Biosorption of cadmium and chromium in duckweed Wolffia globosa

The biosorption of cadmium (Cd) and chromium (Cr) by using dried Wolffia globosa biomass were investigated using batch technique. The effects of concentration and pH solution on the adsorption isotherm were measured by determining the adsorption isotherm at initial metal concentrations from 10 to 400 mg/L and pH 4 to 7 for Cd, and pH 1.5 to 6 for Cr. The adsorption equilibria were found to follow Langmuir models. The maximum adsorption capacity (Xm) at pH 7 in W. globosa-Cd system was estimated to be 80.7 mg/g, while the maximum removal achieved at pH 4, pH 5, and pH 6 were 35.1, 48.8, and 65.4 mg/g, respectively. The Xm at pH 1.5 in W. globosa--Cr system was estimated to be 73.5 mg/g, while the maximum removal achieved at pH 3, pH 5, and pH 6 were 47.4, 33.1, and 12.9 mg/g, respectively. The effects of contact times on Cd and Cr sorption indicated that they were absorbed rapidly and more efficiently at lower concentrations.     

锌、镉及其复合胁迫下白花泡桐幼苗的生理及富集特征

采用水培培养的试验方法,研究白花泡桐幼苗在锌 (Zn)、镉 (Cd) 单一及复合胁迫下的生理生化响应及对重金属的富集、转移特征变化。结果表明,单一及复合重金属胁迫下,白花泡桐的生物量、株高及过氧化物酶 (Peroxidase,POD) 活性均随处理浓度的增加而降低。在复合污染下,Zn、Cd在植株的株高及生物量上表现出拮抗作用。与对照比,单一胁迫下,随着Zn浓度的增加,白花泡桐叶绿素含量和过氧化氢酶 (Catalase,CAT) 活性先增加后减小,超氧化物歧化酶 (Superoxide dismutase,SOD) 活性升高,地上部丙二醛 (Malondialdehyde,MDA) 含量先减小后增加;随着Cd浓度的增加,叶绿素含量和过氧化氢酶 (CAT) 活性升高,超氧化物歧化酶 (SOD) 活性及地上部丙二醛 (MDA) 含量先增加后减小,复合胁迫下,则表现出更加复杂的生理响应。白花泡桐幼苗对Cd的富集部位集中在根部;对Zn的富集部位集中在地上部,且转移系数大于1.00;Zn的加入会促进重金属向地上部分的转移;白花泡桐具有对复合重金属污染地进行有效的生态恢复的潜力。     

Effects of Cadmium,Chromium and Lead on Growth,Metal Uptake and Antioxidative Capacity in <Emphasis Type="Italic">Typha angustifolia</Emphasis>

This study investigates the modulation of antioxidant defence system of Typha angustifolia after 30 days exposure of 1 mM chromium (Cr), cadmium (Cd), or lead (Pb). T. angustifolia showed high tolerance to heavy metal toxicity with no visual toxic symptom when exposed to metal stress, and Cd/Pb addition also increased plant height and biomass especially in Pb treatment. Along with increased Cr, Cd, and Pb uptake in metal treatments, there was enhanced uptake of plant nutrients including Ca and Fe, and Zn in Pb treatment. A significant increase in malondialdehyde (MDA) content and superoxide dismutase (SOD) and peroxidase (POD) activities were recorded in plants subjected to Cr, Cd, or Pb stress. Furthermore, Pb stress also improved catalase (CAT), ascorbate peroxidase (APX), and glutathione peroxidase (GPX) activities; whereas Cr stress depressed APX and GPX. The results indicate that enzymatic antioxidants and Ca/Fe uptake were important for heavy metal detoxification in T. angustifolia, stimulated antioxidative enzymes, and Ca, Fe, and Zn uptake could partially explain its hyper-Pb tolerance.     

