Variation in cadmium accumulation and translocation among peanut cultivars as affected by iron deficiency

Purpose

The current study aimed to test the hypothesis that the variations in shoot Cd accumulation among peanut cultivars was ascribed to the difference in capacity of competition with Fe transport, xylem loading and transpiration.

Methods

A hydroponics experiment was conducted to determine the plant biomass, gas exchange, and Cd accumulation in Fe-sufficient or -deficient plants of 12 peanut cultivars, at low Cd level (0.2 μM CdCl₂).

Results

Peanut varied among cultivars in morpho-physiological response to Cd stress as well as Cd accumulation, translocation and distribution. Qishan 208 and Xvhua 13 showed a higher capacity for accumulating Cd in their shoots. Fe deficiency increased the concentration and amount of Cd in plant organs, but decreased TF _{root to shoot} and TF _{root to stem}, while TF _{stem to leaf} remained unaffected. Fe deficiency-induced increase rates of Cd concentration and total Cd amount in roots and leaves were negatively correlated with the values in Fe-sufficient plants. Transpiration rate was positively correlated with leaf Cd concentration, TF _{root to shoot}, TF _{root to stem} and TF _{stem to leaf}.

Conclusions

The difference in shoot Cd concentration among peanut cultivars was mainly ascribed to the difference in Fe transport system, xylem loading capacity and transpiration.     

Peanut as a potential crop for bioenergy production via Cd-phytoextraction: A life-cycle pot experiment

Aims

The current study aimed to assess the potential of peanut (Arachis hypogaea L.) for bioenergy production via phytoextraction in cadmium (Cd) -contaminated soils and screen appropriate cultivars for this approach.

Methods

A life-cycle pot experiment was conducted to determine the biomass, seed yield, oil content and Cd accumulation of seven peanut cultivars under Cd concentration gradients of 0, 2, and 4 mg kg^?1.

Results

Peanut exhibits genotypic variations in Cd tolerance, seed production, oil content, and Cd accumulation. Exposure of plants to 2 and 4 mg kg^?1 Cd did not inhibit shoot biomass, seed yield, and oil content for most of the cultivars tested. There are large amounts of Cd accumulated in the shoots. Although the seed Cd concentration of peanut was relatively high, the Cd concentration in seed oils was very low (0.04-0.08 mg kg^?1). Among the cultivars, Qishan 208 showed significant Cd tolerance, high shoot biomass, high pod and seed yield, high seed oil content, considerable shoot Cd concentration, and the largest translocation factor and total Cd in shoots.

Conclusions

The cultivation of peanut in Cd-contaminated farmland was confirmed to be feasible for bioenergy production via phytoextraction, and Qishan 208 is a good candidate for this approach.     

Characterization of cadmium concentration and translocation among ramie cultivars as affected by zinc and iron deficiency

Zn and Fe are essential nutritional elements in plants and play important roles in various physiological processes of plants. Zn and Fe are chemically similar to cadmium (Cd); therefore, Zn and Fe may mediate Cd-induced physiological or metabolic changes in plants. In order to evaluate the interaction between Cd, Zn and Fe, we conducted a hydroponics experiment to determine the plant biomass, photosynthetic characteristics, and Cd accumulation of ten ramie cultivars under Zn/Fe-sufficient or Zn/Fe-deficient conditions in the presence of 32 µM CdCl₂. Ramie varied among cultivars in morpho-physiological response to Cd stress as well as Cd accumulation, translocation and distribution. Zn and Fe deficiency increased the concentration and amount of Cd in plant organs, but decreased TF_{stem to leaf} and TF_{root to stem}. Cultivars with more Cd in roots and shoots showed smaller increase in Cd accumulation under Zn and Fe-deficiency stress. Xiangzhu 7 and Duobeiti 1 showed a higher capacity of Cd accumulation in their shoots. Zn and Fe deficiency decreased Pn, but increased Ci, Gs, and E in most cultivars. The difference in Cd translocation among ramie cultivars was mainly ascribed to the difference in plant transpiration.     

