Interactions of cadmium and aluminum toxicity in their effect on growth and physiological parameters in soybean

The effect of Al and Cd on the growth, photosynthesis, and accumulation of Al, Cd and plant nutrients in two soybean genotypes were determined using hydroponic culture. There were six treatments: pH 6.5; pH 4.0; pH 6.5+1.0 μmol/L Cd; pH 4.0+1.0 μmol/L Cd; pH 4.0+150 μmol/L Al; pH 4.0+1.0 μmol/L Cd+150 μmol/L Al. The low pH (4.0) and Al treatments caused marked reduction in root length, shoot height, dry weight, chlorophyll content (SPAD value) and photosynthetic rate. Al-sensitive cv. Zhechun 2 accumulated comparatively more Al and Cd in plants than Al-tolerant cv. Liao 1. Compared with pH 6.5, pH 4.0 resulted in significant increase in Cd and Al concentration in plants. Combined application of Cd and Al enhanced their accu-mulation in roots, but caused a reduction in shoots. The concentrations of all 10 nutrients (P, K, Ca, Mg, Fe, Mn, Cu, Zn and B), except Mo were also increased when plants were exposed to pH lower than pH 6.5. Al addition caused a reduction in the con-centration of most nutrients in plant roots and shoots; but K, Mn and Zn in roots were increased. Treatments with Cd alone or together with Al reduced the concentrations of all the plant nutrients in plants. Al-sensitive genotype Zhechun 2 has lower nutrient concentration than Al-tolerant genotype Liao 1. The current findings imply that Al and Cd are synergistic in their effect on plant growth, physiological traits and nutrient uptake.

Ecotoxicity of Cadmium to Maize and Soybean Seedling in Black Soil

Ecotoxicity and bioavailability of cadmium(Cd)to the maize(Zea mays L.)and the soybean(Glycine max(L.)Merr.)were investigated by acute toxicity experiment in the laboratory with black soil.Ecotoxicity and bioavailability of Cd were quantified by calculating the median effective concentration(EC50)and bioaccumulation factor(BAF).The measurement endpoints used were seed germination and seedling growth(shoot and root).The results showed that concentrations of Cd in the soil had adverse effect on the growth of roots and shoots.Seed germination was not the sensitive indicator for the ecotoxicity of Cd in the soil,while the growth of roots was the most sensitive measurement endpoint.Absorbability and transport of Cd in plants depended on the test crop species and Cd concentrations in the soil.The maize retains more Cd in its roots,while the soybean transports more Cd to the shoots from roots.

Groundwater Level Effect on Redox Potential, on Cadmium Uptake and Yield of Soybean

In this greenhouse experiment, we investigated the effects of two constant groundwater levels: 10 cm groundwater level (GW-10) and 40 cm groundwater level (GW-40) and one change groundwater level, which was 40-10-40 cm (GW-40-10-40) on Cadmium (Cd) uptake and seed yield of Soybean plant in Cd contaminated soils (1.57 mg·kg-1). The experimental soil layer was made with gravel layer (14 cm), non-polluted soil (15 cm) and polluted soil (25 cm). The redox potential of every soil layer was measured from sowing to harvesting. The soil layer (10 – 40 cm) of GW-10 was always in reduction condition and that of GW-40 was always in oxidation condition. First 50 days of GW 40-10-40 were in oxidation and next 50 days in reduction and final 20 days again returned in oxidation condition. Soybean seed Cd concentration was significantly highest in GW-40-10-40 (1.16 ± 0.13 mg·kg-1) and lowest in GW-40 (0.81 ± 0.12 mg·kg-1). Cd concentration of stem was found significantly higher in GW-40 (1.7 ± 0.2 mg·kg-1) than GW-10 (0.91 ± 0.08 mg·kg-1) and GW-40-10-40 (1.28 ± 0.13 mg·kg-1). There was no significant difference in root Cd concentration among these 3 treatments. Main stem height of soybean plant and 100 seed weight of GW-40 were significantly higher than those of GW-10. The result revealed that, soil redox condition is an important factor for Cd uptake in soybean plant and seed yield of soybean. This study will help to manage the farming process more appropriately with the aim of minimizing uptake of Cd and other toxic metals in grain crops.