Long time combined action of cadmium and ultraviolet radiation on barley plants

In a greenhouse experiment the development of biomass and grain yield was studied under a long-time combined action of medium-wave UV-radiation and cadmium (exposure levels of the agents were, respectively, 0.65-1.30 W/m2, 5 and 50 mg/kg of soil). The influence of the metal on the UV-radiation induced inhibition of the vegetative mass development was found to be dependent on the duration of stress: with increase in the exposure time the cadmium ability for cushioning negative effects of irradiation decreases. Simultaneously the contribution of the metal and its interaction with UV-radiation to the variability in the observed indicator (biomass) becomes much less significant than that of irradiation. Considerable independent of cadmium concentration reduction in the grain yield becomes evident at a rate of medium-wave UV-radiation intensity of 0.65 W/m2, whereas at UV-radiation exposure levels of 1.30 W/m2 and the heavy metal concentration of 50 mg/kg in soil practically total inhibition of grain productivity occurred. As for grain formation, relative effects of irradiation were somewhat higher than these of cadmium and its interaction with UV-radiation.     

东海赤潮高发区春季叶绿素a和初级生产力的分布特征

2002年4-5月对东海海域进行了综合调查,分析了海区叶绿素a和初级生产力的分布特性．结果表明,大面站表层平均叶绿素a浓度为1．086mg·m-3．分级叶绿素a结果显示．春季东海浮游植物以微型和微微型(<20μm)占优势,其对海区叶绿素a的贡献为64％,超微型浮游植物(<5μm)占浮游植物生物量的27％．营养盐分布和浮游动物的摄食压力影响了叶绿素a及其粒级结构的分布．平均初级生产力为10．091mg·m-3·h-1。赤潮跟踪的R-03、RL-01、RG-01站的平均初级生产力为399．984mg·m-3·h-1．光和营养盐成为叶绿素和初级生产力平面分布的主要限制因子．表层叶绿素a和初级生产力均在调查海区的123·E纵断面冲淡区产生高值区．DC-11站浮游植物生物量异常高,表层叶绿素a达到9．082mg·m-3,初级生产力为128．79mg·m-3·h-1．但并未出现水色异常．     

Biosorption of Ni, Cr and Cd by metal tolerant Aspergillus niger and Penicillium sp. using single and multi-metal solution

Fungi including Aspergillus and Penicillium, resistant to Ni2+, Cd2+, and Cr6+ were isolated from soil receiving long-term application of municipal wastewater mix with untreated industrial effluents of Aligarh, India. Metal tolerance in term of minimum inhibitory concentration (MIC) was 125-550 microg/ml for Cd, 300-850 microg/ml for Ni and 300-600 microg/ml for Cr against test fungi. Two isolates, Aspergillus niger and Penicillium sp. were tested for their Cr, Ni and Cd biosorption potential using alkali treated, dried and powdered mycelium. Biosorption experiment was conducted in 100 ml of solution at three initial metal concentrations i.e., 2, 4 and 6 mM with contact time (18 hr) and pretreated fungal biomass (0.1g) at 25 degrees C. Biosorption of all metals was found higher at 4 mM initial metal concentration as compared to biosorption at 2 and 6 mM concentrations. At 4 mM initial metal concentration, chromium biosorption was 18.05 and 19.3 mg/g of Aspergillus and Penicillium biomasses, respectively. Similarly, biosorption of Cd and Ni ions was also maximum at 4 mM initial metal concentration by Aspergillus (19.4 mg/g for Cd and 25.05 mg/g of biomass for Ni) and Penicillium (18.6 mg/g for Cd and 17.9 mg/g of biomass for Ni). In general, biosorption of metal was influenced by initial metal concentration and type of the test fungi. The results indicated that fungi of metal contaminated soil have high level of metal tolerance and biosorption properties.     

