镉胁迫下杞柳对金属元素的吸收及其根系形态构型特征

采用水培方法,研究了杞柳(Salix integra)2个品种在0-90 μmol/L Cd处理下不同组织对Cd的吸收和积累规律,探讨了镉胁迫下杞柳根系形态学功能响应特征以及对矿质离子吸收的影响。结果发现,镉在杞柳2个品种不同组织的含量均表现为根>韧皮部>木质部>叶。2个品种地上部组织对镉的吸收和积累规律相似:在0-70 μmol/L Cd处理浓度范围内,随着溶液Cd浓度的增加,叶、木质部、韧皮部中镉的含量逐渐增加,到50 μmol/L时,镉在地上部组织的含量达到最高,当Cd处理浓度达90 μmol/L时,地上部各组织中Cd含量出现下降趋势。而2个品种根系对Cd的吸收则不同,"微山湖"品种在溶液Cd达70 μmol/L时,根系镉的积累量最大,在90 μmol/L时,根系Cd的积累量明显下降;"一枝笔"品种根系在0-90 μmol/L范围内,根系Cd的积累量均为增加趋势。通过分析2个品种根系形态学参数变化发现,Cd胁迫抑制了杞柳2个品种根的伸长,促进了"微山湖"品种根的径向生长,导致根系平均直径增加;进一步对叶片矿质营养状态分析发现, Ca、Mn的吸收受镉胁迫的影响较大,在高浓度镉胁迫下(50-70 μmol/L)"微山湖"和"一枝笔"对Ca和Mn的吸收明显下降;Cd胁迫对Fe在叶片的含量影响不明显;同时发现,在50 μmol/L Cd处理下,Cu²⁺在叶片的积累明显增加。由此可见,杞柳2个品种间对镉的吸收和积累差异主要体现在根系,地上部对镉毒害的响应差异不大。     

热带地区不同水稻品种对土壤镉胁迫的生理生化响应

以热带地区主栽品种博优225和矮糯为材料,采用盆栽试验研究了不同水稻品种对土壤外源重金属Cd胁迫的耐性机理。结果表明:在各浓度镉胁迫下,2个品种水稻都是根累积的镉含量要高于茎叶和稻壳、糙米,即根>茎叶>稻壳>糙米;随着镉胁迫浓度的增加,细胞膜受损的伤害程度越大,矮糯质膜透性略高于博优225;随着Cd浓度的升高,水稻叶片丙二醛(MDA)、脯氨酸含量逐渐增加,且博优225的增加幅度明显大于矮糯,超氧化物歧化酶(SOD)和过氧化物酶(POD)活性均呈上升趋势,且博优225明显高于矮糯;过氧化氢酶(CAT)活性呈下降趋势;表明同样条件下博优225受Cd毒害更严重。     

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。     

镉诱导的菊芋幼苗膜脂过氧化和抗氧化酶活性及过氧化物酶同工酶的改变

用含有不同浓度(0~400μmol/L)Cd(NO3)2的Hoagland营养液处理砂培的菊芋。处理50d后,测定植物体内镉积累量以及过氧化物酶(POD)、超氧化物歧化酶(SOD)、过氧化氢酶(CAT)活性,并对POD同工酶进行电泳分析。发现在Cd50~100μmol/L浓度内,随着镉浓度的升高,菊芋根和叶中镉的积累量显著增加,而随后积累量的增加有所减少。根和叶中MDA含量显著上升,说明镉引起了膜脂过氧化。0~100μmol/LCd处理,根和叶中POD活性随Cd浓度增加而增强,而在200~400μmol/LCd处理下有所减弱。根和叶SOD活性在50~200μmol/LCd处理下随Cd浓度增加而增强,而在400μmol/LCd处理下SOD活性明显受到抑制。根和叶CAT活性随Cd浓度升高而增强。电泳结果显示,POD同工酶变化明显,镉诱导出一条新酶带LP10。菊芋POD同工酶可以作为镉污染的土壤的生物指示剂。     

