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Background and aims Sedum alfredii is a recently identified cadmium (Cd) hyperaccumulator of increasing interest for its potential use in phytoextraction. In this study, we examined short-term responses of roots of the Cd hyperaccumulating ecotype (HE) S. alfredii to Cd exposure with comparison with its non-hyperaccumulating ecotype (NHE). The toxic trace pollutant cadmium (Cd) enters the environment mainly from industrial processes and phosphate fertilizers (Wagner, 1993), and is damaging to plant, animal and human health (Bertina and Averbeck, 2006). In plants, a few micromoles of Cd in the root environment is toxic resulting in root tip damage, reduced photosynthesis, induced antioxidant responses in all plant organs, and growth inhibition (Das et al., 1998). Cadmium is assumed to cause the direct or indirect formation of reactive oxygen species (ROS) in plants (Rodríguez-Serrano et al., 2006), and to interfere with the redox status of cells (Sandalio et al., 2001; Schützendübel et al., 2001; Bertina and Averbeck, 2006). In most plants, visible effects of exposure to high Cd doses are growth inhibition and leaf chlorosis (Das et al., 1998). In some plant species including Thlaspi caerulescens (Boominathan and Doran, 2003) and Brassica juncea (Pilon-Smits et al., 2000), Cd can accumulate to substantial concentrations without any toxic effects. The tolerance of Cd by these species involves a complex network of homeostatic mechanisms that control the uptake, accumulation, trafficking, and detoxification of metals (Das et al., 1998; Clemens, 2001). Once uptake and translocation of Cd have occurred, a number of mechanisms are involved that regulate the concentrations of free Cd ions among different plant organelles and hence minimize the damage to metabolism from exposure to excess Cd (Clemens, 2001; Hall, 2002). Compartmentations to vacuoles and cell walls (Bidwell et al., 2004; Krämer et al., 2000), and chelation with agents (Krämer et al., 1996; Salt et al., 1999; Ueno et al., 2005) have been suggested to play a dominant role in metal detoxification by hyperaccumulators (Clemens, 2001). Metal detoxification, however, is frequently incomplete and mechanisms that protect metabolism from metal-induced oxidative damage are necessarily involved (Boominathan and Doran, 2002; 2003; Freeman et al., 2004). The non-protein thiol (NPT), glutathione (GSH) has been suggested to play an important role in detoxification of heavy metals in plants (Han et al., 2008). GSH-mediated Ni tolerance has been previously observed in Thlaspi hyperaccumulators (Freenman et al., 2004), and Cd tolerance/accumulation was reported to be associated with GSH biosynthesis in the accumulator plant Brassica juncea (Zhu et al., 1999a; 1999b; Pilon-Smits et al., 2000). Sedum alfredii is a recently identified Cd hyperaccumulators (Yang et al., 2004), of increasing interest (Li et al., 2007) for its potential use in phytoextraction. Plants of the hyperaccumulating ecotype (HE) of S. alfredii grow natrually in a Pb/Zn area, where Cd concentration is up to 400 mg kg-1 soil. Yang et al. (2004) reported that this ecotype of S. alfredii grew healthy at Cd levels of up to 200 µM hydroponicly, whereas its contrasting ecotype (the nonhyperaccumulating ecotype, NHE) can not survive at 50 µM (Xiong et al., 2005). Like other hyperaccumulators, Sedum alfredii has an enhanced ability to translocate most of absorbed Cd from roots to shoots (Lu et al., 2008), to protect the roots from toxicity of excess metals. However, roots themselves must also possess an extraordinary