Cd胁迫下杂交水稻对Cd的吸收及其动态变化

镉（Cd）是非必需的有毒元素,是农业环境和农产品的重要污染物,易被水稻吸收并在籽粒中积累。不同水稻品种拥有不同的独特基因,导致水稻籽粒吸收积累Cd的能力存在一定的差异。因此,开展不同水稻品种耐Cd特性及其不同生育期的吸收转运效率研究具有重要意义。本文采用水培试验,研究了两个水稻（Oryza sativa L.）品种：D83A/R527（低吸收累积Cd）和辐优838（高吸收累积Cd）在不同质量浓度Cd胁迫下籽粒Cd质量分数及不同生育时期水稻根、茎、叶内Cd的吸收积累量及其动态变化特点。结果表明,两种水稻品种在Cd胁迫下籽粒Cd积累量差异显著,辐优838在1.0 mg·L^-1 Cd质量浓度胁迫下籽粒Cd质量分数就已超过国家食品卫生标准;在1.0~3.0 mg·L^-1 Cd质量浓度胁迫下,D83A/R527籽粒内Cd质量分数仅为辐优838的50~60%。随着Cd处理浓度增加和生育时期推进,两种水稻各部位Cd吸收量均表现为逐渐增加,其增加幅度总体表现为：辐优838〉D83A/R527;不同部位中,根的积累效应最强,叶片吸收积累能力最低,辐优838茎、叶吸收积累效率分别是D83A/R527的1.5~2.0倍左右。在1.0~3.0mg·L^-1 Cd胁迫下,水稻Cd积累差异较为显著的时期为灌浆期,辐优838的根系向茎、叶的转移效率大于D83A/R527,且D83A/R527主要表现为由根系向茎Cd转移效率较高,叶片Cd积累相对较少。灌浆期是水稻籽粒干物质积累的重要时期,也是吸收累积Cd的重要时期,这为筛选低吸收积累水稻品种和调控Cd在水稻籽粒中的吸收累积奠定了重要理论基础。     

水稻土中7个水稻品种对土壤Cd、Pb的富集与转运:田间研究

近年来,稻米Cd、Pb含量超标问题频繁出现,稻米质量安全备受关注。通过在Cd-Pb复合污染土壤上,采用田间试验方法研究了7个水稻(Oryza.sativa L.)品种(宜优673、东联5号、花优63、春优84、浙优18、甬优9号和台粳8号)对土壤Cd和Pb的富集与转运能力,并探讨了影响稻米富集Cd和Pb的因素,以期为Cd、Pb污染农业土壤的安全利用提供依据。研究结果表明,Cd、Pb主要富集在水稻根中,Cd、Pb在各组织中的含量分别表现为根茎叶糙米、根叶茎糙米。糙米Cd、Pb含量分别为0.06~0.18、0.09~0.31 mg·kg~(-1),品种间Cd、Pb含量差异均达显著水平(P0.05);供试水稻糙米中Cd含量均未超标(0.2 mg·kg~(-1),GB2762—2017),除台粳8号以外,其他品种糙米Pb含量也未超标(0.2 mg·kg~(-1),GB2762—2017)。糙米Cd含量随稻谷产量的升高而升高,糙米Pb含量则随稻谷产量的升高而降低。不同水稻品种对土壤Cd的富集能力表现为:春优84甬优9号浙优18宜优673东联5号、花优63、台粳8号,最大相差2.4倍;对土壤Pb的富集能力表现为:台粳8号宜优673浙优18花优63、春优84、甬优9号东联5号,最大相差3.3倍。高根表铁膜Cd含量促进了水稻根系对Cd的吸收,但高根表铁膜Pb含量则抑制了根系对Pb的吸收。糙米Cd含量随Cd在茎-糙米和叶-糙米之间的转移系数的升高而升高(P0.01),但糙米Pb含量与Pb在茎-糙米和叶-糙米之间的转移系数无明显相关(P0.01)。台梗8号是低产低Cd累积品种,东联5号为高产低Cd积累品种,东联5号和甬优9号为高产低Pb积累品种,在Cd污染、Pb污染或Cd-Pb复合污染的农田上可以酌情选种。     