铜绿假单胞菌对镉胁迫苗期水稻根系活力及叶片生理特性的影响

为揭示耐镉铜绿假单胞菌缓解镉胁迫水稻的生理效应,以无镉处理为对照,通过添加菌液、空载体、菌剂及20μmol·L^-1 Cd进行水培试验,分析了菌株对苗期水稻根系活力及叶片生理特性的影响.结果表明:镉胁迫显著抑制了水稻的根系活力,降低了叶片光合效率、抗氧化酶活性及可溶性蛋白、类黄酮与总酚含量,提高了叶片丙二醛(MDA)和超氧阴离子(O2-)含量.与镉处理相比,添加菌液、菌剂处理的水稻根系活力分别提高了36.1%~42.5%、49.4%~53.0%;叶片净光合速率提高了118.5%~147.1%、137.6%~156.9%;可溶性蛋白含量提高了37.0%~49.3%、37.7%~72.6%.菌剂处理的水稻叶片超氧化物歧化酶(SOD)、过氧化物酶(POD)、过氧化氢酶(CAT)活性分别比Cd处理提高了36.9%~42.6%、82.7%~92.6%、43.3%~52.2%,菌液处理的SOD、POD、CAT则分别比Cd处理提高了25.8%~36.6%、40.9%~55.9%、24.0%~29.2%,菌剂对水稻叶片抗氧化酶的促进效应显著高于菌液;菌剂、菌液处理的水稻叶片MDA含量分别比Cd处理降低了44.8%~54.7%、29.4%~41.9%;O2-含量减少了9.9%~10.2%、3.0%~7.1%;菌剂处理后类黄酮、总酚含量分别比Cd处理提高了125.4%~135.7%、100.8%~119.4%;菌液处理后则分别提高了139.4%~146.7%、115.0%~134.7%.可见,铜绿假单胞菌及其菌剂通过提高苗期水稻根系活力、光合作用促进了苗期水稻的生长.铜绿假单胞菌通过增强水稻抗氧化酶活性、提高类黄酮和总酚等抗氧化物质含量,表现出显著的缓解镉胁迫效应.     

冬小麦幼苗根系适应土壤干旱的生理学变化

采用盆栽试验对冬小麦幼苗根系适应土壤干旱的生理学变化进行了初步研究。结果表明，随干旱胁迫的加剧，洛麦9133和济麦21幼苗根水势、根相对含水率和根系活力均降低，饱和亏、可溶性糖含量、脯氨酸含量、质膜透性以及SOD、POD活性均呈增加趋势。这说明，在干旱胁迫下，冬小麦幼苗根系通过降低水势、相对含水率和根系活力，增加渗透调节物质可溶性糖、脯氨酸含量和增强SOD、POD活性等生理上的变化以提高抗旱性，从而使冬小麦幼苗适应干旱逆境。     

硒对镉胁迫下水稻幼苗生长及生理特性的影响

采用溶液培养 ,研究不同浓度的硒和镉处理对稻苗的株高、叶片干重、叶绿素、还原糖、叶片丙二醛含量以及保护酶 SOD、POD、CAT活性的影响。结果表明 ,镉胁迫下稻苗矮化 ,镉毒害使叶片失绿 ,干重降低 ,还原糖含量下降 ,叶片 MDA含量增加 ,POD活性增强 ,而 SOD、CAT活性降低 ;硒可减轻镉对水稻的毒害 ,表现为 :减轻镉胁迫对株高增加的抑制 ,提高叶绿素含量 ,增加叶片干物质积累 ,提高叶片还原糖含量 (Cd0 .5 mg/ L加 Se 0 .1 0～ 0 .5 0 mg/ L例外 ) ,降低 MDA含量与 POD活性 ,提高 SOD、CAT活性     