Accumulation of cadmium and its effects on growth, development and hemolymph biochemical compositions in Boettcherisca peregrina larvae （Diptera： Sarcophagidae）

Newly emerged larvae of the fleshfly, Boettcherisca peregrina were exposed to two different CdCl2 concentrations of 100μg/g and 400 mg/g diet fresh weight （DFW）. They were administered in the diets until the end of larval stage. Cd-exposed larvae accumulated significant amounts of Cd and this accumulation increased with the exposure dose and time. The body weights were lightened and lengths of larvae were shortened considerably after Cd exposure, especially at the higher Cd concentration. The total larval duration was also extremely affected due to Cd exposure. The average duration was prolonged significantly by 14 h at the lower Cd concentration, while it was increased by 33.7 h over controls at the higher Cd concentration. A significant decrease in contents of either soluble proteins, total lipids or caloric values in the hemolymph occurred due to Cd exposure throughout the entire tested period but after 120 h of Cd exposure. In contrast, when exposed to Cd with its higher concentration, total sugar contents in the hemolymph were increased strikingly over the whole tested time, except after 96 h of Cd exposure, while they were not apparently altered except after 24 h of Cd exposure at the lower concentration. Thus, it is suggested that Cd exposure shows significant adverse impact on the growth and development, as well as metabolism, in larvae of this fleshfly, depending on its exposure time and dose.     

Effects of Municipal Sewage Sludge Doses on the Chlorophyll Contents and Heavy Metal Concentration of Sugar Beet (Beta vulgaris var. saccharifera)

The present study was conducted to assess the suitability of sewage sludge amendment (SSA) in soil for Beta vulgaris var. saccharifera (sugar beet) by evaluating the heavy metal accumulation and physiological responses of plants grown at a 10%, 25%, and 50% sewage sludge amendment rate. The sewage sludge amendment was modified by the physicochemical properties of soil, thus increasing the availability of heavy metals in the soil and consequently increasing accumulation in plant parts. Cd, Pb, Ni, and Cu concentrations in roots were significantly higher in plants grown at 25% as compared to 50% SSA; however, Cr and Zn concentration was higher at 50% than 25% SSA. The concentrations of heavy metal showed a trend of Zn > Ni > Cu > Cr > Pb > Cd in roots and Zn > Cu > Ni > Cr > Pb > Cd in leaves. The only instance in which the chlorophyll content did not increase after the sewage sludge treatments was 50%. There were approximately 1.12-fold differences between the control and 50% sewage sludge application for chlorophyll content. The sewage sludge amendment led to a significant increase in Pb, Cr, Cd, Cu, Zn, and Ni concentrations of the soil. The heavy metal accumulation in the soil after the treatments did not exceed the limits for the land application of sewage sludge recommended by the US Environmental Protection Agency (US EPA). The increased concentration of heavy metals in the soil due to the sewage sludge amendment led to increases in heavy metal uptake and the leaf and root concentrations of Ni, Zn, Cd, Cu, Cr, Pb, and Zn in plants as compared to those grown on unamended soil. More accumulation occurred in roots and leaves than in shoots for most of the heavy metals. The concentrations of Cd, Cr, and Pb were more than the permissible limits of national standards in the edible portion of sugar beet grown on different sewage sludge amendment ratios. The study concludes that the sewage sludge amendment in the soil for growing sugar beet may not be a good option due to risk of contamination of Cr, Pb, and Cd.     

Calcium influence on the dry mass content and surface area of nuclei and cytoplasm during differentiation of cortex cells in pea (Pisum sativum L.) roots treated with heavy metals