外加镉对水稻镉吸收、亚细胞分布及非蛋白巯基含量的影响

研究不同水稻(Oryza sativa)品种外加Cd处理下镉吸收特征、PCs(主要是非蛋白巯基)的解毒机制及从微观水平探寻亚细胞镉的分布状况,对了解不同水稻基因型的耐Cd机理有重要意义。通过盆栽实验研究了不同外加Cd处理对水稻体内Cd的吸收累积、亚细胞分布及非蛋白巯基含量的影响。结果表明,外加Cd胁迫显著诱导根合成NPT-SH,外加Cd及品种差异对水稻体内Cd的吸收具有不同程度的影响,两品种相比,不加Cd处理下,品种J196地上部Cd含量/根系Cd含量的比值高于中浙优1号;当外加Cd浓度达到5 mg·kg-1时,品种A根系向地上部转移的Cd远高于品种C,分为25.7%和7.4%;但在外加Cd处理达到25 mg·kg-1时,两品种间无显著差异。根中NPT-SH的诱导量与水稻根系内Cd的含量变化一致。外加Cd处理下,品种J196根系内NPT-SH含量均高于中浙优1号,从细胞水平上表明中浙优1号可能具有从根系向茎叶的高镉转运能力。同时以差速离心法探究Cd在两杂交水稻品种不同器官的亚细胞分布为根系细胞的Cd大部分存在于细胞壁中,占52.6%~83.2%,少部分存在于细胞可溶部分(细胞质),其镉含量分布的百分率为3.0%~10.1%,且根系细胞壁中J196的分布率高于中浙优1号;表明J196的根系细胞壁的具有较强的固Cd能力;和对照相比,外加Cd促使中浙优1号根系细胞内可溶物向地上部移动,且高Cd处理下,Cd在中浙优1号细胞内溶物的分配率大于J196,从而在亚细胞水平上推测了品种中浙优1号为高转运品种的可能机制。     

镉胁迫对两品种水稻生长及抗氧化酶系统的影响

水稻Oryza sativa L.被认为是Cd吸收最强的大宗谷类作物,本研究采用网室盆栽实验研究2个籽粒镉积累水平不同的水稻品种（中浙优1号、高Cd品种和J196、低Cd品种）,研究不同浓度Cd处理对水稻幼苗生长和抗氧化酶系统的影响。结果表明：高Cd水稻品种的Cd耐性高于低Cd水稻品种,表现为前者体内的MDA含量低于后者,而SOD、CAT、POD活性高于低Cd品种;在Cd胁迫下,高Cd品种的SOD 活性、CAT活性随Cd处理浓度增加先增后降,在10 mg·kg-1时达到峰值,POD活性则为先降后增,在Cd浓度为5 mg·kg-1时达到峰值;而低Cd品种随着外源Cd浓度增长,3种酶活性在25 mg·kg-1达到峰值,除SOD比对照降低外,CAT和POD分较对照升高38.07%和62.10%,表明在本试验处理下,Cd胁迫下,两品种中3种抗氧化酶保护作用不同,高Cd品种CAT的保护性最强,低Cd品种POD的保护作用最强。但本研究对两品种生长性状的研究却发现,高Cd品种的根系耐受指数及根系鲜质量显著低于低Cd品种,这可能和水稻对Cd的耐受原因多元化,且本实验条件下的Cd处理未产生植株生长抑制,Cd敏感品种自身的保护机制有关。     

不同生育期类型水稻对镉积累的研究

以江苏省有代表性的早熟中粳、中熟中粳、迟熟中粳、早熟晚粳和中熟晚粳5种生育期类型的56个粳稻品种为材料,在Cd污染农田中研究不同生育期类型粳稻品种Cd积累特性.结果表明,56个供试水稻品种籽粒Cd含量变化范围为0.014～0.054 mg·kg-1,水稻籽粒Cd含量在品种间差异显著(P＜0.05),其中籽粒Cd含量最高的品种是ELTO,扬粳687、泗阳1382、广陵香粳和武香粳9号水稻籽粒Cd含量较低.不同生育期类型水稻籽粒Cd含量以早熟中粳较高,中熟中粳较低,分别为0.024和0.020 mg·kg-1.不同生育期类型水稻籽粒Cd富集系数差异不显著,而不同生育期类型间转运系数存在差异.     