大豆GmbHLH041基因的生物信息学分析及对镉胁迫的响应

为探讨大豆Gmb HLH041转录因子在应答镉胁迫中的作用,根据前期的镉胁迫前后大豆根系转录组测序结果,筛选获得响应Cd胁迫的Gmb HLH041基因,利用NCBI和Phytozome数据库,结合生物信息学软件对Gmb HLH041基因进行预测分析,并通过q RT-PCR的方法检测大豆根系中Gmb HLH041基因在50μmol/L Cd SO4胁迫0,24 h的表达情况。结果显示,Gmb HLH041基因编码542个氨基酸,相对分子质量为61.17 ku,理论等电点为5.89。二级结构预测结果显示,该氨基酸序列主要以无规则卷曲(39.48%)、α-螺旋(37.27%)和伸展链(16.61%)的形式存在,从拟南芥b HLH家族中的12个亚家族中挑选了24个b HLH蛋白并结合其他物种中亲缘关系较近的b HLH蛋白,对Gmb HLH041进行系统进化树分析发现,Gmb HLH041与野生大豆和狭叶羽扇豆的b HLH041蛋白亲缘关系较近,Gmb HLH041划分到拟南芥b HLH家族第4亚族Ⅳd中。根据进化树的分析结果,选取与Gmb HLH041亲缘关系最近的Gsb HLH041、Lab HLH041以及拟南芥第4亚族Ⅳd中的AT5G56960进行多重比对,结果显示,Gmb HLH041含有一个保守的b HLH结构域;荧光定量PCR结果显示,Gmb HLH041基因在50μmol/L Cd SO4胁迫24 h后表达量极显著上升,说明Gmb HLH041基因在Cd胁迫应答中可能发挥着重要的作用。

大豆bHLH转录因子家族成员的进化及功能分化研究

碱性螺旋-环-螺旋蛋白(basic Helix-Loop-Hleix,bHLH)转录因子家族是动植物中最大的转录因子家族之一,主要由碱性氨基酸区域和螺旋-环-螺旋区域组成,在动植物生长发育和胁迫应答反应中发挥着重要作用.本研究通过对大豆全基因组生物信息学分析和分子生物学研究手段,深入研究了大豆bHLH基因家族的进化机制,同时探讨了该基因家族在大豆中的功能分化.结果表明,大豆中含有340个非冗余的bHLH基因家族成员,通过对这些成员的Pfam蛋白结构域、Motif组成和系统进化关系的分析,将这些成员分为15组共24个亚家族,在大豆20条染色体上呈现不均匀分布.bHLH理化性质差异较大,编码的大豆氨基酸数量为91～815aa,相对分子量为10 273.88～91 300.38,理论等电点为4.56～10.40;碱性氨基酸区含有His5-Glu9-Arg13保守序列,与靶基因结合有关,HLH区含有Arg23和Arg55,与形成二聚体有关,同时含有5种保守元件.多数成员在大豆根以及花发育的5个时期中具有组织表达特异性,不同基因表达量差异较大.

构树BpbHLH149转录因子转录酵母的Cd胁迫响应功能

构树(Broussonetia papyifera(Linn.)L’Hert.ex Vent)是我国重要的扶贫攻坚树种,在矿区植被恢复中占有重要地位。为探究构树的抗镉响应适应分子机制,筛选优良抗逆基因,研究结果从构树中克隆获得一条bHLH转录因子(命名为BpbHLH149)基因,对其基本生物信息、Cd胁迫响应及转化酵母的功能进行分析,预测BpbHLH149响应镉的功能。结果显示:基因开放读码框(ORF)长630 bp,推导蛋白的分子质量为22968.42 u,含有209个氨基酸,理论等电点为11.35。在150μmol·L^(-1)CdCl_(2)处理下,BpbHLH149基因被显著诱导,在12 h时BpbHLH149在根中的表达相对于对照上调了18.2倍。转入BpbHLH149的酵母在Cd胁迫下表现出比对照更高的生存活性。当CdCl_(2)质量分数高于0.6%时,转基因酵母的生长活力是对照的1.54~1.71倍。表明BpabHLH149基因具有响应镉胁迫的能力,且能提高酵母的抗性,BpabHLH149基因可作为构树逆境应答的重要候选基因。

