Responses of Antioxidant Enzymes to Chilling Stress in Tobacco Seedlings

Chilling is one of the major abiotic stresses limiting yield and quality of many important crops. For better understanding of chilling stress responses in tobacco （Nicotiana tabacum）, growth rate and antioxidant enzymes of seedlings in 2 tobacco cultivars, viz., MSk326 （chilling sensitive variety） and Honghuadajinyuan （HHDJY, chilling tolerant variety） at chilling temperature （5℃） were studied. The results showed that the relative growth rate in chilling period to that in recovery period was significantly higher in roots than that in shoots for both cultivars, suggesting that shoots growth was more easily affected by chilling stress. Chilling stress increased peroxidase （POD） activity and reduced superoxide dismutase （SOD） activity in shoots of HHDJY, and catalase （CAT） activity was little affected. In the roots of HHDJY, chilling stress increased SOD and CAT activities, and had little effect on POD activity. For MSk326, chilling treatment increased SOD activity in shoots and declined CAT activity in roots. MDA concentration in both varieties was increased under the chilling stress, while it was decreased after seedlings were recovered growth for 4 d at normal temperature （25℃）. It showed that tobacco seedlings might have the capacity of recovering from chilling injury for a short term, The relationship between the growth rate and antioxidant enzyme activity was analyzed by stepwise regression. It was found that there was a close relationship between relative growth rate of tobacco seedlings and CAT activity under chilling stress condition and regression equations containing CAT could be used in predicting seedling growth rate of tobacco under chilling stress condition.     

Hg2+胁迫对小麦幼苗POD、CAT和SOD同工酶的影响（英文）

[Objective] This work was aimed to explore the mechanism of Hg2+ toxicity on plants.[Method]Activities of peroxidase(POD),catalase(CAT)and superoxide dismutase(SOD)were investigated in wheat(Triticum aestivum L.)seedlings under Hg2+ stress at different concentrations.[Result]① There were no obvious effects on the growth of seedlings when the concentration of Hg2+ was lower than 0.10 mmol/L.However,toxic effects on the growth of seedling were observed when the concentration of Hg2+ was higher than 0.10 mmol/L.② Different tissues showed different resistant ability in response to Hg2+ stress.The leaves and roots of wheat seedlings were more insensitive to Hg2+ toxicity.③ CAT was more sensitive to Hg2+ stress compared to POD and SOD.[Conclusion]The toxic effect was related to the concentration of Hg2+(0.10 mmol/L).The higher concentration of Hg2+ could affect the expression of POD,CAT,and SOD isozymes in the leaves,roots of wheat seedlings and germinated seeds,which further affect the normal metabolism of membrane lipid and inhibit the growth of wheat seedlings at last.     

Effects of sodium benzoate on growth and physiological characteristics of wheat seedlings under compound heavy metal stress

In this study, we investigated the effect of exogenous sodium benzoate on wheat seedlings(Yangmai 16) grown under heavy metal stress. The results showed that 2.4 mmol kg~(–1) of heavy metals significantly inhibited growth and delayed emergence of wheat seedlings. Under compound heavy metal stress, application of 2–4 g L~(–1) sodium benzoate significantly increased(P0.01) chlorophyll content and chlorophyll fluorescence parameters F_v/F_m and F_v/F_o of wheat, compared to the control(water treatment). Further analysis showed that application of 2–4 g L~(–1) sodium benzoate alleviated osmotic stress by promoting the accumulation of osmolytes such as soluble proteins and free proline, increased the activity of superoxide dismutase(SOD) and reduced malondialdehyde content(MDA). In contrast, higher concentrations of sodium benzoate solution(6 g L~(–1)) inhibited the growth of wheat seedlings and even caused damage to seedlings. Correlation analysis showed that when the sodium benzoate concentration was in the range of 1.97–3.12 g L~(–1)(2016) and 1.58–3.27 g L~(–1)(2017), values of chlorophyll and its components, root activity, SOD activity, soluble protein, and free proline content were the highest. When the sodium benzoate concentration was raised to 2.59 g L~(–1)(2016) or 3.02 g L~(–1)(2017), MDA content was the lowest. Ultimately, exogenous sodium benzoate(2–4 g L~(–1)) facilitates root development and improves the root activity of wheat seedlings grown under compound heavy metals stress, thereby effectively alleviating the damage of compound heavy metal stress in wheat seedlings.     