The effect of Ca addition to Cd, Cr and Pb solutions on the nuclear and cytoplasmic dry mass content and its concentration as well as on these organelles dimensions were studied in cortex cells of pea roots. Ca alone, at the concentration 10(-8)M brought about a decrease (in comparison to water) in the dry mass content of nuclei and its concentration, but the increment was almost twice in the dry mass content of cytoplasm; however, it has no significant effect on its concentration. Ca ions addition does not change the surface area of nuclei except the 1st and 5th mm segments but causes a doubling of the area occupied by cytoplasm. In response to Ca addition to Cd or Cr solutions a further diminution of nuclear dry mass content takes place. Only in the case of Pb nuclear dry mass increases in the 7th mm or is similar in remaining root segments. The diminution of nuclear dry mass content due to Ca presence in metal solutions is accompanied by a lowering in its concentration, although in the presence of Cd and Pb the diminution is not significant. Ca ions addition results in an increase in cytoplasmic dry mass content. No such regularities were observed in the 1st (Cd, Pb) and 3rd (Cr) root segments. In response to Ca ions the concentration of cytoplasmic dry mass content increased insignificantly in differentiation zone and underwent reducation in the meristematic zone--in the 1st mm (Cr) and 3rd (Cd). After Ca addition to studied metal solutions the decrease in nuclear dimensions was visible only in Cd or Pb treated cells in the 3rd and 7th or in the 1st mm, respectively. An increase in nuclear size occurred only in Cr treated cells in the 7th mm. Enrichment of heavy metals with Ca caused the marked enlargement in cytoplasmic area in differentiation zone but the increment in it in meristematic zone was observed only in Cd (1st, 3rd) and Cr (1st) treated cells.     

Cd、Cr(VI)单一及复合污染对菹草叶绿素含量和抗氧化酶系统的影响

主要研究了 Cd、Cr( VI)单一及复合污染对菹草叶绿素含量和抗氧化酶系统的影响 ,研究结果表明 :随 Cd、Cr( VI)胁迫浓度的增加 ,菹草总叶绿素含量下降 ,单一 Cd处理 SOD活性下降 ,POD和 CAT活性表现出先升后降的趋势 ,Cd、Cr( VI)复合污染的效应明显大于单一污染的效应。     

镉污染对水稻土微生物量、酶活性及水稻生理指标的影响

水稻盆栽条件下,研究了外源Cd不同处理对土壤微生物学指标、土壤酶活性及部分水稻生理指标的影响.结果表明,土壤微生物量C和N开始随Cd浓度增加而上升,到一定浓度时则随Cd浓度增加而下降,其转折点因土壤性质有所差异.同时土壤酶活性变化规律与土壤微生物量C、N变化规律相似,但其转折点浓度因土壤类型及土壤酶种类不同而有差异.Cd污染后的变异系数依次为:脱氢酶＞酸性磷酸酶＞脲酶.土壤呼吸作用强度和代谢熵都随Cd浓度增大而缓慢增加.水稻叶绿素含量随Cd处理浓度增加表现出先上升后下降,其转折点受供试土壤性质不同而不同;脯氨酸含量与过氧化物酶活性随着Cd处理浓度增大而增加.Cd污染后水稻生理指标的变异系数在黄松田水稻土中依次为过氧化物酶活性＞叶绿素含量＞脯氨酸含量;黄红壤性水稻土中依次为过氧化物酶活性＞脯氨酸含量＞叶绿素含量.相关分析表明,种植水稻条件下Cd污染对土壤微生物量、酶活性及水稻生理指标的影响是相辅相成的.     

Multi-Wall Carbon Nanotubes Effects on Plant Seedlings Growth and Cadmium/Lead Uptake In Vitro

The effects of multi-wall carbon nanotubes (MWCNTs) on plant growth and Cd/Pb accumulation was investigated on seedlings of three plant species including Brassica napus L., Helianthus annus L. and Cannabis sativa L. The experiment consisted of MWCNTs on three concentration levels (0, 10, 50 mg/L) and 200 μM CdCl₂ or 500 μM Pb(NO₃)₂. MWCNTs application effectively improved root and shoot growth inhibited by Cd and Pb salts. In B. napus, total chlorophyll (Chl) content increased by both MWCNTs 10 and 50 mg/L exposure under cadmium or lead stress. MWCNT 10 mg/L mitigated the deleterious effects of Cd ions on total chlorophyll content of H. annus and C. sativa. Wherease higher concentration of MWCNTs decreased Chl content under either Cd or Pb treatments on sunflower seedlings. MWCNT10 effectivly raised cadmium accumulation in seedlings of all three species. MWCNT10 and 50 mg/L also caused higher Pb accumulation in canola and cannabis seedlings, respectively. Based on the results, it seems that the effects of MWCNTs on growth parameters and heavy metal accumulation in plant seedlings is strongly depends on heavy metal type, MWCNTs concentration and plant species.     