大豆耐涝bHLH转录因子筛选及生物信息学分析

为研究大豆bHLH转录因子与涝害响应相关性,为大豆耐涝性研究提供理论基础,本研究对强耐涝性品种齐黄34进行没顶淹水处理,分析转录组测序结果,筛选差异表达的bHLH转录因子并对其进行生物信息学分析,采用荧光定量PCR方法验证主要差异表达bHLH转录因子编码基因的表达情况,并通过生物信息学方法分析基因结构和互作蛋白。结果显示:涝害胁迫下共发现7个差异表达的bHLH转录因子,它们的同源性并不高,属于不同类型的bHLH。主要差异表达bHLH基因GmbHLH25-15(Glyma.15G06680)的表达量变化情况与转录组数据趋势一致,呈现下调表达。预测到10个蛋白可与该蛋白互作,互作蛋白都是铵转运蛋白,其中4个蛋白编码基因的表达量在转录组测序结果中呈现显著性差异。推测在无氧条件下,GmbHLH25-15可能通过调控铵转运蛋白进而调节铵态氮的吸收来供给自身营养,进而抵御涝害胁迫。

Synergistic interaction of NaCl and Cd on growth and photosynthetic parameters in soybean genotypes differing in salinity tolerance

The effects of salinity(50 mmol/L NaCl) and Cd(1 μmol/L CdCl2) as sole and combined on growth and photosyn-thetic parameters were studied using two soybean genotypes,Huachun 18 and NGB.The concentrations of Cd2+,Zn2+,Ca2+,Mg2+,K+ and Na+ were also determined in seeds and pods.Huachun 18 suffered a more serious decrease than NGB in net photosynthetic rate(Pn) in the treatments of salinity stress alone and combined stress(NaCl+Cd),showing that it is relatively sensitive to salinity.The decrease in Pn caused by salt stress in Huachun 18 was mainly due to the reduced total chlorophyll content and photosynthetic efficiency(the ratio of variable fluorescence to maximal fluorescence,Fv/Fm),whereas the decease in NGB was mainly related to reduced stomatal conductance(Gs).The combined stress of both Na and Cd did not induce further decrease in photosynthesis and fluorescence in the two genotypes relative to salt or Cd stress alone.Greater change in the pod concentrations of Zn2+,Ca2+,Mg2+,K+ and Na+ was detected under salt stress for Huachun 18 than for NGB.The results suggested that the interactive effect of NaCl-Cd on growth and nutrient uptake differs between the two soybean genotypes.

Surfactant Linear Alkylbenzene Sulfonate Effect on Soil Cd Fractions and Cd Distribution in Soybean Plants in a Pot Experiment

A pot experiment was conducted to study the effect of an anionic surfactant linear alkylbenzene sulfonate(LAS) application on cadmium(Cd)fractions in soils and Cd distribution in different tissues of soybean(Glycine max)plants as well as soil pH.Soil samples were treated with three levels of Cd(0,5,and 10 mg kg^(-1))and five levels of LAS(0,5, 15,50,and 100 mg L^(-1)).Results indicated that compared to the control soils(no Cd and no LAS treatment),soil pH increased and available Cd decreased in the soil treated with external Cd and watered with LAS solutions.Meanwhile, soil exchangeable Cd and Cd bound to carbonates decreased;Cd bound to amorphous iron and manganese oxides and Cd bound to organic matter increased.In addition,LAS application could reduce enrichment of Cd in soybean plants, resulting in decreased Cd in the soybean plants.Thus,suitable LAS application could decrease bioavailability and mobility of soil Cd.