外加Cd对两水稻品种细胞超微结构的影响研究

为了研究Cd在不同水稻品种(Oryza sativa L.)细胞中的分布位点及其耐Cd的具体表征状况,以子粒Cd积累水平不同的两水稻品种(品种A:中浙优1号,子粒高Cd含量品种;品种C:J196,子粒低Cd含量品种)为材料,进行盆栽实验,设不加Cd处理(CK)和加Cd处理(25mg·kg-1),采用透射电镜技术研究了外加Cd对两水稻品种细胞超微结构的影响.结果表明:Cd处理下两水稻品种的部分根细胞有Cd沉积现象,但不同品种的沉积部位表现不同,品种A主要在液泡边缘而品种C则在细胞壁和细胞间隙,表明不同水稻品种根系的耐Cd机制不同,品种A主要表现为液泡区室化,而品种C主要表现为细胞壁上有特定沉积.水稻叶肉细胞器中的叶绿体和线粒体是对Cd胁迫较为敏感的细胞器,外加Cd对茎叶细胞超微结构造成的伤害主要表现在使叶绿体上淀粉粒消失,叶绿体空泡化,部分线粒体出现肿胀或解体现象,品种C的受害程度高于品种A。     

膨润土对镉胁迫下水稻幼苗生理生化特性的影响

为了探讨膨润土钝化修复镉(Cd)污染土壤对水稻幼苗生理生化特性的响应,通过盆栽试验研究了膨润土对Cd胁迫下水稻幼苗地上部生物量,叶片叶绿素含量,SOD、POD活性以及MDA含量的影响.结果表明,膨润土在不同程度上提高了水稻幼苗叶片叶绿素含量,促进了水稻幼苗的生长和发育,地上部生物量随膨润土投加量的增加而增大.单一Cd污染土壤中,水稻幼苗叶片SOD活性变化不明显,而幼苗根系SOD活性随Cd浓度的增加而显著降低(P＜0.05),投加膨润土后整体上提高了根系SOD活性.单一Cd污染土壤中,水稻幼苗叶片和根系POD活性随Cd浓度的增加而均呈现先应激性升高然后降低的变化趋势,投加膨润土后叶片POD活性有所降低,而5 ～50 g·kg-1膨润土处理显著提高根系POD活性(P＜0.05),比未投加膨润土处理分别增加13.2％ ～22.4％、4.9％ ～9.5％、44.8％～80.6％和6.9％～49.6％.单一Cd污染土壤中,水稻幼苗叶片和根系MDA含量随着Cd浓度的升高而升高,与无Cd胁迫对照相比,分别增加139.0％和158.1％;投加膨润土处理水稻幼苗MDA含量显著降低,膜脂过氧化作用明显减弱.因此,膨润土能有效缓解Cd胁迫对水稻幼苗的毒害作用,可用于Cd污染土壤的钝化修复.     

2种常规水稻Cd、Zn吸收与器官分配的生育期变化：品种、土壤和Cd处理的影响

Cd在土壤-作物-膳食食物链中的迁移是人类对环境Cd暴露及其健康风险的主要途径,而水稻是子粒Cd积累最强的大宗作物之一.采用全生育期淹水盆栽试验研究了2种常规水稻(高Cd吸收品种“苏香粳1号”和低Cd吸收品种“99-22”)在添加Cd(2mg·kg-1)和不添加Cd处理下对2种土壤(红沙泥田,乌栅土)中Cd、Zn的吸收及其生育期变化.结果表明:1)常规水稻对Cd、Zn的吸收积累受土壤、品种和外源Cd的影响.Cd处理、土壤、品种间的正交互作用(高Cd吸收品种植于高Cd处理且Cd有效性高的红壤中)使常规稻植株Cd/Zn比成数十倍提高,从而使子粒Cd/Zn比产生强烈升高;2)水稻对Cd、Zn的吸收强度因不同生育期而异,Cd吸收的主要时期是分蘖期和成熟期,而Zn吸收的主要时期则是分蘖期、抽穗期和灌浆期.在整个生育期中,水稻Cd吸收伴随着对Zn的排斥现象,这在高Cd吸收下尤为强烈;3)水稻各器官对Cd、Zn的吸收分配无论是同品种的生育期间抑或同生育期时的不同品种间均有显著差异.Cd积累量为根系>穗粒>茎叶,而Zn却表现为茎叶>根系、穗粒.观察到水稻吸收的Cd在生育后期向穗粒的强烈运移.相对于低Cd吸收品种来说,Cd向穗粒转运较强,而Zn的转运较弱是高Cd吸收品种子粒Cd积累强而Cd/Zn比高的植株因素.     