吲哚乙酸对铝胁迫下栝楼生理响应及DNA损伤的缓解作用

为探究IAA(吲哚乙酸)对铝胁迫下栝楼生理响应及DNA损伤的缓解,本研究以河北安国栝楼(耐铝品种)和浙江浦阳栝楼(铝敏感品种)为材料进行水培试验,研究300、800 μmol·L^-1(分别用Al₃₀₀和Al₈₀₀表示)铝环境下不同浓度IAA(0、10、25、50、75 μmol·L^-1,分别以I₀、I₁₀、I₂₅、I₅₀和I₇₅表示)对2个栝楼品种的抗氧化酶活性、丙二醛(MDA)、光合特性、根系活力、叶绿素含量和DNA损伤的影响。结果表明: 与对照相比,铝胁迫条件下,安国和浦阳品种栝楼的超氧化物歧化酶(SOD)、过氧化物酶(POD)和过氧化氢酶(CAT)活性、光合作用能力、根系活力等生理指标受到不同程度的抑制,MDA含量明显升高,DNA损伤加重。铝胁迫条件下,与无IAA喷施相比,10～50 μmol·L^-1IAA作用下安国和浦阳栝楼的SOD、CAT和POD酶活性最大增幅分别为15.0%、31.2%、72.3%和13.8%、26.9%、26.4%,叶绿素含量显著增加49.9%和17.9%,MDA积累量减少39.2%和22.4%,荧光参数得到明显改善。25 μmol·L^-1IAA使安国和浦阳栝楼根系活力显著增加159.1%和90.9%,50 μmol·L^-1IAA可有效减缓2个品种栝楼根系DNA拖尾现象,尾部 DNA 百分含量与尾部距离的乘积(OTM)值最大降幅可达27.6%。10～50 μmol·L^-1 IAA能有效提升铝胁迫下栝楼的生理活性,减缓DNA损伤程度,且安国品种的耐铝胁迫能力大于浦阳品种。     

水稻根系响应镉胁迫的蛋白质差异表达

为探讨水稻根系对镉胁迫的分子生理响应,以抗镉水稻PI312777和镉敏感水稻IR24为材料,设置Cd~(2+)浓度为0、50和100μmol/L的水培试验,处理7 d后分析了水稻根系的蛋白质差异表达。结果表明,在镉胁迫下水稻PI312777和IR24根系有18个蛋白质发生了差异表达,其中的12个得到MALDI-TOF/MS鉴定。这些鉴定的蛋白功能可分四类:(1)与活性氧(ROS)胁迫相关的过氧化物酶(POD)、蛋氨酸腺苷转移酶(MAT)、类萌发素蛋白前体;(2)与谷胱甘肽(GSH)合成相关的S-腺苷甲硫氨酸合成酶(SAMS)、谷氨酰胺合成酶(GS)和谷氨酸脱氢酶(GDH);(3)与逆境胁迫相关的ABA胁迫诱导蛋白含HVA22域蛋白、ABA-胁迫-成熟诱导蛋白5(ASR5);(4)与细胞分裂调控相关的GTP结合核蛋白Ran-2。镉胁迫下SAMS和GTP结合核蛋白Ran-2在两种水稻根系均发生上调表达;MAT、POD、类萌发素蛋白前体和GS发生下调表达;依赖NADP-GDH、GDH和磷酸甘油酸变位酶在IR24根部均发生下调表达,在PI312777根部仅在100μmol/L Cd~(2+)处理发生下调表达;含HVA22域蛋白在PI312777根部上调表达,在IR24根部发生下调表达;ASR5在PI312777根部上调表达,在IR24根部的表达无显著差异;100μmol/L Cd~(2+)胁迫下60S酸性核糖体蛋白P0在水稻PI312777根部表达下调,在IR24根部表达上调。可见,镉胁迫使水稻根部ROS增加,形成氧化胁迫反应,造成毒害作用,而水稻根通过调节SAMS和GS提高GSH合成降低镉毒害。ASR5和HVA22蛋白等逆境胁迫蛋白的表达差异则是水稻品种间抗性差异的重要原因之一。     

Cd2+胁迫对石菖蒲生理生化特性的影响

通过水堵实验,研究了不同浓度(0、50、200、400μmol/L)下和不同时间内(3、7、11d)Cd2+对石菖蒲(Acorus ta-tarinowii Sehott)叶片抗氧酶活性、叶绿素含量、脂质过氧化程度以及脯氨酸含量的影响.结果表明:(1)超氧化物歧化酶(SOD)活性在3d时随着胁迫浓度的增大而增加,但7d和11d时都是在50 μmol/L浓度下达到峰值,然后降低,但都高于对照;除400μmol/L处理下SOD随胁迫时间延长呈先降后升的趋势外,其余浓度处理下均升高.(2)过氧化物酶(POD)活性在胁迫3d和7d时均随着胁迫浓度的增大而增加,11d时在200 μmol/L处理下达到峰值,然后降低;各浓度处理组均随着胁迫时间的延长POD活性呈下降趋势.(3)过氧化氢酶(CAT)活性在不同时间内随着胁迫浓度的增加呈先增后降趋势,并且各浓度处理组的CAT均随胁迫时间的延长而增加.(4)叶绿素含量在不同胁迫时间内均在200μmol/L处理下达到峰值,然后降低;除400μmol/L处理下的叶绿素随胁迫时间延长而增加外,其余浓度处理组均呈下降趋势.(5)丙二醛(MDA)含量和脯氨酸(Pro)含量均随着胁迫浓度的增加和胁迫时间的延长而增加.研究结果分析表明石菖蒲对Cd2+胁迫有一定的耐受性.     