Effects of rhizosphere oxygen concentration on root physiological characteristics and anatomical structure at the tillering stage of rice

Oxygen is essential for all aerobic organisms. Higher plants need oxygen to sustain metabolism and growth. After experiencing anaerobic stress for a period of time, most plant tissues will be damaged. This study examined the physiological characteristics and anatomical structures in the root tips of rice seedlings (cultivars Xiushui09 and Chunyou84) in response to different rhizosphere oxygen environments. The results showed that moderate oxygen (MO: 2.5–3.5 mg L⁻¹) increased the dry weight accumulation and formation of rice roots (including length, surface area, number of tips) in both genotypes. Compared to under normal conditions (NC), the magnitudes of increase in these four variables were 4.67, 66.40, 35.44 and 49.50% in Xiushui09 and 12.25, 15.59, 13.57 and 13.48% in Chunyou84, respectively. Low oxygen (LO: 0–1.0 mg L⁻¹) stress decreased the root surface area but increased root volume and average diameter. LO and high oxygen (HO: >6.8 ± 0.21 mg L⁻¹) stress each damaged the apical cells' ultrastructure, reduced the number of organelles, and increased electrical conductivity. Meanwhile, the root activity and respiration of rice seedlings decreased; the abscisic acid content increased compared to levels under NC. Under MO treatment, the cell membrane was not damaged, the root tip organelles were rich, the soluble protein content, root activity, respiration rate and gibberellic acid content increased compared to levels under NC; the magnitudes of these increases were 24.76, 36.00, 8.00 and 283.00% in Xiushui09 and 4.78, 40.00, 15.45 and 49.35% in Chunyou84, respectively. In conclusion, MO optimised rice root morphology and enhanced root physiological activity.     

不同抗旱性花生品种结荚期叶片生理特性

以12个花生品种为试验材料,在人工控水条件下,于结荚期设置0~80 cm土层相对含水量为70%和50% 2个处理,研究与花生抗旱性相关的叶片生理生化性状及不同品种抗旱的叶片机制.结果表明： 利用产量抗旱系数可将12个花生品种的抗旱性分为强、中、弱3级,抗旱性强的品种有A596、山花11号、如皋西洋生,中度抗旱品种有花育20、农大818、海花1号、山花9号和79266,抗旱性弱的品种有ICG6848、白沙1016、花17和蓬莱一窝猴.A596、山花11号、如皋西洋生的抗旱机制是具有较强的叶片抗氧化保护能力、较高的PSⅡ活性及光合速率(P_n).海花1号的叶片抗氧化保护能力较强,山花9号的PSⅡ活性有显著优势.相关分析表明,叶片P_n、气孔限制值(L_s)、最大光化学效率(F_v/F_m)、光化学猝灭系数(q_P)、丙二醛(MDA)含量、相对电导率和超氧化物歧化酶(SOD)活性与花生品种的抗旱系数有显著的相关性,是花生结荚期的重要抗旱性状.SOD活性的抗旱级别需在干旱胁迫下鉴定,其他性状可在正常灌水条件下鉴定.山花11号和79266可分别作为花生强、弱抗旱性鉴定的标准品种,山花11号可作为花生叶片优异抗旱性状鉴定的标准品种.     

不同镉水平下大麦幼苗生长和镉及养分吸收的品种间差异

利用水培试验研究了不同Cd水平下大麦幼苗的Cd和几种矿质元素吸收、积累、生长和生物学产量的品种间差异 .结果表明 ,1μmol·L-1Cd处理显著降低麦苗株高、绿叶数、叶绿素计读数、地上部和根系干重 ,显著抑制植株对Zn、Mn、Cu的吸收和累积 ;品种之间存在着显著差异 ,无芒六棱受抑制最为严重 ,米麦 114和浙农 1号表现出相对较强的抗性 .麦苗Cd含量和累积量品种之间也有显著差异 ,浙农 1号的Cd含量最高 ,米麦 114最低 .相关分析表明 ,麦苗生物学产量与地上部Cd含量、累积量及根系Cd含量呈显著负相关 ,其中与地上部Cd含量的相关性最强 ,与根系Cd累积量无显著相关 .     