重金属镉胁迫对大豆种子萌发与幼苗生长的影响

研究不同质量分数氯化镉胁迫对土培下大豆种子萌发与幼苗生长的影响。结果表明:大豆种子的发芽势、发芽率、发芽指数、活力指数、大豆幼苗的株高、叶长、叶宽、根长、干重、鲜重、耐性指数以及叶绿素质量分数均随氯化镉质量分数的增加呈下降趋势。氯化镉会抑制大豆幼苗的株高、叶长、叶宽、根长的生长,其中,株高和根长对氯化镉的胁迫更为敏感。100 mg·kg^(-1)氯化镉处理的大豆幼苗的耐性指数与对照组差异极显著,第14、21、28 d大豆幼苗的耐性指数分别为42.6%、35.9%、34.4%。不同质量分数氯化镉处理后,大豆叶片中叶绿素质量分数降低,当氯化镉质量分数为100 mg·kg^(-1)时,降低幅度最大。重金属镉进入土壤后,影响大豆种子的萌发以及幼苗正常的生长发育。

施氮对铜镉污染土壤中大豆植株生长及氮磷钾含量的影响

土壤重金属污染加剧使农业生产受到严重威胁,为提高土地重金属污染治理效率,针对施氮能否缓解土壤重金属污染对植物的毒害作用开展研究。通过开展盆栽实验,分别测定大豆植株的生长指标、营养含量和重金属含量,研究施氮对镉(Cd~(2+)4mg/L)和铜(Cu~(2+)16mg/L)污染土壤中大豆植株生长的影响。结果表明:施氮使铜、镉污染土壤中的大豆株高分别增加了43.38%和47.67%,生物量增加了162.01%和218.69%。在含4mg/LCd~(2+)土壤中,施氮使大豆植株根、茎、叶中的氮含量增加120.20%、138.25%和10.21%;根、叶中的磷含量分别上升了66.93%、10.75%,茎部的磷含量下降13.46%;根、茎、叶中的钾含量分别上升了10.97%、37.36%、47.49%;而根、茎、叶中的Cd含量分别降低了50.53%、78.28%、42.31%。在含16mg/LCu~(2+)土壤中,施氮使大豆根、茎、叶中的氮含量分别增加了64.52%、135.71%、55.48%;磷含量分别下降了79.72%、80.30%、43.71%;钾含量分别增加了39.31%、61.43%、104.69%;同时大豆根部的Cu含量降低了48.91%,而茎、叶中的Cu含量无显著变化。综上,施氮可通过促进植物生长,增强其抗逆性,从而缓解土壤重金属污染的毒害作用。

豆饼联合海泡石对水稻镉积累的影响

采用盆栽试验,研究了海泡石、豆饼及二者配施对稻田土壤理化性质、土壤中镉(Cd)的存在形式以及水稻各部位Cd积累的影响。结果表明,海泡石、豆饼及其配施处理均提高了稻田土壤pH值、可溶性盐含量(EC值)和阳离子交换量(CEC值),豆饼与海泡石配施处理组的土壤pH小于单施海泡石处理组;与对照相比,添加豆饼处理土壤有机质含量(SOM)显著提高;与对照相比,各处理组均降低了土壤中DTPA-Cd含量,均使土壤中可交换态Cd向可还原态Cd、可氧化态Cd以及残渣态Cd转化,均不同程度降低了水稻根、茎叶、籽粒中Cd含量。

Graphitic carbon nitride nanosheets mitigate cadmium toxicity in Glycine max L.by promoting cadmium retention in root and improving photosynthetic performance

