Arbuscular mycorrhizal fungi (AMF) are important in the phytoremediation of cadmium (Cd). Improving photosynthesis under Cd stress helps to increase crop yields. However, the molecular regulatory mechanisms of AMF on photosynthetic processes in wheat (Triticum aestivum) under Cd stress remain unclear. This study utilized physiological and proteomic analyses to reveal the key processes and related genes of AMF that regulate photosynthesis under Cd stress. The results showed that AMF promoted the accumulation of Cd in the roots of wheat but significantly reduced the content of Cd in the shoots and grains. The photosynthetic rates, stomatal conductance, transpiration rates, chlorophyll content, and accumulation of carbohydrates under Cd stress were increased by AMF symbiosis. Proteomic analysis showed that AMF significantly induced the expression of two enzymes involved in the chlorophyll biosynthetic pathway (coproporphyrinogen oxidase and Mg-protoporphyrin IX chelatase), improved the expression of two proteins related to CO2 assimilation (ribulose-1,5-bisphosphate carboxylase and malic enzyme), and increased the expression of S-adenosylmethionine synthase, which posi-tively regulates abiotic stress. Therefore, AMF may regulate photosynthesis under Cd stress by promoting chlorophyll biosynthesis, carbon assimilation, and S-adenosylmethionine metabolism.

为研究丛枝菌根真菌(AMF)是否通过对镉(Cd)胁迫小麦褪黑素(MLT)代谢的调节作用来增强小麦Cd耐性,以小麦和摩西球囊霉为试验材料,采用土培方法,研究Cd胁迫下接种AMF对小麦MLT代谢的调节作用.结果显示,Cd胁迫下接种AMF处理与同浓度Cd胁迫处理相比,小麦叶片5-羟色胺(5-HT)、5-甲氧基色胺(5-MT)、MLT及2-羟基褪黑素(2-HMT)含量均有不同程度的增加,MLT合成相关酶及分解相关酶的活性均有不同程度的提高,MLT的合成酶基因TaASMT1、TaASMT2、TaCOMT、TaSNAT及MLT的分解基因Ta2-ODD的表达水平均有不同程度上调.表明AMF可以通过上调Cd胁迫小麦内源MLT代谢相关基因表达水平来提高相应酶的活性,促进MLT的合成,同时加速MLT分解为2-HMT,缓解Cd胁迫造成的氧化伤害,增强小麦的Cd耐性.

为了探究丛枝真菌对镉(Cadmium,Cd)胁迫小麦的修复作用,以小麦(Triticum aestivum L.)品种百农207和摩西球囊霉菌(Glomus mosseae,Gm)为材料,采用土培试验方法,研究了丛枝真菌对Cd胁迫小麦幼苗类黄酮含量、一氧化氮(Nitric oxide,NO)含量、过氧化氢(Hydrogen peroxide,H2 O2)浓度、硝酸还原酶(Nitrate reductase,NR)活性的影响.结果显示,5和10 mg·kg-1 Cd胁迫接种丛枝真菌小麦幼苗与同质量浓度Cd胁迫小麦幼苗相比,类黄酮含量上升,但差异不显著;NR活性显著上升,分别是5和10 mg·kg-1 Cd胁迫小麦幼苗的1.94,2.03倍;NO含量显著上升,分别比5和10 mg·kg-1 Cd胁迫小麦幼苗提高了50.70％,35.96％;H2 O2含量显著下降,分别比5和10 mg·kg-1 Cd胁迫小麦幼苗下降了34.77％,36.07％.结果表明,接种丛枝真菌可以通过提高类黄酮、NO含量和NR活性,降低Cd胁迫产生的过量活性氧,缓解Cd胁迫造成的氧化伤害.

以小麦(Triticum aestivum L.)为材料,采用土培试验,研究了接种丛枝菌根真菌对镉(Cd)胁迫小麦幼苗超氧阴离子产生速率、球囊霉素相关土壤蛋白(GRSP)、根内Cd含量、植物螯合肽(PC)含量及植物螯合肽合成酶(PCS)活性的影响.结果表明,Cd胁迫未接种丛枝菌根真菌造成小麦叶片超氧阴离子产生速率、PC含量、PCS活性及根内Cd含量显著增加,且随着胁迫质量分数的增加而极显著上升;胁迫质量分数下接种丛枝菌根真菌较未接种相比,小麦叶片内超氧阴离子产生速率、PC含量和PCS活性降低,根际土壤GRSP及根内Cd含量则极显著升高.本研究表明,接种丛枝菌根真菌可通过土壤GRSP鳌合作用将部分Cd固定在土壤中,同时增加根系中Cd的含量,缓解Cd胁迫对叶片造成的氧化伤害,解除Cd的部分毒性.