Comparison of EDTA- and Citric Acid-Enhanced Phytoextraction of Heavy Metals in Artificially Metal Contaminated Soil by Typha Angustifolia

A pot experiment was conducted to study the performance of EDTA and citric acid (CA) addition in improving phytoextraction of Cd, Cu, Pb, and Cr from artificially contaminated soil by T. angustifolia. T. angustifolia showed the remarkable resistance to heavy metal toxicity with no visual toxic symptom including chlorosis and necrosis when exposed to metal stress. EDTA-addition significantly reduced plant height and biomass, compared with the control, and stunted plant growth, while 2.5 and 5 mM CA addition induced significant increases in root dry weight. EDTA, and 5 and 10 mM CA significantly increased shoot Cd, Pb, and Cr concentrations compared with the control, with EDTA being more effective. At final harvest, the highest shoot Cd, Cr, and Pb concentrations were recorded in the treatment of 5 mM EDTA addition, while maximal root Pb concentration was found at the 2.5 mM CA treatment. However, shoot Cd accumulation in the 10 mM CA treatment was 36.9% higher than that in 2.5 mM EDTA, and similar with that in 10 mM EDTA. Shoot Pb accumulation was lower in 10 mM CA than that in EDTA treatments. Further, root Cd, Cu, and Pb accumulation of CA treatments and shoot Cr accumulation in 5 or 10 mM CA treatments were markedly higher than that of control and EDTA treatments. The results also showed that EDTA dramatically increased the dissolution of Cu, Cr, Pb, and Cd in soil, while CA addition had less effect on water-soluble Cu, Cr, and Cd, and no effect on Pb levels. It is suggested that CA can be a good chelator candidate for T. angustifolia used for environmentally safe phytoextraction of Cd and Cr in soils.     

蒌蒿对镉的富集特征及亚细胞分布特点

以镉(Cd)富集植物蒌蒿(Artemisia selengensis)为试材, 采用超声波细胞破碎处理和超速离心的方法, 对蒌蒿根和叶中亚细胞水平的Cd分布状况进行研究, 同时测定Cd在蒌蒿不同器官中的富集效果。结果表明, 在30 mg·kg^–1Cd胁迫下, 蒌蒿叶片中Cd的富集浓度是根和茎中的2–3倍, 但因叶片所占植株的生物量比例较小, 其对Cd的积累量远小于茎和根; Cd在蒌蒿叶片细胞壁、胞液和细胞器中含量比为16:5:1。细胞壁固定是叶片对Cd的主要防御机制。随着Cd处理浓度的增加, 细胞壁和胞液中的Cd含量大幅上升, 但细胞器中Cd含量仍维持在较低水平。长时间和高浓度的Cd胁迫可使细胞壁解毒机制失活并诱导细胞器中的Cd含量增加, 导致植株死亡。根中液泡的Cd贮存量较大, 解毒效果显著。     

Metal tolerance and biosorption potential of filamentous fungi isolated from metal contaminated agricultural soil

