褐脉少花龙葵毛状根生长、抗氧化酶活性和吸收镉的影响

为了探讨利用褐脉少花龙葵毛状根来修复重金属镉(Cd)污染的可能性,采用溶液培养法研究了Cd单独及其与钙(Ca)组合对褐脉少花龙葵毛状根生长、抗氧化酶超氧化物歧化酶(SOD)和过氧化物酶(POD)活性及对Cd吸收的影响。结果表明,Cd≤50μmol/L时能促进毛状根生长,而高于100μmol/LCd则抑制毛状根生长,使其侧根根尖变褐和变短,数目减少。与对照相比,不同浓度Cd培养的毛状根可溶性蛋白含量和SOD活性先升高后逐渐下降;其丙二醛(MDA)含量显著提高;100μmol/LCd使毛状根POD活性逐渐升高,但300μmol/LCd则使毛状根POD活性逐渐降低。与对照(仅添加100μmol/L或300μmol/LCd的毛状根)相比,Cd和10～30mmol/LCaCl2组合培养使毛状根可溶性蛋白含量和MDA含量降低;但提高其SOD活性;而100μmol/LCd和10～30mmol/LCaCl2结合培养的毛状根POD活性均比对照低;而300μmol/LCd和10～30mmol/LCaCl2结合培养的毛状根POD活性则均比对照提高。原子吸收分光光度法测定结果表明,毛状根吸收和吸附的重金属Cd含量随着培养基中Cd浓度的升高而增加。但外源加入10～30mmol/LCaCl2能减少毛状根对Cd的吸收,并调节其抗氧化酶SOD和POD活性,降低其膜脂过氧化水平而解除重金属Cd对毛状根生长的抑制或毒害。     

Calcium application enhances growth and alleviates the damaging effects induced by Cd stress in sesame (Sesamum indicum L.)

In this study, the effects of calcium (Ca²⁺) application on acquired systemic tolerance mechanism to cadmium (Cd) stress in sesame (Sesamum indicum L.) were studied. The Cd stress reduced the root and shoot growth of sesame, and plant contents of photosynthetic pigments; however, the application of Ca²⁺ improved these parameters under Cd stress condition. The hydrogen peroxide, malondialdehyde and soluble sugar contents were higher under Cd stress, and were reduced by Ca²⁺ treatment. The antioxidant enzyme activities in the leaves of sesame, superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), ascorbate peroxidase (APX) and glutathione reductase (GR) were higher under Cd stress, whereas reduced concentration was observed in Ca²⁺-treated plants. Cd stress increased the contents of diacylglycerol and sterol ester; however Ca²⁺ treatment resulted in a significant increase in phosphatidylcholine, phosphatidylethanolamine, phosphatidylglycerol, phosphatidylinositol and phosphatidylserine. Our results indicated that application of calcium enables sesame plants to withstand the deleterious impact of cadmium through upregulating acquired systemic tolerance system as lipid fractions (galactolipids, phospholipids, neutral lipids), antioxidant enzymes (SOD, POD, CAT, APX, GR) hence protect membrane functions.