Genotypic Difference in the Responses of Seedling Growth and Cd Toxicity in Rice （Oryza sativa L.）

The experiment was carried out to study the genotypic difference in the responses of seed germination, growth and physiological characters of rice seedlings to Cd toxicity. The result showed that the germination was slightly stimulated under low Cd concentration （0.01-1.5 mM Cd）, while severely depressed under higher Cd concentration （2.0 mM）. Rice seedlings exposed to 0.01 mM Cd showed slight increases in plant height, root volume, biomass and chlorophyll concentration. These parameters were significantly reduced when Cd level in the medium was increased to 0.5 mM, and meanwhile corresponding increase in superoxide dismutase （SOD） and peroxidase （POD） activities, and MDA （malondialdehyde） content was observed. However, SOD and POD activities declined when plants were exposed to 1 mM Cd when compared with those under 0.5 mM Cd. Cadmium addition lowered Fe, Cu and Mn concentrations in roots and shoots. There was significant genotypic difference in the response of these parameters to Cd stress. Under Cd stress, Xiushui 110 had the least inhibition of growth and increase in MDA content, higher shoot Cd concentration, and greatest increase in POD and SOD activities, indicating its higher tolerance to Cd toxicity, while Bing 9914 had the greatest reduction of growth, and Zn, Cu, Fe, and Mn contents, but greatest increase in MDA content, and least increase in activities of antioxidative enzymes, indicating its sensitivity to Cd toxicity.     

Antioxidant Defense System in Wheat （Triticum aestivum L.） Seedlings under Heat Stress and Revival Conditions

The present investigation was carried out to investigate the effect of heat stress and revival on some antioxidative enzymes and metabolites in leaves of the wheat （Triticum aestivum L.） seedlings of heat susceptible （cv. WH 147 and HS 277） and heat tolerant （cv. WH 1021 and HW 2045） cultivars. Seven days old seedlings grown at 25 ℃ were exposed to 40 ℃ for 6 h and these seedlings were again brought to 25 ℃. The observations were recorded in the leaves of control, stressed and revived seedlings on 2nd and 4th day of revival. For the selection ofthermo-tolerant cultivars, screening of the thirty-six cultivars was done based on wilting of primary leaf and values of chlorophyll fluorescence. The MDA （malondialdehyde） and H2O2 concentration in leaves of wheat seedlings increased at the high temperature. There was enhancement in the activities of antioxidative enzymes, viz. CAT （catalase）, POX （peroxidase）, GR （glutathione reductase） and APX （ascorbate peroxidase） in leaves of the tolerant and susceptible cultivars under heat stress, however, higher percent increase was observed in tolerant cultivars. Heat stress increased the SOD （superoxide dismutase） activity in tolerant cultivars but activity declined in susceptible cultivars. On revival, the activities of the CAT, POX and GR declined in comparison to stressed seedlings but remained higher as compared to control. Ascorbate peroxidase activity remained higher on 2nd day and 4th day of revival in all the cultivars.     

Effects of Nitrogen Forms on Carbon and Nitrogen Accumulation in Tomato Seedling

Utilization of organic nitrogen （N） is an important aspect of plant N assimilation and has potential application in sustainable agriculture. The aim of this study was to investigate the plant growth, C and N accumulation in leaves and roots of tomato seedlings in response to inorganic （NH4^＋-N, NO3^-N） and organic nitrogen （Gly-N）. Different forms of nitrogen （NH4^＋-N, NO3^--N, Gly-N） were supplied to two tomato cultivars （Shenfen 918 and Huying 932） using a hydroponics system. The plant dry biomass, chlorophyll content, root activity, total carbon and nitrogen content in roots and leaves, and total N absorption, etc. were assayed during the cultivation. Our results showed that no significant differences in plant height, dry biomass, and total N content were found within the first 16 d among three treatments; however, significant differences in treatments on 24 d and 32 d were observed, and the order was NO3^--N 〉 Gly-N 〉 NH4^＋-N. Significant differences were also observed between the two tomato cultivars. Chlorophyll contents in the two cultivars were significantly increased by the Gly-N treatment, and root activity showed a significant decrease in NHa^＋-N treatment. Tomato leaf total carbon content was slightly affected by different N forms; however, total carbon in root and total nitrogen in root and leaf were promoted significantly by inorganic and organic N. Among the applied N forms, the increasing effects of the NH4^＋-N treatment were larger than that of the Gly-N. In a word, different N resources resulted in different physiological effects in tomatoes. Organic nitrogen （e.g., Gly-N） can be a proper resource of plant N nutrition. Tomatoes of different genotypes had different responses under organic nitrogen （e.g., Gly-N） supplies.     