Heavy metal analysis of agricultural field soil receiving long-term (>20 years) application of municipal and industrial wastewater showed two- to five-fold accumulation of certain heavy metals as compared to untreated soil. Metal-resistant fungi isolated from wastewater-treated soil belonged to genera Aspergillus, Penicillium, Alternaria, Geotrichum, Fusarium, Rhizopus, Monilia and Trichoderma. Minimum inhibitory concentrations (MIC) for Cd, Ni, Cr, Cu, and Co were determined. The MIC ranged from 0.2 to 5 mg ml(-1) for Cd, followed by Ni (0.1-4 mg ml(-1)), Cr (0.3-7 mg ml(-1)), Cu (0.6-9 mg ml(-1)) and for Co (0.1-5 mg ml(-1)) depending on the isolate. Aspergillus and Rhizopus isolates were tested for their metal biosorption potential for Cr and Cd in vitro. Biosorption experiments were conducted with initial metal concentrations of 2, 4, 6 and 8 mM with a contact time of 4 h and wet fungal biomass (1-5 g) at 25 degrees C. Maximum biosorption of Cr and Cd ions was found at 6 mM initial metal concentration. Aspergillus sp.1 accumulated 1.20 mg of Cr and 2.72 mg of Cd per gram of biomass. Accumulation of these two metals by very tolerant Aspergillus sp.2 isolate was at par with relatively less tolerant Aspergillus sp.1 isolate. Rhizopus sp. accumulated 4.33 mg of Cr and 2.72 mg of Cd per g of biomass. The findings indicated promising biosorption of cadmium and chromium by the Rhizopus and Aspergillus spp. from aqueous solution. There is little, if any, correlation between metal tolerance and biosorption properties of the test fungi.     

Pb~(2+)、Cr~(6+)、Hg~(2+)和Cu~(2+)对碱蓬幼苗生长及生理生化指标的影响

以水培法及分光光度法培养、测定碱蓬幼苗在重金属胁迫下的株高、鲜重及根数,叶绿素、可溶性蛋白和丙二醛含量等各项生长指标以及过氧化物酶、过氧化氢酶的活性变化.结果表明:Pb2+、Cr6+、Hg2+和Cu2+使碱蓬植株生长出现明显抑制效果的临界浓度分别为:45 mg/kg、15 mg/kg、10 mg/kg和5 mg/kg。此浓度胁迫下,碱蓬植株鲜重降低25%~30%、根数减少12%~34%。重金属处理后,碱蓬的叶绿素和可溶性蛋白含量下降、丙二醛含量上升,且处理与对照间差异显著。Pb2+、Cr6+、Hg2+、Cu2+处理的叶绿素总量分别是对照的61%、59%、55%和67%,可溶性蛋白含量分别是对照的66.7%、58.3%、41.7%和75%,而丙二醛含量分别是对照的167%、147%、114%和131%。4种重金属胁迫下的碱蓬植株体内过氧化物酶活性均高于对照,而过氧化氢酶活性低于对照。     

镉诱导植物的自由基过氧化损伤

紫羊茅(Festuca rubra L.)有对重金属敏感(“S59”)和忍耐(“Merlin”)两个品种。以0～2.5mmol/LCd~(2 )的营养液分别培养“S59”和“Merlin”幼苗,随着Cd~(2 )浓度增加和处理时间延长,幼苗生长量相应下降。0.25mml/L Cd~(2 )对“S59”的生长抑制与0.5mmol/L Cd~(2 )对“Merlin”的抑制相似,表明“Merlin”比“S59”更能耐受Cd~(2 )的毒害。在Cd~(2 )抑制生长的同时,幼苗的MDA(丙二醛,膜脂过氧化产物)和POD(过氧化物酶)活性急剧上升,CAT(过氧化氢酶)和SOD活性降低,蛋白质含量明显下降。MDA大幅度上升是Cd~(2 )培养幼苗突出的生理变化之一,2.5mmol/L Cd~(2 )培养幼苗6d,“Merlin”的MDA为对照的209％,而“S59”为对照的243％。MDA的积累与培养幼苗的Cd~(2 )浓度成密切正相关,与幼苗的生长量呈负相关。当SOD活性平稳或略为上升时,MDA稳定;SOD活性开始下降,MDA便急剧上升。很可能自由基和MDA在Cd~(2 )毒害植物中充当了重要的角色。     