对小麦几丁质酶基因家族成员进行鉴定,并对其基因结构、保守基序、染色体分布、系统进化及禾谷镰刀菌胁迫下的表达水平进行分析,为进一步研究几丁质酶基因在小麦应答各种生物胁迫中的作用和在抗病分子育种中的应用奠定基础.结果表明,从小麦基因组中共鉴定到159个几丁质酶基因,分布在21条染色体上;小麦几丁质酶基因家族成员分为5类,隶属于GH-18和GH-19两个亚家族.GH-18亚家族包括Ⅲ、Ⅴ类,分别含有34、48个基因;GH-19亚家族包括Ⅰ、Ⅱ、Ⅳ类,分别包含52、13、12个基因.同一亚家族的成员聚类在同一分支上,并且具有相似的外显子-内含子基因结构和保守基序.在被禾谷镰刀菌侵染后,4个小麦品系中几丁质酶基因家族一些成员的表达均显著上调.

To investigate the regulation of arbuscular mycorrhizal fungi (AMF) on photosynthesis of wheat under cadmium (Cd) stress,the pot-experiment was carried out with wheat (Triticum aestivum L.) bainong 207 and Glomus mosseae (GS) as materials. Effects of arbuscular mycorrhizal fungi on photosynthetic rate,conductance to H2O,transpiration rate,intercellular CO2 concentration,chlorophyll fluorescence,chlorophyll contents,trace element iron (Fe) ,magnesium (Mg) ,zinc (Zn) and cadmium(Cd) contents in wheat leaves were studied under Cd stress. The results showed that the photosynthetic rate,transpiration rate,conductance to H2O were increased by 11. 16％,21. 76％ and 14％,chlorophyll fluorescence,chlorophyll content increased 5. 56％ and 6. 56％,Fe,Mg and Zn contents increased 6. 63％,20％ and 4. 29％,the content of Cd and intercellular CO2 concentration decreased 18. 50％ and 17. 62％ under 5 mg·kg - 1 Cd stress,respectively. Under 10 mg·kg - 1 Cd stress,the photosynthetic rate,transpiration rate,conductance to H2O were increased by 28. 65％, 41. 25％ and 50％; chlorophyll fluorescence,chlorophyll content were increased by 1. 43％ and 15. 33％; Fe,Mg and Zn contents by increased were 7. 81％,30. 77％ and 9. 74％,but the content of Cd and intercellular CO2 concentration decreased 32. 20％ and 6. 45％,respectively. Therefore, inoculation of AMF could alleviate Cd stress and increased the chlorophyll content of wheat to enhance photosynthesis.

To study effects of inoculation arbuscular mycorrhizal fungi with tobacco on detoxification Pb stress,a pot experiment was carried out with tobacco (Nicotiana tabacum L.) and Glomus intraradice.The result showed that,under Pb stress,after inoculation Glomus intraradice with tobacco,Pb contentdecreased in leaves,but significant increase in roots.The H2O2 content and production rate of superoxide aninwere decreased significantly,and the activity of SOD,CAT,APX,POD and MDA content decline accordingly.As glyoxalase I activity was enhanced and glutathione content increase in the leaves,the potent cytotoxic compound methylglyoxal decreased.The result indicated that inoculation arbuscular mycorrhizal fungi with tobacco could reduce oxidative stress and content of Pb in leaves,and consequently raise the quality of tobacco.

以烟草(Nicotiana tabacum L.)品种中烟100为材料,采用盆栽试验,研究Pb胁迫下接种与未接种摩西球囊霉菌(Glomus mosseae,GM)对烟草的形态变化、叶绿素含量、菌根侵染率、球囊霉素(GRSP)含量、Pb含量(包括土壤残留、根、烟叶和球囊霉素中)等的影响,以探讨Pb胁迫下GM对烟草的解毒效应.结果表明,接种GM后叶片变绿;叶绿素a(Cht a)和叶绿素b(Chl b)含量升高,Chl a/Chl b值显著升高;接种GM后菌根侵染率为32.72％和26.17％,显著地提高了GRSP含量;与同质量分数Pb胁迫未接种组相比,接种GM后根和土壤中残留Pb含量显著增加,而烟叶中Pb含量极显著减少,且下部叶＞中部叶＞上部叶.