Wide vessels sustain marginal transpiration flux and do not optimize inefficient gas exchange activity under impaired hydraulic control and salinity

Plants optimize water use and carbon assimilation via transient regulation of stomata resistance and by limiting hydraulic conductivity in a long-term response of xylem anatomy. We postulated that without effective hydraulic regulation plants would permanently restrain water loss and photosynthetic productivity under salt stress conditions. We compared wild-type tomatoes to a transgenic type (TT) with impaired stomatal control. Gas exchange activity, biomass, starch content, leaf area and root traits, mineral composition and main stems xylem anatomy and hydraulic conductivity were analyzed in plants exposed to salinities of 1 and 4 dS m⁻¹ over 60 days. As the xylem cannot easily readjust to different environmental conditions, shifts in its anatomy and the permanent effect on plant hydraulic conductivity kept transpiration at lower levels under unstressed conditions and maintained it under salt-stress, while sustaining higher but inefficient assimilation rates, leading to starch accumulation and decreased plant biomass, leaf and root area and root length. Narrow conduits in unstressed TT plants were related to permanent restrain of hydraulic conductivity and plant transpiration. Under salinity, TT plants followed the atmospheric water demand, sustained similar transpiration rate from unstressed to salt-stressed conditions and possibly maintained hydraulic integrity, due to likely impaired hydraulic regulation, wider conduits and higher hydraulic conductivity. The accumulation of salts and starch in the TT plants was a strong evidence of salinity tolerance via osmotic regulation, also thought to help to maintain the assimilation rates and transpiration flux under salinity, although it was not translated into higher growth.     

丛枝菌根真菌对砂培玉米幼苗根系特征、光合生理与镉累积的影响

【背景】丛枝菌根真菌(arbuscular mycorrhizal fungi,AMF)是一类重要的土壤微生物,能显著影响植物对镉(cadmium,Cd)的耐性与累积,但其对不同形态Cd胁迫的响应尚不清楚。【目的】探讨不同形态Cd胁迫下接种AMF对玉米(Zea mays L.)生长和Cd累积的影响。【方法】采用30 cm高的培养容器填装石英砂(0.2 mm),开展室内砂培玉米试验,研究溶解态和胶体态Cd (1 mg/kg)胁迫下,接种摩西斗管囊霉(Funneliformis mosseae)对玉米幼苗生长、根系特征、光合生理及Cd累积的影响。【结果】双因素分析表明,AMF和Cd形态均对玉米生长(株高和生物量)、根系特征、光合生理(叶绿素含量和光合速率)与Cd累积量存在显著的影响,但二者之间没有显著交互作用。与未接种处理相比,接种AMF显著降低玉米株高、生物量、叶片叶绿素含量和光合速率,抑制玉米根长、根表面积、根体积和根尖数;同时增加了玉米根系Cd含量,但减少玉米地上部Cd含量以及地上部与根系Cd累积量;与胶体态Cd处理相比,溶解态Cd显著降低玉米的根长、根表面积、平均根系直径、根尖数和地上部Cd累积量,但增加了植株叶片光合速率、根系Cd含量和累积量。相关分析发现,玉米根长、根表面积和根尖数与地上部Cd含量呈显著或极显著正相关,与根系Cd含量呈极显著负相关。【结论】溶解态Cd比胶体态Cd对砂培玉米幼苗的毒害效应严重,而且接种AMF加重溶解态和胶体态Cd对玉米幼苗的损伤,但降低了植株对Cd的累积。     

德国鸢尾对Cd胁迫的生理生态响应及积累特性

通过盆栽研究了Cd胁迫下德国鸢尾的生长状况、生态效应、生理特性及吸收和富集Cd的能力.结果表明:德国鸢尾对小于5 mg/kg的Cd有较强的耐性,适用于城区土壤修复;Cd浓度大于5 mg/kg时抑制德国鸢尾生长,降低了其生态效应.随着Cd浓度的增大,德国鸢尾根系活力、叶绿素含量和含水量逐渐降低,游离脯氨酸和可溶性糖含量先升高后降低,细胞膜透性逐渐升高.Cd在德国鸢尾体内分布为根系＞地上部分,随着Cd浓度的增大,德国鸢尾根系和地上部分Cd积累浓度逐渐升高、富集系数和转运系数逐渐降低;Cd浓度为20 mg/kg时德国鸢尾对Cd的积累量最大,为2.122 mg/plant.     

Root Respiration,Photosynthesis and Grain Yield of Two Spring Wheat in Response to Soil Drying