Hg2+胁迫下两优培九和武运粳7号水稻幼苗抗性差异的研究

以三叶期的水稻幼苗为材料 ,比较了Hg2 污染对杂交稻两优培九和常规稻武运粳 7号的叶绿素含量、类囊体膜光系统Ⅰ (PSⅠ )和光系统Ⅱ (PSⅡ )电子传递活性、细胞膜透性、过氧化物酶 (POD)、过氧化氢酶 (CAT)活性和脯氨酸含量的影响。结果表明 ,随着Hg2 处理浓度的增加 ,两优培九和武运粳 7号的叶绿素含量、PSⅠ和PSⅡ的电子传递活性降低 ,而 2者的细胞膜透性、脯氨酸含量升高 ,两优培九的CAT活性、武运粳 7号的POD和CAT活性呈现先升后降的趋势 ,但两优培九的POD活性则呈现升高的趋势。两优培九对Hg2 污染的抗性明显大于武运粳 7号。     

Hg^2＋胁迫下两优培九和武运粳7号水稻幼苗抗性差异的研究

以三叶期的水稻幼苗为材料，比较了Hg^2 污染对杂交稻两优培九和常规稻武运粳7号的叶绿素含量、类囊体膜光系统Ⅰ（PSⅠ）和光系统Ⅱ（PSⅡ）电子传递活民生、细胞膜透性，过氧化物酶（POD）、过氧化氢酶（CAT）活性和脯氨酸含量的影响。结果表明，Hg^2 处理浓度的增加，两优培九和武运粳7号的叶绿素含量、PSⅠ和PSⅡ的电子传递活性降低，而2者的细胞膜透性、脯氨酸含量升高，两优培九的CAT活性、武运粳7号和POD和CAT活性呈现先升后降的趋势，但两优培九的POD活性则呈现升的趋势。两优培九对Hg^2 污染的抗性明显大于武运粳7号。     

Rice seedlings under cadmium stress: effect of silicon on growth,cadmium uptake,oxidative stress,antioxidant capacity and root and leaf structures

In this study, the effect of silicon (Si) addition on cadmium (Cd) toxicity in rice seedlings was investigated. After a series of screening experiments, 50 μmol·L^?1 of Cd and 10 μ mol·L^?1 of Si were selected. Treatment of rice seedlings with Cd (50 μ mol·L^?1) resulted in significant accumulation of this metal in roots and shoots. The data revealed that accumulation of Cd resulted in oxidative stress in rice seedlings as evidenced by increased accumulation of hydrogen peroxide (H₂O₂) and malondialdehyde (MDA; a peroxidation product of lipids). However, addition of Si (10 μ mol·L^?1) together with Cd prevented accumulation of Cd, H₂O₂ and MDA. Antioxidant capacity was decreased by Cd but enhanced by Si addition. Cd decreased the length and frequency of root hairs, stomatal frequency, and distorted leaf mesophyll cells and vascular bundles. However, addition of Si together with Cd reduced these abnormalities. The results showed that addition of exogenous Si protected rice seedlings against Cd toxicity by preventing Cd accumulation and oxidative stress (H₂O₂ and MDA accumulation) by increasing Si accumulation and antioxidant capacity, which maintained the structure and integrity of leaf and root.     

茄子苗对镉积累和耐性的品种间差异

通过盆栽实验方法研究了13种茄子幼苗对镉(Cd)积累与耐性的品种间差异。结果表明,这些茄子幼苗根及地上部Cd含量均随土壤中外加Cd的量的增加而提高。品种间存在着显著差异(P<0.05),其中Cd含量最高品种根部和地上部的Cd含量分别为Cd含量最低品种的2.1、2.4倍(2mg·kg-1Cd处理组)和1.5、1.6倍(4mg·kg-1Cd处理组)。不同品种幼苗对Cd的富集系数均大于1,表现出较强的富集能力。但转运系数均小于1,Cd从根部向地上部转移能力较弱,大多数品种间差异不大。当Cd添加量为2mg·kg-1时,只有绿龙长茄地上部生物量显著下降(P<0.05)。当Cd添加量提高到4mg·kg-1时,6个品种地上部生物量显著下降(P<0.05),这些品种对Cd的耐性较弱。综合评价,辽茄三号对Cd积累的含量最低,富集系数和转移系数也较低,对Cd具有较强的耐性,具有Cd低积累特征。     