Cadmium stress suppresses lateral root formation by interfering with the root clock

A biological clock activated by oscillating signals, known as root clock, has been linked to lateral root (LR) formation and is essential for regular LR spacing along the primary root. However, it remains unclear how this internal mechanism is influenced by environmental factors known to affect the LR pattern. Here, we report that excessive cadmium (Cd) inhibits LR formation by disrupting the lateral root cap (LRC)‐programmed cell death (PCD)‐regulated root clock. Cd restricts the frequency of the oscillating signal rather than its amplitude. This could be attributed to the inhibition on meristematic activity by Cd, which resulted in decreased LRC cell number and LRC‐PCD frequency. Genetic evidence further showed that LRC cell number is positively correlated with root resistance to Cd. Our study reveals root cap dynamics as a novel mechanism mediating root responses to Cd, providing insight into the signalling pathways of the root clock responding to environmental cues.     

镉胁迫对芥蓝根系质膜过氧化及ATPase活性的影响

水培条件下,以“香港白花”芥蓝品种为供试材料,研究4种不同浓度镉（0、1.0、2.0、4.0、8.0 mg/L Cd）处理对芥蓝幼苗根系质膜过氧化及ATPase活性的影响。结果表明,与对照相比,随着Cd处理浓度的增加,芥蓝根系活力呈现降低的变化趋势,而根系超氧化物歧化酶（SOD）、过氧化物酶（POD）和过氧化氢酶（CAT）活性以及丙二醛（MDA）、H2O2含量和O2-产生速率表现出升高的趋势,表明芥蓝受到活性氧物质的胁迫。1.0、2.0 mg/L Cd浓度处理下的H2O2含量与对照差异不显著,而O2-产生速率则在1.0 mg/L浓度处理下与对照差异不显著。随着Cd处理浓度的增加,芥蓝根系质膜H -ATPase和Ca2 -ATPase活性呈现出先增后减的变化趋势。1.0 mg/LCd浓度处理时,H -ATPase和Ca2 -ATPase活性与对照差异不显著（P > 0.05）,而在2.0、4.0和8.0 mg/LCd处理时,两种ATPase活性显著降低（P < 0.05）,并且与膜脂过氧化水平呈极显著的负相关（R2 > 0.969）。因此,低浓度Cd处理对芥蓝根系质膜两种ATPase活性影响较小,较高浓度Cd处理使芥蓝根系活力和质膜ATPase的损伤加重。     

Cadmium-induced oxalate secretion from root apex is associated with cadmium exclusion and resistance in Lycopersicon esulentum

The mechanisms of heavy metal resistance in plants can be classified into internal tolerance and exclusion mechanisms, but exclusion of heavy metals with the help of organic acids secretion has not been well documented. Here we demonstrated the contribution of oxalate secretion to cadmium (Cd) exclusion and resistance in tomato. Different Cd resistance between two tomato cultivars was evaluated by relative root elongation (RRE) and Cd accumulation. Cultivar 'Micro-Tom' showed better growth and lower Cd content in roots than 'Hezuo903' at different Cd concentrations not only in short-term hydroponic experiment but also in long-term hydroponic and soil experiments, indicating that the genotypic difference in Cd resistance is related to the exclusion of Cd from roots. 'Micro-Tom' had greater ability to secrete oxalate, suggesting that oxalate secretion might contribute to Cd resistance. Cd-induced secretion of oxalate was localized to root apex at which the majority of Cd accumulated. Phenylglyoxal, an anion-channel inhibitor, effectively blocked Cd-induced oxalate secretion and aggravated Cd toxicity while exogenous oxalate supply ameliorated Cd toxicity efficiently. These results indicated that the oxalate secreted from the root apex helps to exclude Cd from entering tomato roots, thus contributes to Cd resistance in the Cd-resistant tomato cultivar.     