The effects of soil water regime and wheat cultivar, differing in drought tolerance with respect to root respiration and grain yield, were investigated in a greenhouse experiment. Two spring wheat (Triticum aestivum) cultivars, a drought sensitive (Longchun 8139-2) and drought tolerant (Dingxi 24) were grown in PVC tubes (120 cm in length and 10 cm in diameter) under an automatic rain-shelter. Plants were subjected to three soil moisture regimes: (1) well-watered control (85% field water capacity, FWC); (2) moderate drought stress (50% FWC) and (3) severe drought stress (30% FWC). The aim was to study the influence of root respiration on grain yield under soil drying conditions. In the experiment, severe drought stress significantly (p < 0.05) reduced shoot and root biomass, photosynthesis and root respiration rate for both cultivars, but the extent of the decreases was greater for Dingxi 24 compared to that for Longchun 8139-2. Compared with Dingxi 24, 0.04 and 0.07 mg glucose m⁻² s⁻¹ of additional energy, equivalent to 0.78 and 1.43 J m⁻² s⁻¹, was used for water absorption by Longchun 8139-2 under moderate and severe drought stress, respectively. Although the grain yield of both cultivars decreased with declining soil moisture, loss was greater in Longchun 8139-2 than in Dingxi 24, especially under severe drought stress. The drought tolerance cultivar (Dingxi 24), had a higher biomass and metabolic activity under severe drought stress compared to the sensitive cultivar (Longchun 8139-2), which resulted in further limitation of grain yield. Results show that root respiration, carbohydrates allocation (root:shoot ratio) and grain yield were closely related to soil water status and wheat cultivar. Reductions in root respiration and root biomass under severe soil drying can improve drought tolerant wheat growth and physiological activity during soil drying and improve grain yield, and hence should be advantageous over a drought sensitive cultivar in arid regions.     

Morpho-physiological responses of sugar beet (Beta vulgaris L.) genotypes to drought stress

The identification of morpho-physiological traits related to drought tolerance and high yield potential is a challenge when selecting sugar beet genotypes with greater tolerance to water stress. In this paper, root morphological parameters, antioxidant systems, leaf relative water content (RWC) and H⁺-ATPase activity as key morpho-physiological traits involved in drought tolerance/susceptibility of sugar beet were studied. Genotypes showing a different drought tolerance index (DTI) but a similar yield potential, under moderate (?0.6 Mpa) and severe (?1.2 MPa) water stress, were selected and their morpho-physiological traits were investigated. The results showed a wide genetic variation in morpho-physiological parameters which demonstrated the different adaptive strategies under moderate and severe drought conditions in sugar beet. In particular, an efficient antioxidant system and redox signalling made some sugar beet genotypes more tolerant to drought stress. The alternative strategy of other genotypes was the reduction of root tissue density, which produced a less dense root system improving the axial hydraulic conductivity. These results could be considered as interesting challenge for a better understanding of the drought tolerance mechanisms in sugar beet.     

Low-molecular-weight organic acids in rhizosphere soils of durum wheat and their effect on cadmium bioaccumulation

Cadmium (Cd) accumulation has been found to vary between cultivars of durum wheat (Triticum turgidum var. durum), and it is hypothesized that low-molecular-weight organic acids (LMWOAs) produced at the soil-root interface (rhizosphere) may play an important role in the availability and uptake of Cd by these plants. The objective of this study, therefore, was to (1) investigate the nature and quantity of LMWOAs present in the rhizosphere of durum wheat cultivars Arcola (low Cd accumulator) and Kyle (high Cd accumulator) grown in three different soils: Yorkton, Sutherland and Waitville, and (2) determine the relationship between Cd accumulation in these plants and LMWOAs present in the rhizosphere. Plants were grown for two weeks in pot-cultures under growth chamber conditions. Oxalic, fumaric, succinic, L-malic, tartaric, citric, acetic, propionic and butyric acids were found and quantified in the water extracts of rhizosphere soil, with acetic and succinic acids being predominant. No water extractable LMWOAs were identified in the bulk soil. Total amount of LMWOAs in the rhizosphere soil of the high Cd accumulator (Kyle) was significantly higher than that for the low Cd accumulator (Arcola) in all three soils. Furthermore, large differences in amounts of LMWOAs were found in the rhizosphere soil for the same cultivars grown in different soils and followed the pattern: Sutherland > Waitville > Yorkton. Extractable soil Cd (M NH4Cl) and Cd accumulation in the plants also followed the same soil sequence as LMWOA production. Cadmium accumulation by the high and low Cd accumulating cultivars was proportional to the levels of LMWOAs found in the rhizosphere soil of each cultivar. These results suggest that the differing levels of LMWOAs present in the rhizosphere soil played an important role in the solubilization of particulate-bound Cd into soil solution and its subsequent phytoaccumulation by the high and low Cd accumulating cultivars.     