镉和温度预暴露对小麦吸收镉的影响

土壤中重金属Cd污染是一个累积过程,污染历史会影响植物对土壤中Cd的吸收.近年来,随着全球气候的变暖,温度对Cd的生物有效性的影响日益引起关注.通过模拟土壤溶液,研究了Cd的浓度、温度和预暴露时间对小麦吸收Cd的影响.小麦在浓度为0.01和0.1μmol·L-1的Cd中经过不同时间的预暴露后进行6h的短期吸收实验.结果发现,经1d预暴露后,小麦根部吸收Cd的量有增加趋势,这说明Cd对小麦产生了刺激作用,小麦地上部分的含Cd量也有所增加但不显著.经5d预暴露后,小麦对Cd产生了抗性,这使得小麦根部降低了对Cd的吸收量;并且当Cd为0.1μmol·L-1时,根部Cd吸收量的降低最为明显;由于Cd从根部向地上部迁移是一个复杂的生理过程,预暴露对地上部分Cd含量的影响没有根具有规律性;经过37℃高温胁迫4h后,小麦根部及地上部分的Cd含量减少高达40%;预暴露和高温共同作用后,其减少量更多,这说明预暴露和高温共同作用能够减少小麦对Cd的吸收量.     

重金属胁迫对日本对虾(Penaeus japonicas )胚胎发育的影响

以受精1 h以内的日本对虾受精卵为实验对象,采用静水试验方法,研究了Zn、Hg、Cu、Pb、As、Cd和Cr 7种重金属对日本对虾胚胎发育的影响。结果表明,在实验浓度范围内,7种重金属中Hg、Cu对日本对虾胚胎发育毒性最大,其次是Zn、As、Cd,Pb和Cr无明显影响。Hg、Cu、Cd、As、Zn对日本对虾胚胎LC₅₀值分别为：0.0177 mg·L^-1、0.1070 mg·L^-1、1.6057 mg·L^-1、3.3682 mg·L^-1、8.2644 mg·L^-1,致死效应最低可观测效用浓度（LOEC）分别为0.0037 mg·L^-1、0.0166 mg·L^-1、0.1302 mg·L^-1、1.1572 mg·L^-1、2.1522 mg·L^-1;抑制发育LOEC分别为0.0062 mg·L^-1、0.0176 mg·L^-1、0.4002 mg·L^-1、1.9497 mg·L^-1、0.0617 mg·L^-1。随着Hg、Cu浓度的升高,胚胎孵化率不断下降,无节幼体死亡率不断上升,在Hg 0.0256 mg·L^-1浓度组中,胚胎48 h死亡率达到100%。以上结果说明,Hg、Cu等重金属的存在会延缓日本对虾胚胎的发育速度,随着重金属浓度的增加,滞育现象愈加明显,在Cu 0.32 mg·L^-1浓度组中,未见无节幼体孵出。     

Effects of salinity on the uptake of lead and cadmium by two mangrove species Rhizophora apiculata Bl. and Avicennia alba Bl.

The uptake of lead (Pb) and cadmium (Cd) by Rhizophora apiculata and Avicennia alba under various salinity levels was examined using hydroponic cultivations. After 3 months of exposure at four levels of Pb (0, 0.03, 0.3 and 3 mg·L^?1) and four levels of Cd (0, 0.005; 0.05 and 0.5 mg·L^?1) at different salinities (0, 15 and 30), uptake of the metals was shown to be differently affected by salinity. For uptake of Pb by R. apiculata, the salinity effect was not significant for the leaves and was most significant in the stem, whereas for A. alba, the effect of salinity was significant only in the stem. Uptake of Pb in the roots and stems of both species was similar, but a higher concentration was recorded in the leaves of A. alba. Salinity was shown to affect the uptake of Cd by all tissues of R. apiculata, but most significantly roots. For A. alba, salinity significantly affects the total uptake of Cd, but this is most significant in the roots. The two mangrove species demonstrated different mechanisms of metal distribution into their organs which may be related to different adaptation mechanisms to saline conditions.     