For better use of tea plant (Camellia sinensis) flower resources, biochemical components and contents of eight tea cultivars flowers were investigated. Volatile aromatic compounds were extracted by simultaneous distillation and solvent extraction (SDE) and determined using Gas Chromatography (GC) and Gas Chromatography/Mass Spectrometry (GC-MS). The contents of tea polyphenols, amino acids, caffeine, soluble sugars and soluble proteins was assayed by colorimetric method with ferrous tartrate, ultraviolet spectrophotometric method, anthrone colorimetric method and coomassie brillient blue method, respectively. Among the eight cultivars flowers there were big difference in contents and numbers of volatile aromatic compounds. The greatest numbers of volatile aromatic compounds in flowers was 50, and the least numbers of volatile aromatic compounds in flowers was 9. The major constituents of volatile aromatic compounds in flowers included alkanes, alcohols, esters, ketones, aldehydes and alkenes. Acetophenone and tricosane were found in each cultivar flowers. However, The content of acetophenone, 2-heptanol, (S)-, 1,6-octadien-3-ol, 3,7-dimethyl-, 1,2-benzenedicarboxylic acid, mono(2-ethylhexyl) ester and di-n-octyl phthalate were higher in some flowers. The result also indicated that tea flowers were rich in soluble sugars and soluble proteins.

Potted tea trees were inoculated with arbuscular mycorrhizal fungi(Glomus intraradices) under Pb stress to investigate the effects of inoculation on detoxification apacity of tea tree. Methods including acetate ink staining,Coomassie brilliant blue,inductively coupled plasma(ICP-MS) and UV spectrophotometry method respectively were used to determine tea tree root colonization rate of mycelium,content of Glomalin-related soil protein(GRSP),Pb content in tea tree roots,leaves,soil and GRSP,and antioxidant enzyme activity of leaves. The results showed that AMF inoculation rate in tea tree roots was 60.13%,tea tree biomass and 100-bud weight increased significantly. The total GRSP content also increased remarkably after inoculation with AFM. For GRSP chelated Pb in soil,the bioavailability of Pb in soils reduced greatly. For the total contents of Pb in roots and leaves decreased,and more Pb deposited in roots after inoculation,the Pb contents in leaves decreased significantly, and the antioxidant enzyme activity correspondingly reduced.

以小麦（Triticum aestivum）矮抗58为材料,采用0.1mmol/L的外源水杨酸（SA）处理小麦叶片,以清水为对照,通过Western blotting蛋白质印记技术和叶绿素荧光分析,研究了高温强光胁迫（38℃和1600μmol m-2s-1）对小麦叶绿体Deg5蛋白酶、D1蛋白和叶绿素荧光参数的影响及SA的调节作用。结果表明,高温强光胁迫导致小麦叶绿体Deg5蛋白酶、D1蛋白含量和PSⅡ最大光能转化效率（Fv/Fm）降低,原初荧光（Fo）升高。和对照相比,外源SA处理可维持较高的Deg5蛋白酶、D1蛋白、Fv/Fm水平和较低的Fo。说明外源水杨酸可减轻高温强光对Deg5蛋白酶和D1蛋白的损伤,维持较强的PSⅡ功能。

We adopted a proteomics approach to identify and analyze the differential expression of maize root proteins associated with abscisic acid (ABA) regulation under combined drought and heat stress. Using mass spectrometry, we identified 22 major proteins that were significantly up-regulated under combined drought and heat stress. These 22 proteins were classified into 6 functional categories: disease/defense (8), metabolism (3), cell growth/division (3), signal transduction (2), transporters (2) and unclassified (4). Our previous reports showed that ABA regulates the expression of several small heat-shock proteins (sHSPs) in maize leaves subjected to the combination of drought and heat stress; however, no sHSPs were identified among the root proteins up-regulated in this study. RT-PCR and western blot analyses were used to identify six known sHSPs. The maize roots were pretreated with 100 μM of ABA, and subsequently, the expression of the 22 up-regulated proteins and 6 sHSPs was examined. 11 proteins were up-regulated in an ABA-dependent manner, 13 proteins were up-regulated in an ABA-independent manner, and 4 proteins were up-regulated but inhibited by ABA. The up-regulated proteins are interesting candidates for further physiological and molecular investigations of combination stress tolerance in maize.