ability to tolerate Cd, as in most environmental conditions the toxic metal enters the roots first. Roots of the Cd hyperaccumulator, Thlaspi caerulescens (Nedelkoska and Doran, 2000), have been suggested to possess mechanisms for enhanced metal tolerance independent of the shoots, and antioxidative metabolism might play an important role in countering the toxic effects of Cd in hairy roots of T. caerulescens (Boominathan and Doran, 2003). Previous studies on the hyperaccumulator S. alfredii indicated that there was no relationship between antioxidative defense mechanisms namely superoxide dismutase, catalase, guaiacol peroxidase, ascorbate peroxidase and glutathione reductase activities as well as ascorbic acid contents, and Cd tolerance in both roots and leaves of S. alfredii (Jin et al., 2008a). The studies by Jin et al., (2008a), however, did not provide a clear explanation for the apparent ability of roots to tolerate high cellular Cd levels. Roots tip, which comprises meristem, elongation and differentiation cells within a short distance (Scheres et al., 2002), is a very active zone of metabolism, and extremely sensitive to biotic or abiotic stress. Therefore, a precise determination for antioxidative capacity of the root tips is necessary to better understand the tolerance mechanism of HE S. alfredii in the early response to Cd. |
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4楼2009-09-19 11:02:19
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qingfeng877680(金币-3,VIP+0):机器翻译请注明，请不要简单的拿软件翻译的东西来充数。 9-19 09:01
qingfeng877680(金币-3,VIP+0):机器翻译请注明，请不要简单的拿软件翻译的东西来充数。 9-19 09:01
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背景和目的Sedum alfredii是近年来确定hyperaccumulator镉污染的日益浓厚的兴趣phytoextraction对其潜在的使用。在本研究中,我们对短期的反应的Cd hyperaccumulating根生态型(他). alfredii Cd相比,在其non-hyperaccumulating暴露与生态(新人道教育)。 有毒的痕迹的镉污染环境的主要由工业进入过程和磷酸盐化肥(瓦格纳,1993),并对植物、动物和人类的健康(Bertina和Averbeck,2006)。在植物中,几micromoles光盘的根目录下的环境是有毒的,导致伤害减少根尖诱导抗氧化反应在光合作用,所有的植物器官、生长抑素(这等,1998)。镉被认为导致直接或间接的生成活性氧(成分)在植物(Rodriguez-Serrano等,2006年)、干扰了还原状况的细胞(Sandalio等,2001;Schutzendubel等,2001;Bertina和Averbeck,2006)。在大多数植物的影响,可见暴露于高剂量和树叶绿生长抑素(这等,1998)。 在某些植物物种包括Thlaspi caerulescens(Boominathan和Doran》,2003)、甘蓝类白菜,Pilon-Smits(2000)、光盘可以积累,没有任何实质性的浓度的毒性作用。误差由这些物种包括Cd的复杂的网络止血机制的吸收、积累、贩卖、解毒的金属(这等,1998;克莱门斯,2001年)。一旦吸收、运输的Cd,涉及大量的机制,规范的Cd离子浓度的自由,因此在不同植物器官损害最小化过度暴露在新陈代谢的Cd(克莱门斯杂志,2001;大厅,2002年)。Compartmentations去泡、细胞壁(Bidwell等,2004;Krä倍,2000年,与代理商和螯);(Krä倍,1996;盐等,1999;上野等,2005)已经建议中扮演了重要的角色(火箭以金属解毒针对,2001)。金属排毒,然而,常常是完整和治疗由金属引起的机制,以保护代谢的氧化损伤是由Doran钩沉,2002(Boominathan;2003年和2004年;弗里曼:《)。这个non-protein硫醇(NPT),谷胱甘肽(GSH)已经提议中扮演重要角色的重金属在植物毒(汉等,2008年)。GSH-mediated镍宽容曾经被观察到的Thlaspi(Freenman等,针对2004年),和Cd宽容/积累被报道在合成谷胱甘肽在相关的蓄电池工厂芸薹属白菜(朱等,1999a;1999b。Pilon-Smits等,2000年)。 Sedum alfredii是针对最近鉴定Cd(阳等,2004年),越来越多的兴趣(李等,2007年)对其潜在phytoextraction使用。植物的生态(他)的hyperaccumulating alfredii natrually生长在马基效果,那里的Cd浓度达到400毫克kg-1土壤。杨等。报道说,这(2004). alfredii生态健康水平的增长在Cd上200 µ,而它hydroponicly;对比了nonhyperaccumulating生态、生态(新人道教育)不能生存在50 µ米(雄等,2005)。就像其他alfredii,Sedum针对具有增强的能力可能促使大多数吸收Cd从根芽(陆等,2008年),以保护根毒性过剩的金属。然而,自己也必须具备一根的超凡能力,像在多数容忍Cd环境中的有毒金属进入了根。hyperaccumulator激光唱碟的根源,Thlaspi caerulescens(Nedelkoska和Doran,2000),已经被认为拥有机制以增强金属宽容独立的嫩枝、和抗氧化代谢可以发挥重要的作用,在对抗毒性的作用更强的毛状根的Cd caerulescens(Boominathan和Doran》,2003)。先前的研究表明,hyperaccumulator alfredii .没有关系即抗氧化防御机制,guaiacol超氧化物歧化酶、过氧化物酶、过氧化氢酶和ascorbate还原谷胱甘肽活动以及抗坏血酸含量、Cd两根,叶宽容的s . alfredii(金等,2008a)。这项研究的金等,(2008a),然而,不提供一个明确的解释能力的根容忍明显较高水平。细胞Cd -小费,包括分根、伸长率和分化细胞在很短的距离(Scheres等,2002年),是一个非常活跃的区域的新陈代谢,极其敏感的生物或非生物的压力。因此,一个精确测定为抗氧化能力的秘诀是必要的根源的耐受机制的更好的理解alfredii .他早在回应的Cd。 |
2楼2009-09-18 09:41:24
3楼2009-09-19 09:31:54