三氯生对青海弧菌Q67和人乳腺癌细胞MCF-7的时间毒性

三氯生(triclosan,TCS)是一种广谱性抗菌剂,2005年欧盟水框架指令将TCS列为一种新型污染物。目前对TCS的研究局限于急性毒性实验,关于TCS毒性随时间的变化以及不同溶解状态下TCS的毒性差异的研究却鲜有报道。应用以96孔微板为暴露反应载体的微板毒性分析法,添加氢氧化钠(NaOH)或使用二甲亚砜(DMSO)作为助溶剂溶解TCS,分别测定其对青海弧菌Q67的相对发光抑制毒性(15min急性毒性和时间毒性)和对人乳腺癌细胞MCF-7在不同暴露时间(24、48和72h)内的细胞增殖抑制毒性。Q67的急性毒性实验结果表明,碱性条件下TCS的毒性(EC50=3.97(10-8mol.L-1)大于DMSO作为助溶剂时的毒性(EC50=1.68(10-4mol.L-1)。无论碱性条件还是DMSO助溶,TCS在不同暴露时间内对Q67的时间毒性没有明显差异。在不同暴露时间下MCF-7增殖抑制率实验中,DMSO作为助溶剂时,TCS的最高实验浓度为1.46(10-3mol.L-1,随着暴露时间的延长,抑制率在24、48和72h时分别为27.8%、44.2%和62.4%;碱性环境时TCS的最高实验浓度为1.39(10-6mol.L-1,随着暴露时间的延长,抑制率在24、48和72h时分别为20.2%、55.8%和73.9%。研究表明,在DMSO和NaOH作为助溶剂的条件下,TCS对MCF-7均存在时间毒性差异,并且NaOH碱性溶液中TCS对MCF-7的毒性远大于DMSO作为助溶剂时的毒性。     

Metabolic responses of Azolla pinnata to cadmium stress: photosynthesis,antioxidative system and phytoremediation

This present study deals with the growth, photosynthesis, oxidative stress and phytoremediation character of Azolla pinnata L. exposed to different levels (0.05, 0.1, 0.5, 1.0, 1.5 and 2.0 mg·L^?1) of cadmium (Cd). Significant accumulation of Cd in Azolla fronds was noticed after 24 and 96 h of exposure and the accumulation rate was dose and time dependent. Growth of A. pinnata increased significantly after both exposure times with and without metal. At lower Cd doses (0.05 and 0.1 mg·L^?1), growth and photosynthesis of A. pinnata showed a marginal increase over the respective control, however, at higher Cd doses (0.5, 1.0, 1.5 and 2.0 mg·L^?1), a decreasing trend was noticed. At lower doses, Azolla fronds could counterbalance the negative effect of enhanced levels of superoxide radicals (SOR) and hydrogen peroxide (H₂O₂) through the greater activity of antioxidative enzymes. The decaresing trends in catalase and peroxidase activity at higher Cd doses suggest that Azolla fronds were not able to mitigate the negative effects of H₂O₂, hence an increase in malondialdehyde content was noticed. The study concludes that up to 0.1 ,mg·L^?1 Cd, A. pinnata can flourish and be used as biofertiliser and for phytoremedial purposes in Cd-contaminated fields; beyond this concentration poor growth may restrict its application.     

2个镉耐性差异箭舌豌豆品种中镉的化学形态及亚细胞分布

通过溶液培养实验,研究了镉胁迫下2个箭舌豌豆(Vicia sativa)品种(镉耐性品种L3,镉敏感品种ZM)中镉的积累、镉的亚细胞分布和化学形态以及非蛋白巯基化合物(NPTs)的响应。结果表明2个箭舌豌豆品种根较地上部积累更多的镉。镉在箭舌豌豆根、茎和叶中主要分布于可溶性组分,敏感品种ZM根中可溶性组分的镉含量和占总镉的比例显著高于耐性品种L3。细胞壁结合镉占总镉的比例在2个品种中均为叶>茎>根。镉在箭舌豌豆根和茎内主要以去离子水(d-H2O)提取态和1 mol·L-1氯化钠(Na Cl)提取态存在,ZM根中d-H2O提取态镉的含量和比例显著大于L3。箭舌豌豆叶中镉主要以2%醋酸(HAc)提取态存在。ZM叶中80%乙醇提取态镉的比例大于L3,0.6 mol·L-1盐酸(HCl)提取态镉和残渣态镉的比例小于L3。2个品种根和茎中NPTs的含量在镉胁迫下显著升高,ZM根中NPTs的含量显著大于L3。研究结果表明,箭舌豌豆镉解毒的主要机制包括限制镉由根部向地上部转运和液泡隔离。此外,根和茎中镉与有机酸结合和NPTs螯合,叶中镉以移动性低、毒性低的形态存在也是箭舌豌豆镉解毒的重要机制。ZM较L3根中更多镉以移动性高的形态存在,L3较ZM叶中更多镉以难移动的形态存在,是L3较ZM具有更高镉耐性的重要原因。     