ABA, H2O2 and Ca2+ play critical roles as signals in the adaptive responses of plants to water and other stresses. They accumulate in plant cells under water and other stresses and induce changes in stress-related gene expressions. CIPKs, protein kinases associated with a calcineurin B-like calcium sensor, play a role in the regulation of stress gene expression in plants. However, it is still unclear whether ABA and H2O2 are key inducers that regulate the changes in CIPK expressions under water stress. In this study, five stress-inducible CIPKs in maize were retrieved from Database. They were designated as ZmCIPK1, 3, 8, 17 and 18, based on their homologies with known CIPK sequences. The expressions of the five ZmCIPKs in maize leaves and roots were analyzed and found to be regulated by PEG, CaCl2, ABA and H2O2 to different extents. Moreover, the effect of ABA and H2O2 on the expressions of ZmCIPKs under water stress was in an organ-dependent manner.

Using two popcorn inbred lines and six normal corn inbred lines belonging to Reid heterotic group,twelve F1 crosses and their F2 populations were developed.The F1 performance,heterosis,F2 performance and segregation characteristics,and their correlations with parent lines were analyzed for eight ear-kernel characters,including ear length,ear diameter,ear row number,kernel number per row,100 grain weight,ear weight,ear grain weight and kernel rate.The results showed that great differences existed among crosses in F1 performance,mid-parent heterosis(MH) and over-high parent heterosis(HH),and mean value F2M,range,variation coefficient and hetrosis decreasing rate(HDR) in F2 populations,reflecting obvious genetic background effects.All traits showed normal distributions in F2 populations,with transgress segregations beyond two parents.For traits with low heterosis,such as ear row number,kernel rate and ear diameter,F1 performance and kernel rate could be predicted according to parent values,while it was unsuitable for traits with high heterosis,such as ear weight,ear grain weight and 100 grain weight.Besides ear row number and kernel rate,significant positive correlations were observed between F1 with F2M,MH and HH,and among F2M,MH and HH.However,they were all negatively correlated with HDR.Three crosses,R2×N04,R4×N10 and R5×N10,were chosen as much better crosses both in genetic mapping and in improvement for ear-kernel characters in popcorn breeding.

In combination with the actual situation of the experimental teaching of plant biotechnology of Henan agricultural university,being aimed at the weaknesses of the experimental teaching of plant biotechnology,it was given of some advices to improve and strengthen the train of experimental skill;it was discussed of the content,the implementation method and conditions of the creative experimental teaching,and of the high-quality personnel training mode of the combination of creative experiment and research projects.