Cadmium(Cd)pollution poses a serious threat to plant growth and yield.Nanomaterials have shown great application potential for alleviation of Cd toxicity to plants.In this study,we applied graphitic carbon nitride nanosheets(g-C_(3)N_(4)NSs)for alleviation of Cd-toxicity to soybean(Glycine max L.).The g-C_(3)N_(4)NSs supplementation significantly improved plant growth and reduced oxidative damage in the Cd-toxicated soybean seedlings through hydroponic culture.Particularly,the g-C_(3)N_(4)NSs dynamically regulated the root cell wall(RCW)components by increasing pectin content and modifying its demethylation via enhancing pectin methylesterase(PME)activity,therefore greatly enhanced stronger RCW-Cd retention(up to 82.8%)and reduced Cd migration to the shoot.Additionally,the g-C_(3)N_(4)NSs reversed the Cd-induced chlorosis,increased photosynthetic efficiency because of enhancement in F_v/F_mration,Y(Ⅱ)and sugars content.These results provide new insights into the alleviation of Cd toxicity to plants by g-C_(3)N_(4)NSs,and shed light on the application of low-cost and environmental-friendly carbon-based NMs for alleviating heavy metal toxicity to plants.

重金属镉对大豆种子萌发与幼苗生长的影响

为了探索不同浓度重金属镉对大豆种子萌发与幼苗生长的影响,设置5个处理小组,每个处理小组分3个平行小组进行试验。试验结果发现:对照组的发芽率显著高于处理1组和处理2组(P<0.05),极显著地高于处理3和处理4组(P<0.01),各个小组的发芽势相比,均达差异显著性(P<0.05);随着重金属镉浓度的升高,大豆的发芽指数和活力指数逐渐降低,和对照组相比,处理1组—处理4组的发芽指数分别降低了15.72%、22.41%、29.10%和44.15%,活力指数分别下降了13.03%、31.73%、55.17%和60.23%;株高以对照组的最高,和对照组相比,处理1组—处理4组的株高分别降低了23.17%、44.11%、52.75%、60.59%;叶长以对照组最高,除了处理2组、处理3组之间相比差异不显著外,其余各个小组之间相比均达差异显著性水平(P<0.05);叶宽以对照组的最宽,除了处理3组和处理4组之间相比差异不显著外,其余均达差异显著性水平(P<0.05);根长以对照组最长,且各个试验小组的根长相比均达差异性水平(P<0.05)。试验说明,随着镉金属溶度升高,大豆种子的萌发会受到抑制,萌发所需要的时间加长,而且大豆苗的生长也会受到抑制。

土壤镉暴露对玉米和大豆的生态毒性评估

以中国东北黑土为培养基,通过室内急性毒性实验,采用TrimmedSpearman-Karber方法计算EC50值(半抑制浓度),并分析作物的生物累积系数(BAF),定量化评估了土壤中镉对玉米和大豆的生态毒性及生物有效性.测量终点为种子发芽率、根长和幼茎长.结果表明,土壤镉暴露给农作物带来一定的负生长效应.种子发芽率不是评估土壤镉生态毒性的敏感因子,根生长是敏感的毒性测量终点.镉在植株体内的累积及迁移与作物种类和土壤镉浓度有关.玉米植株体内累积了较大量的镉,而大豆植株体内镉由根向幼茎的迁移较为显著.

不同大豆品种镉毒害效应及耐镉差异性

为探讨不同大豆品种耐镉能力的差异,采用营养液培养,对10个大豆品种的Cd毒害效应及耐Cd差异性进行了研究.结果表明,10个大豆品种添加2.50mg/LCd培养14d后,大豆株高及生物产量均低于对照,不同品种间差异显著,其中湘春豆13、沔1101和本地种下降较少,为抗Cd毒害能力较强的品种.大豆的耐Cd能力与其体内Cd含量及Cd化学形态、根系活力(TTC)、POD活性等密切相关,耐Cd品种表现为:1)单位质量生物产量吸收累积的Cd较其他品种低,Cd在植物体内主要以NaCl提取态形式存在,乙醇和水提取态Cd含量相对较少;2)根系活力相对较弱,吸Cd能力较差;3)Cd胁迫后POD活性增加较缓.