Effects of Cadmium on Nutrient Uptake and Translocation by Indian Mustard

Plants that hyperaccumulate metals are ideal subjects for studying the mechanisms of metal and mineral nutrient uptake in the plant kingdom. Indian Mustard (Brassica juncea) has been shown to accumulate moderate levels of Cd, Pb, Cr, Ni, Zn, and Cu. In this experiment, 10 levels of Cd concentration treatments were imposed by adding 10–190 mg Cd kg^–1 to the soils as cadmium nitrate [Cd(NO₃)₂]. The effect of Cd on phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), and the micronutrients iron (Fe), manganese (Mn), copper (Cu), and zinc (Zn) in B. juncea was studied. Plant growth was affected negatively by Cd, root biomass decreased significantly at 170 mg Cd kg^–1 dry weight soils treatment. Cadmium accumulation both in shoots and roots increased with increasing soil Cd treatments. The highest concentration of Cd was up to 300 mg kg^–1 d.w. in the roots and 160 mg kg^–1 d.w. in the shoots. The nutrients mainly affected by Cd were P, K, Ca, Fe, and Zn in the roots, and P, K, Ca, and Cu in the shoots. K and P concentrations in roots increased significantly when Cd was added at 170 mg kg^–1, and this was almost the same level at which root growth was inhibited. Zn concentrations in roots decreased significantly when added Cd concentration was increased from 50 to 110 mg kg^–1, then remained constant with Cd treatments from 110 to 190 mg kg^–1. However, Zn concentrations in the shoots seemed less affected by Cd. It is possible that Zn uptake was affected by the Cd but not the translocation of Zn within the plant. Ca and Mg accumulation in roots and shoots showed similar trends. This result indicates that Ca and Mg uptake is a non-specific process.     

Interaction between cadmium,lead and potassium fertilizer (K<Subscript>2</Subscript>SO<Subscript>4</Subscript>) in a soil-plant system

A pot experiment was conducted to examine the influence of potassium (K) fertilizer (K₂SO₄) application on the phytoavailability and speciation distribution of cadmium (Cd) and lead (Pb) in soil. Spring wheat (Triticum aestivum L.) was selected as the test plant. There were seven treatments including single and combined contamination of Cd and Pb. CdCl₂·2.5 H₂O and Pb(NO₃)₂ were added to the soil at the following dosages: Cd + Pb = 0.00 + 0.00, 5.00 + 0.00, 25.0 + 0.00, 0.00 + 500, 0.00 + 1000, 5.00 + 500 and 25.0 + 1000 mg kg⁻¹, denoted by CK, T1, T2, T3, T4, T5 and T6, respectively. The K fertilizer had five levels: 0.00, 50.0, 100, 200 and 400 mg K₂O kg⁻¹ soil, denoted by K0, K1, K2, K3 and K4, respectively. The results showed that the K fertilizer promoted the dry weight (DW) of wheat in all treatments and alleviated the contamination by Cd and Pb. The application of K₂SO₄ reduced the uptake of Cd in different parts including roots, haulms and grains of wheat; the optimum dosage was the K2 level. K supply resulted in a significant (P < 0.05) decrease in the soluble plus exchangeable (SE) fraction of Cd and there was a negative correlation (not significant, P > 0.05) between the levels of K and the SE fraction of Cd in soil. The application of the K fertilizer could obviously restrain the uptake of Pb by wheat and there were significant (P < 0.05) negative correlations between the concentrations of Pb in grains and the levels of K in soil. K supply resulted in a decrease in the SE fraction of Pb (except the K1 level) from the K0 to K4 levels. At the same time, the application of the K fertilizer induced a significant (P < 0.05) decrease in the weakly specifically adsorbed (WSA) fraction of Pb and a significant (P < 0.05) increase in the bound to Fe–Mn oxides (OX) fraction of Pb. At different K levels, the concentration of Pb in the roots, haulms and grains had a positive correlation with the SE (not significant, P > 0.05) and WSA (significant, P < 0.05) fractions of Pb in the soil. All the K application levels in this experiment reduced the phytoavailability of Cd and Pb. Thus, it is feasible to apply K fertilizer (K₂SO₄) to alleviate contamination by Cd and/or Pb in soil. Moreover, the level of K application should be considered to obtain an optimal effect with the minimum dosage.