Depletion of extracellular calcium increases cadmium toxicity in barley root tip via enhanced Cd uptake-mediated superoxide generation and cell death

Whereas severe Cd stress (150 µM Cd) causes root growth arrest as a consequence of marked superoxide generation leading to extensive cell death in the root tips, mild Cd stress (15 µM Cd) evokes morphogenic responses, such as reduced root elongation and radial root expansion, resulting in shorter and thicker roots. Similar to the low Cd concentration-caused mild stress, treatment of roots with either Ba to remove exchangeable or EDTA to remove both exchangeable and tightly bound cations, including Ca and Mg, from the apoplast, induced root growth inhibition and swelling. However, pre-treatment of roots with Ba had a synergistic effect on the development of these mild Cd stress-induced morphogenic responses, but without the development of any other symptoms in the root tips. In turn, EDTA pre-treatment markedly increased the toxicity of Cd in barley root tips via enhanced Cd uptake-mediated superoxide generation, which evoked extensive cell death in the transition zone of root tips identically to the high Cd concentration-induced severe stress. While the mild stress-induced responses were alleviated by the inhibition of auxin signalling pathway, the severe stress-induced symptoms were prevented by Ca, but not Mg, supplementation or by the inhibition of Cd uptake into the root symplasm. Therefore, the appropriate concentration of Ca in the apoplast is crucial to prevent the rapid accumulation of Cd in the symplasm, which above a certain threshold level leads to the huge superoxide generation and cell death.     

不同性别桑树幼苗对镉与酸雨复合处理的生长响应及镉积累差异

为研究不同性别桑树在镉(Cd)与酸雨(AR)复合处理条件下的生长与镉积累差异,本试验以‘强桑1号’(雌株)和‘农桑14号’(雄株)两种不同性别桑树为材料,研究重金属镉(100 mg·kg^-1干土)和模拟酸雨(pH 3.0)处理下,两者生物量积累和分配、最大净光合速率(A_max)和叶绿素荧光参数,以及Cd积累与分配的差异.试验共设置无Cd和AR(对照)、单独Cd、单独AR、Cd+AR复合4个处理.结果表明:单独Cd处理虽然显著增加了雌株和雄株根茎叶中Cd含量,而且雌株各部分Cd含量显著高于雄株,但是只有雄株根、茎和总生物量、最大净光合速率显著下降,而雌株除了A_max显著下降外,各部分生物量积累下降均不显著,且两者的最大光化学效率(F_v/F_m)、光化学淬灭系数(q_P)和非光化学淬灭系数(q_N)均未发生显著变化.复合处理下,雄株和雌株的总生物量、A_max均显著降低,与单独镉处理相比,雌株根和叶中的Cd含量显著升高,但雄株没有明显变化,两者的F_v/F_m、q_P没有显著变化,但q_N均显著降低.短时间处理下桑树雌株对单独镉胁迫的耐受性高于雄株,但是酸雨的加入会降低雌株对镉的耐受性,可能是因为酸雨促进雌株根系对镉的吸收,并导致叶片积累了更多的镉.     

胡杨木质部水分传导对盐胁迫的响应与适应北大核心CSCD

解析植物木质部导水率对逆境的响应和适应对促进植物抗逆性机理研究和受损植被恢复具有重要意义。该文以荒漠河岸林建群种胡杨(Populus euphratica)为研究对象,系统分析了胡杨幼株根、茎、叶水分传输通道对不同浓度盐胁迫的响应和适应。结果表明:(1)胡杨幼株根系对盐胁迫的敏感性高于茎和叶,盐胁迫下根系生长和根尖数显著受到抑制,根木质部易于发生栓塞,导水率明显降低。(2)胡杨幼株茎木质部导水率对盐胁迫的响应依盐浓度而定,轻度(0.05 mol·L–1 Na Cl)和中度(0.15 mol·L–1 Na Cl)盐胁迫下,胡杨可以通过协调导管输水的有效性和安全性来调节木质部的导水率,维持植物正常生长;重度(0.30 mol·L–1 Na Cl)盐胁迫下,胡杨茎木质部导管输水有效性和安全性均明显降低,木质部导水率显著下降,并伴随叶片气孔导度的显著降低,从而严重抑制了胡杨的光合和生长。     