Tobacco(Nicotiana tabacum L.) seedlings were used to evaluate the effects of exogenous Cd2+ on hormone levels,photosynthetic and fluorescent characteristics.Seedlings with six leaves and same height were hydroponically cultivated in Hoagland′s nutrient solution for 15 d.The seedlings were aerated 3 h per day and the nutrient solution was renewed every 5 d.Afterwards,Cd(NO3)2 was added to the nutrient solution at 0,5,25 and 50 mg/L,respectively(calculated as pure Cd2+).After Cd2+ treatment for 3 d,the Cd2+ contents in leaves were determined with inductively coupled plasma atomic emission spectrometer.The levels of endogenous phytohormones including indoleacetic acid(IAA),gibberellic acid(GA3),abscisic acid(ABA) and zeatin(Z),were assayed with enzyme-linked immunosorbent assay(ELISA).The activities of indoleacetic acid oxidase(IAAO),photosynthetic performance and chlorophyll fluorescent characteristics were measured.Our results showed that the contents of Cd2+ in leaves significantly increased with the increase of exogenous Cd2+ concentration,the activities of IAAO decreased at Cd2+ 5 mg/L,but increased at higher concentrations of exogenous Cd2+.At Cd2+ 50 mg/L,the activity of IAAO increased by 101.71% comparison with the control.Both of the contents of IAA and GA3 increased at Cd2+ 5 mg/L,but decreased with the increase of exogenous Cd2+ concentration.At 50 mg/L Cd2+,the contents of IAA decreased by 34.10%,the contents of GA3 decreased by 39.69%,while the contents of ABA gradually increased with Cd2+ concentration increase.At 50 mg/L Cd2+,the contents of ABA increased by 61.84% comparison with the control.However,the contents of Z sharply decreased with the increase of Cd2+ concentration,and the contents of Z decreased by 75.35% at 50 mg/L Cd2+.Moreover,the contents of chlorophyll a and b and carotenoid decreased significantly with the increase of exogenous Cd2+ contents.At 50 mg/L Cd2+,chlorophyll a and b and carotenoid declined by 34.80%,55.80% and 73.77%,respectively,comparison with the control.All photosynthetic parameters such as net photosynthesis rate(Pn),stomatal conductance(Gs),intercellular CO2 concentration(Ci),transpiration ratio(Tr) decreased with the increase of Cd2+ concentration in the nutrient solution.The fluorescent parameters including PSⅡ potential activity(Fv/Fo),maximal efficiency of PSⅡ photochemistry(Fv/Fm),efficiency of PSⅡ photochemistry(ФPSⅡ),photochemical quenching coefficient(qP) decreased with the increase of exogenous Cd2+.Besides,variable chlorophyll fluorescence(Fv) and maximum chlorophyll fluorescence(Fm) decreased sharply.Pn,Gs,Ci and Tr decreased by 47.59%,66.67%,28.94% and 60.82% respectively,at 50mg/L Cd2+.It suggested that Cd2+ stress disturbed the balance of phytohormone levels in tobacco leaves,and caused the decrease of photosynthetic capacity of tobacco leaves.

A natural hybrid species in Petrocosmea named Longianthera in Yanshan County, Yunnan Province is confirmed for the first time based on molecular and morphological evidence. The character count procedure of the variable characters show that Longianthera populations are characteristic of the intermediate morphological traits between its putative parents Yanshan and Petrocosmea martinii. The nuclear ribosomal internal transcribed spacer region and three chloroplast regions of matK, trnL-F, and trnT-L are sequenced in the putative hybrid and the related species. Both alignment of DNA sequences and the phylogenetic trees could exclude all the other species in Petrocosmea as the parental species except for Yanshan and P. martinii. Eight haplotypes in the 31 internal transcribed spacer sequences and six haplotypes in 42 cpDNA sequences were found from 14 individuals of Longianthera populations. The analyses of DNA sequences, haplotypes, and phylogenetic trees indicate that Longianthera is likely a hybrid species between its putative parents Yanshan and P. martinii, in which Yanshan might be the most possible maternal parent. Several factors may contribute to the natural hybridization between these two parental species in Petrocosmea, such as the overlapped geographic distribution, habitats, flowering periods, and shared pollinators. Finally, the new species of Yanshan and the natural hybrid species of Longianthera are described.

Membrane proteins are involved in many functions due to their cellular locations. Although the effect of drought on plants has been extensively studied, little is known about the changes of membrane proteome in plants under drought conditions. We used gel-based proteomics to study the effect of drought on membrane protein expression in maize (Zea mays L.) plants. Moderate drought stress was applied by 16% (w/v) polyethylene glycol (PEG) treatment of maize seedlings for 8 h. Membrane proteins were extracted from membrane fraction of leaf tissues and separated by two-dimensional electrophoresis followed by matrix-assisted laser-desorption ionization time of flight mass spectrometry. Seventeen protein spots were up-regulated and 18 were down-regulated in response to PEG stress. Hydropathicity (gravy) analysis indicated that 8 spots were hydrophobic and 26 spots were hydrophilic. The identification of proteins indicated that these PEG responsive proteins played diverse functions. Furthermore, the prediction of subcellular localization suggested that 25 spots located in chloroplast, 2 in cytoplasm, while others had other location. Therefore, PEG-responsive membrane proteins are mainly from chloroplasts, which are very sensitive in response to drought stress. Besides, the suitability of the present extraction method for membrane proteins was discussed in the text.