Possible roles of phytochelatins and glutathione metabolism in cadmium tolerance in chickpea roots

The possible roles of phytochelatin (PC) and glutathione (GSH) in the heavy metal detoxification in plants were examined using two varieties (CSG-8962 and C-235) of chickpea (Cicer arietinum L.). The seedlings were grown for 5 days and the roots were treated with 0–20 μM CdSO₄ for 3 days. The CSG-8962 seedlings exhibited more Cd-tolerant characteristics than did the C-235, where the roots, rather than shoots, suffered from more toxic effects by Cd. Both the seedlings synthesized the large amounts of PCs and homo-phytochelatins (hPCs) in roots, but only a little in shoots in response to Cd. The Cd treatments also caused a marked increase in the levels of GSH and cysteine in both the root and shoot tissues, suggesting that Cd may activate the GSH biosynthesis and, hence, enhance PC synthesis in the plants. Such a Cd-sensitive PC synthesis in chickpea plants does not explain the difference in Cd sensitivity in the varieties, but can be used as a biochemical indicator for Cd contamination in various environments. In the chickpea plants, possible PC-dependent and independent mechanisms for Cd tolerance are discussed. Electronic Publication     

pH值和Fe、Cd处理对水稻根际及根表Fe、Cd吸附行为的影响

通过营养液-蛭石联合培养试验,设置系列pH值(4.5—7.5)和Fe、Cd处理,研究不同pH值及Fe、Cd浓度对水稻和蛭石表面Fe、Cd吸附的影响。结果表明,不同pH值处理下的根际氧化还原电位和酸度不同,0.9 mg/L Cd处理下的根际氧化势低于0.5 mg/L Cd,50 mg/L Fe处理下的根际酸度高于30 mg/L Fe处理。根表吸附Fe、Cd组分和数量都受根际Eh、pH值制约,根表Fe、Cd吸附量在处理pH值6.0时最低,并分别在处理pH值7.5和处理pH值4.5达到最高。但根系表面对Fe、Cd的吸附机制与蛭石表面不同,蛭石吸附Fe主要为晶态Fe,占到总沉积Fe的73%—87%;水稻根表沉积Fe以非晶态Fe为主,占总沉积Fe的91%—95%;与处理pH值和根际Eh间有显著的相关性(蛭石晶态Fe:ppH=0.011、pEh=0.042;水稻根表非晶态Fe:ppH=0.050、pEh=0.004)。蛭石表面交换态Fe及交换态Cd与处理pH值和Eh间存在显著的相关性(pH值:pFe<0.001、pCd=0.009;Eh:pFe=0.016、pCd=0.002),而根表交换态Fe及交换态Cd仅与处理pH值间有显著的相关性(pFe=0.007,pCd=0.048)。不同Fe、Cd浓度处理对根际Eh、pH值的升降和根表Fe、Cd吸附均有影响。与对照相比,增Cd处理可以降低根际Eh和升高pH值,减少溶液Cd浓度并增加根表Cd吸附量;增Fe处理则可以升高根际Eh和降低pH值,增加溶液Fe、Cd浓度并减少根表Fe、Cd吸附量。这是水稻应对Fe、Cd浓度胁迫的生理反应之一。     

Patterns of accumulation of selected metals in members of the soft-water macrophyte flora of central Ontario lakes

The patterns of accumulation of Ni, Cu, Zn, Pb, Cd, Fe, Mn and Al in plant species which are members of the flora of soft-water central Ontario (Canada) lakes are presented. The allocation of each metal between roots and shoots varies with the metal and the overall level of metal enrichment of the site. There is interspecific variation in metal accumulation, but the greatest differences are between vascular plants and bryophytes, rather than within these groups. An index of overall metal enrichment of each site is developed using Cu and Ni sediment concentrations. In Eriocaulon septangulare With., plant metal concentrations were uncorrelated to environmental levels of the corresponding metal but did show trends relative to the index. High plant metal concentrations did not correspond to high index levels for Zn, Mn, Cd and Al. It is suggested that in highly metal-enriched environments competitive exclusions by more common metal ions may be occurring at uptake sites within the plant. As a result of this complexity, metal accumulation in E. septangulare has no predictive value as an indicator of environmental metal contamination.     