Cd胁迫下苎麻的生长响应与富集、转运特征研究

通过盆栽试验,分析了苎麻湘苎三号在Cd胁迫下生长响应及其富集、耐性和迁移特征.结果表明,低浓度Cd处理(≤100mgmg·kg^-1)能促进苎麻生长发育,株高、茎粗、有效分蘖数和生物量都有所增加,以50mg·kg^-1胁迫处理最佳;此后则随处理浓度增加抑制效应越明显,到500mg·kg^-1时,各营养生长指标较对照显著减少,但仍生长较好,表明苎麻对重金属Cd胁迫具有很强的耐性.地下部与地上部Cd含量随处理浓度提高而增加,至500 mg.k g-1浓度时达最高值,分别为221.95mg.kg-1和390.61mg·kg^-1.苎麻Cd富集系数和转运系数分别为0.47～1.10和0.57～0.94.因此,苎麻不属于Cd超富集植物,而只是Cd富集植物,鉴于其具有根系发达、保水固土能力强和地上部生物量大等特点,苎麻是目前重金属Cd污染修复较理想的植物.     

Effect of fertilizers on Cd uptake of Amaranthus hypochondriacus, a high biomass, fast growing and easily cultivated potential Cd hyperaccumulator

In a greenhouse pot experiment, we assessed the phytoextraction potential for Cd of three amaranth cultivars (Amaranthus hypochondriacus L. Cvs. K112, R104, and K472) and the effect of application of N, NP, and NPK fertilizer on Cd uptake of the three cultivars from soil contaminated with 5 mg kg(-1) Cd. All three amaranth cultivars had high levels of Cd concentration in their tissues, which ranged from 95.1 to 179.1 mg kg(-1) in leaves, 58.9 to 95.4 mg kg(-1) in stems, and 62.4 to 107.2 mg kg(-1) in roots, resulting in average bioaccumulation factors ranging from 17.7 to 29.7. Application of N, NP, or NPK fertilizers usually increased Cd content in leaves but decreased Cd content in stem and root. Fertilizers of N or NP combined did not substantially increase dry biomass of the 3 cultivars, leading to a limited increment of Cd accumulation. NPK fertilizer greatly increased dry biomass, by a factor of 2.7-3.8, resulting in a large increment of Cd accumulation. Amaranth cultivars (K112, R104, and K472) have great potential in phytoextraction of Cd contaminated soil. They have the merits of high Cd content in tissues, high biomass, easy cultivation and little effect on Cd uptake by fertilization.     

CO2浓度倍增对红松幼苗根尖和叶解剖结构及生理功能的影响

大气CO₂浓度升高对植物的影响是目前植物生态学研究中普遍关注的问题。以往的研究主要关注植物地上部分叶解剖结构及生理功能的改变, 而对根解剖结构和生理功能变化以及根与叶变化之间潜在联系的研究较少。该文以三年生红松(Pinus koraiensis)幼苗为研究对象, 通过CO₂浓度倍增(从350 µmol·mol^-1增加到700 µmol·mol^-1)试验, 研究当年生针叶和根尖解剖结构及生理功能的变化。结果表明: (1) CO₂浓度倍增处理的红松幼苗, 气孔密度显著降低, 叶肉组织面积、木质部及韧皮部面积明显增加; (2) CO₂浓度倍增导致红松幼苗根尖直径增粗, 皮层厚度和层数显著增加, 管胞直径变小; (3)高CO₂浓度处理下, 叶气孔导度和蒸腾速率降低, 光合速率和水分利用效率提高, 同时根尖的导水率显著下降, 但管胞的抗栓塞能力显著提高。这些结果显示, 叶和根解剖结构及生理功能在CO₂浓度升高条件下具有一致的响应。未来研究中应该同时关注全球气候变化对植物地上和地下器官结构与功能的影响。     

Root adaptations to cadmium-induced oxidative stress contribute to Cd tolerance in the hyperaccumulator Sedum alfredii

Short-term responses of Sedum alfredii roots to Cd exposure was compared in Cd hyperaccumulator (HE) and nonhyperaccumulating ecotype (NHE). Cadmium exposure significantly inhibited root elongation and induced loss of plasma membrane integrity and lipid peroxidation of roots tips in the NHE, whereas these effects were much less pronounced in the HE plants. A strong accumulation of reactive oxygen species with increasing Cd concentration was noted in the NHE root tips, but not in HE. After Cd exposure, a dose-dependent decrease in oxidized glutathione and marked increase in reduced glutathione and non-protein thiols were observed in root tips of HE, but were not seen in the NHE plants. These results suggest that the HE tolerates high Cd in the environment through the differential adaptations against Cd-induced oxidative stress.