草甘膦对可食用蓝藻葛仙米生长和生理的影响

葛仙米（N．sphaeroides）的产量和产地面积逐年减少,这可能与当地广泛使用除草剂草甘膦有关。为此,本文测定了不同浓度（0．15、0．30、0．45、0．6mmol／L）的草甘膦处理的葛仙米的颗粒大小、干重、叶绿素荧光、叶绿素浓度。所有测量参数与浓度和时间显著相关：0．15mmol／L处理组的颗粒直径较对照组小15％（2d后）;叶绿素a浓度和最大量子产率（Fv／Fm）在最高浓度组（0．6mmol／L）4d后开始受到影响;第8天,相对生长速率（以干重计算,大于0．15mmol／L）、光合作用活性（大于0．3mm01／L）均受显著抑制,其中0．15mmol／L处理组相对生长下降60％,而更高浓度处理组出现负生长,0．6mm01／L组藻体漂白死亡。结合实验结果,文章讨论了草甘膦的毒性机理及其对葛仙米（N．sphaeroides）的潜在影响。     

Heavy metal action on the dry mass content and surface area of nuclei and cytoplasm during differentiation of cortex cells in pea (Pisum sativum L.) roots

The cortex cells of pea roots (Pisum sativum L.) grown for 144 h in the presence of cadmium, chromium and lead at the concentration 10(-4) M were the object of the present studies. Applied metals reduced dry mass content and concentration of nuclei in meristematic and differentiation zones. Chromium only enhanced nuclear mass concentration in the differentiation zone. The metals also made dry mass content and concentration of cytoplasm reduce, but they diminished mostly the concentration of cytoplasm in the meristematic zone and its dry mass in differentiation zone. Stimulation of cytoplasmic dry mass concentration was visible in the 1st mm (Cr) and 7th mm (Cd). Moreover, chromium caused a marked increase of cytoplasmic dry mass content in the 3rd mm of root. The studied metals reduced nuclear size, calculated as surface area, in the meristematic and differentiation zones. The increment of nuclear dimensions was observed only in the 1-3rd mm (Pb), 3rd (Cr) and 7th mm (Cd). In the presence of the applied metals the surface area of cytoplasm increased only in the 3rd mm and in 5th mm (chromium only). The present observations have shown that the toxicity of studied metals is as follows; Cd greater than Pb greater than Cr (nucleus - dry mass content and concentration, cytoplasmic area), Pb greater than Cd greater than Cr (cytoplasmic dry mass content and concentration and Cd greater than Cr greater than Pb (nuclear dimensions).     

锌对镉胁迫下马蔺生长、镉积累及生理抗性的影响

通过溶液培养研究了不同浓度锌(Zn)对镉(Cd)胁迫下马蔺(Iris lacteavar. chinen-sis)生长、Cd积累及抗氧化酶活性等的影响.结果表明:加入1~100mg.L-1Zn后,Cd胁迫下马蔺地上部Cd含量变化不大,而地下部Cd含量显著增加并呈先增后降的趋势;1mg.L-1Zn处理下马蔺地下部Cd含量最高,比对照显著增加51.4%;Zn浓度高于1mg.L-1后Cd含量均出现不同程度的下降,但仍高于对照.与单独Cd处理(10mg.L-1)相比,添加低浓度Zn(1~10mg.L-1)后,马蔺地上部生物量和叶绿素含量呈增加趋势,丙二醛(MDA)含量降低;在10mg.L-1Zn处理下,叶绿素a、b含量达到峰值,分别增加5.21%和22.27%,MDA含量降低25.46%,表明低浓度Zn缓解了Cd对马蔺的毒害.随Zn浓度的增加,Zn对Cd毒害的缓解作用逐渐降低,当溶液中Zn达到一定浓度(100mg.L-1)时,马蔺毒害加重,其生物量、叶绿素含量均下降,MDA含量显著增加.在试验胁迫浓度范围内超氧化物歧化酶(SOD)、过氧化物酶(POD)活性始终呈增加趋势,表明马蔺在受到Cd胁迫及Cd-Zn共存的条件下SOD和POD起着重要的抗氧化保护作用.