Distribution and Toxic Effects of Cadmium and Lead on Maize Roots

Two-day-old seedlings of maize (Zea mays L.) were incubated on Cd and Pb nitrate solutions at the concentrations that inhibited root growth approximately by 50% after two-day-long incubation (LC₅₀; 10^–4 and 10^–3 M, respectively) or completely terminated growth of the primary root after one-day-long incubation (LC; 5 × 10^–4 and 10^–2 M, respectively). Cd and Pb contents were measured using an anodic inversion voltammetric technique in a flow injection system and a histochemical method. At LC₅₀, Cd and Pb were discerned, by histochemical techniques, in all root apical tissues, whereas in the root hair zone, the heavy metals were primarily accumulated in the apoplast of the rhizodermis and cortex and to a lesser extent, in the vascular tissues and parenchyma cells surrounding the metaxylem vessels. Insignificant accumulation of Cd and Pb in the pericycle probably explains why root branching was tolerant to these agents. At LC, Cd and Pb were found in the apoplast of all root tissues, in accordance with the practically complete inhibition of root growth and branching. Irrespectively of Cd and Pb concentrations in the external solution, the metal contents in the root apex exceeded those in the basal region. Procion dyes were used to assess cell death inflicted by Cd and Pb. At LC, the root cap and meristematic cells perished, together with the rhizodermal cells and the outer cortical cells of the root apex, whereas only the rhizodermal cells in the root apical region died at LC₅₀. The evidence that Cd and Pb cross the endodermal barrier at LC presumes that, at lower metal concentrations, the Casparian strip and plasmalemma of the endodermis regulate the transport of these metals into the central cylinder. The authors conclude that the identical barriers control Cd and Pb transport in root tissues.     

Soil pH Effects on Uptake of Cd and Zn by Thlaspi caerulescens

For phytoextraction to be successful and viable in environmental remediation, strategies that can optimize plant uptake must be identified. Thlaspi caerulescens is an important hyperaccumulator of Cd and Zn, whether adjusting soil pH is an efficient way to enhance metal uptake by T. caerulescens must by clarified. This study used two soils differing in levels of Cd and Zn, which were adjusted to six different pH levels. Thlaspi caerulescens tissue metal concentrations and 0.1 M Sr(NO₃)₂ extractable soil metal concentrations were measured. The soluble metal form of both Cd and Zn was greatly increased with decreasing pH. Lowering pH significantly influenced plant metal uptake. For the high metal soil, highest plant biomass was at the lowest soil pH (4.74). The highest shoot metal concentration was at the second lowest pH (5.27). For low metal soil, due to low pH induced Al and Mn toxicity, both plant growth and metal uptake was greatest at intermediate pH levels. The extraordinary Cd phytoextraction ability of T. caerulescens was further demonstrated in this experiment. In the optimum pH treatments, Thlaspi caerulescens extracted 40% and 36% of total Cd in the low and high metal soils, respectively, with just one planting. Overall, decreasing pH is an effective strategy to enhance phytoextraction. But different soils had various responses to acidification treatment and a different optimum pH may exist. This pH should be identified to avoid unnecessarily extreme acidification of soils.     

Phytotoxic Effects of Cd, Zn, Pb, Cu and Fe on Sinapis Alba L. Seedlings and their Accumulation in Roots and Shoots

The inhibitory effects of Cd, Cu, Zn, Pb, and Fe on root elongation, contents of photosynthetic pigments, and metal accumulation in the roots and shoots of Sinapis alba were assessed. On the basis of growth inhibition metals can be arranged in a order Cu > Cd > Fe = Zn > Pb. All the metals, except Fe, were accumulated in significantly higher amount in the roots than in the shoots. Cd, Zn, Cu and Pb reduced chlorophyll a, and especially chlorophyll b content, and Zn and Pb reduced the carotenoid content, but less than that of chlorophyll a+b. The plants contained the highest concentration of Cd, and the lowest concentration of Zn.