表面活性剂LAS与重金属Cd复合污染对黄豆生长的影响

采用盆栽试验方法,研究了表面活性剂LAS(十二烷基苯磺酸钠)与重金属Cd单一及复合污染对黄豆生长和生理生化指标的影响。结果表明,在单一LAS污染条件下,较低浓度的LAS(≤15mg·L-1)能促进黄豆的生长,较高浓度的LAS(≥50mg·L-1)对黄豆有毒害作用。在单一Cd污染条件下,土壤中Cd浓度为5mg·kg-1和10mg·kg-1时,黄豆的生长受到严重的抑制。在同一Cd污染土壤中,随着灌溉水LAS浓度的升高,黄豆的株高、干重、叶片叶绿素含量和SOD活性都呈先升后降的趋势,当LAS浓度为50mg·L-1时,这些指标的数值最大,而MDA含量随着LAS浓度的升高呈先降后升的趋势。通过这些生长及生理生化指标的测定,可以得知低浓度LAS(≤50mg·L-1)能部分缓解Cd对黄豆的毒害。

Cd胁迫对大豆幼苗异黄酮合成关键酶基因表达的影响

为了研究Cd胁迫对大豆异黄酮含量的影响,分析了Cd胁迫下大豆叶片和根系中异黄酮的积累情况,并通过定量PCR方法分析了根系在100μmol/L CdCl2处理不同时间下异黄酮合成途径中相关酶基因表达的变化。结果表明:大豆叶片中的异黄酮含量随着Cd处理浓度的增加而上升,根系中异黄酮含量在100μmol/L CdCl2处理5 d时显著上升;100μmol/L CdCl2处理24 h时,IFS2(异黄酮合酶)、PAL(苯丙氨酸裂解酶)、C4H(肉桂酸-4-羧化酶)、4CL(香豆酸辅酶A连接酶)、CHS(查尔酮合成酶)、CHI(查尔酮异构酶)和CHR(查尔酮还原酶)的表达量明显上升,并与根系中异黄酮含量的积累呈现一致的趋势,表明Cd胁迫下大豆可以通过提高异黄酮合成相关酶的表达来促进异黄酮的积累从而应对Cd胁迫。

镉胁迫对大豆下胚轴保护酶活性的影响

试验研究了不同浓度(0,5,10,30,50μmol/L)镉胁迫对萌发大豆下胚轴保护酶活性的影响。结果表明:10～50μmol/LCd2+胁迫3～6d促使大豆下胚轴过氧化氢(H2O2)的积累显著增加,同时伴随质膜电解质外渗率和组织自动氧化速率升高;镉胁迫4～6d过氧化氢酶(CAT)和超氧化物歧化酶(SOD)活性降低,而过氧化物酶(POD)活性升高,并且POD活性随着镉浓度的增加而增强。

Cd胁迫对萌发大豆种子中活性氧代谢的影响

以砂培法研究了不同浓度(5、10、30、50μmol·L-1)Cd胁迫对萌发大豆种子中活性氧代谢的影响。结果表明,低浓度(5μmol·L-1)Cd处理下,在萌发初期(1～3d)大豆种子中O2-产生速率、H2O2含量与对照无显著差异,萌发第3d大豆种子中超氧化物歧化酶(SOD)和过氧化氢酶(CAT)活性明显高于对照,萌发第4～6dCd对SOD、CAT活性产生抑制作用,同时MAD含量和种子外渗电导率显著升高;高浓度(10、30、50μmol·L-1)Cd处理下,萌发2～6d种子中O2-产生速率、H2O2含量、MDA含量和外渗电导率显著增加,SOD和CAT活性明显下降;Cd对萌发大豆种子中过氧化物酶(POD)具有激活效应,且随着Cd浓度的增加激活效应逐渐增强。大豆种子萌发受Cd胁迫伤害过程中,活性氧代谢失衡,从而造成膜脂过氧化加剧。