Cadmium (Cd2+) is one of the major widespread environmental pollutants, and can cause serious problems to all organisms. Lead (Pb2+) is another wide spread dangerous heavy metal. Tobacco is a popular growing economic crop in China. Most tobacco growing region soils contain excessive Cd2+ and Pb2+. To assess anatomic changes of tobacco roots under Cd2+, Pb2+, and Cd2++Pb2+ chronic stress, a pot experiment was carried out in field. The tobacco seedlings with 6 leaves were transplanted to pots in which soil was placed. The amounts of Cd2+ added to soil were 0, 3, 6, 10, 30, 60, and 100 mg kg(-1) dry soil. The amounts of Pb2+ added to soil were 0, 150, 300, 450, 600, 750, and 1 000 mg kg(-1) dry soil. The amounts of Cd2++Pb2+ added to soil were 0+0, 3+150, 6+300, 10+450, 30+600, 60+750, and 100+1000 mg kg(-1) dry soil. The contents of Cd2+ and Pb2+ in root systems were determined by inductively coupled plasma, and the anatomical structure was studied by method of paraffin sectioning. The results revealed that the amounts of exchangeable Cd2+ and Pb2+ and carbonate bound Cd2+ and Pb2+ in soil increased with the amounts of Cd2+ and Pb2+ added to soil, and the contents of both Cd2+ and Pb2+ in roots were significantly increased along with stress time and the amounts of Cd2+ and Pb2+ added to soil. The growing of tobacco in Cd2+ and Cd2++Pb2+ polluted soil for 50, 100, and 150 d resulted in some abnormal external morphological and anatomical changes in ripe region of lateral roots. All the abnormal roots had abnormal vascular cylinders, and the ratio of abnormal external morphological and anatomical changes of roots positively correlated with the Cd2+ contents in roots and stress time. While, there were no abnormal external morphological and anatomical changes of roots under Pb2+ stress. It was suggested that Cd2+ stress could cause abnormal anatomic changes of roots, but Pb2+ stress could not.

Cadmium(Cd) is one of major environmental pollutants mainly emanating from mining,industrial trash,anthropogenic activity and use of agro-chemicals.Even in trace concentrations,Cd can cause serious problems to all organisms.In most plant species,Cd accumulated in the roots and was mainly retained in insoluble and soluble forms.Cd inhibited root growth,damaged root hair and root tips by modifying lipid composition of root plasma membrane,increasing the levels of lipid peroxidation.However,it is still unclear about the effect of Cd on the changes in superoxide anions and phytohormone levels,antioxidative capability of CAT,APX and GR in tobacco(Nicotiana tabacum L.) roots.In the present study,the contents of superoxide anions,soluble proteins,phytohormones,the levels of antioxidative capability and lipid peroxidation in roots were determined.Tobacco seedlings with six leaves and same height were cultivated hydroponically in pots containing Hoagland' s nutrient solution.After 15d Cd(NO3) 2 was added to nutrient solution at 0,25,and 50 mg/L(calculated as Cd).Each treatment was replicated three times.The seedlings were aerated 3 h everyday.Root tip segments(3 cm) were used to determine the content of Cd 0.1g dried root samples were ground and the powder was digested with a mixture of HNO3 + HCl + HClO4 3:2:1.5).Samples were evaporated to dry on a plank heated by electricity at 300℃.The elements were extracted with 10% HCl.The samples were put in inductively coupled plasma to determine content of Cd.The content of superoxide anions was assayed according to the method of colorimetry;The content of soluble protein and the activity of GR and APX was determined with UV spectrophotometer;The activity of SOD was determined according to the method of nitroblue tetrazolium;The activity of CAT was determined according to visible spectrophotometry;The content of MDA was determined according to the method of thiobarbituric acid reaction;The activity of POD was determined according to colorimetry;The level of phytohormones was assayed according to the enzyme-linked immunosorbent assay.The results showed that the content of superoxide anions increased with the concentration of Cd.The content of soluble protein increased at 5mg/L of Cd,but decreased at higher Cd concentration.Activities of SOD,CAT and APX increased at 5mg/L Cd,but decreased at higher Cd concentration.Activities of POD and GR increased at the 5-25mg/L range of Cd,then decreased at 50 mg/L of Cd,but was still higher than the control.The content of MDA increased with concentration of Cd.Activity of IAA oxidase increased at 5mg/L of Cd,but decreased with the increase of Cd concentration.The content of IAA and GA at 5mg/L of Cd,but decreased at higher Cd concentrations.With Cd concentration increasing,the content of ABA gradually increased,while the content of ZR sharply decreased.This study will help us to further understand Cd toxicity to tobacco roots.