The Effects of Arbuscular Mycorrhizal Fungi on Reactive Oxyradical Scavenging System of Tomato Under Salt Tolerance

The effects of arbuscular mycorrhizal fungi （AMF）, Glomus mosseae, on oxygen radical scavenging system of tomato under salt stress were studied in potted culture experiments. The response of tomato （Lycopersieon eseulentum L.） cultivar Zhongza 9 seedlings with AMF inoculation and control to salt stress （0, 0.5 and 1.0% NaCl solution, respectively） was investigated. The results showed that the salt stress significantly reduced the dry matter content of roots, stems and leaves, and also the leaf area as compared with the control treatment. However, arbuscular mycorrhizal-inoculated （AM） significantly improved the dry matter and the leaf area in the salt-stressed plants. The effect of AMF on dry matter was more pronounced in aerial bromass than in root biomass which might be due to AM colonization. The activities of SOD, POD, ASA-POD, and CAT in leaves and roots of mycorrhizal and non-mycorrhizal treatment of tomato plants were increased and had different rules under different NaCl concentrations （solution of 0, 0.5 and 1% NaCl）, but all enzymes had a rise in the beginning of treatment under salt stress conditions. The AMF did not change the rule of tomato itself under salt stress, but AMF increased these enzyme activities in different levels. The AMF treatment significantly increased SOD, POD and ASA-POD activities in leaves and roots, whereas it had little effects on CAT in root. O2- production rate and MDA content in leaves increased continuously, which showed a positive line correlation with salt stress concentration. O2- production rate and MDA content in tomato plants significantly decreased by AM treatment compared with nonmycorrhizal treatment. In conclusion, AM could alleviate the growth limitations imposed by saline conditions, and thereby play a very important role in promoting plant growth under salt stress in tomato.     

Study on Effect of Age of Seedlings Transplant on the Performance of Tomato （Lycopersicon esculentum） in a Southwestern Nigeria Location

Field trials were conducted at the experimental site of the Department of Plant Science of the University of Ado Ekiti, Nigeria during the 2005 and 2006 cropping season to examine the effects of age of transplanting on the performance of tomato Lycopersieon esculentum L. Establishment count %, plant height stem girth, earliness to flower, and fruit yield were significantly affected by the ages at which the seedlings were transplanted. The 2 and 3 weeks after sowing transplants were identical in performance and gave the highest number of field establishment count, growth increase, and yield. The 4WAS transplants performed better than the 5WAS transplants. It is concluded that a delay in early transplanting of tomato seedlings after 4WAS could lead to a very high reduction in tomato yield in the study area.     

番茄内生细菌的分离及其促生活性研究(英文)

[Objective] The study aimed to investigate the growth-promoting activities of endophytic bacteria from tomato plants.[Method]The endophytic bacteria isolated from different tissues of tomato plants were analyzed for the effects of their growth-promoting activities on the germination and growth of tomato plants.The bacteria with growth-promoting activity were preliminarily identified.[Result]Totally 59 endophytic bacterial strains were isolated from roots and stems of tomatoes,of which 4 showed significantly growth-promoting activity to germination and growth of tomato.The results suggest that these strains are endowed with the potential capability of growth-promoting.[Conclusion]The endophytic bacteria with growth-promoting activity were found among the isolates from tomato plants.This provided a good foundation for utilization of these bacteria with growth-promoting activity.     

Effects of Cu2+ and Cd2+ Stress on Growth and POD Activity of Tomato Seedling

The growth situation and peroxidase (POD) of seedlings of two tomato cuhivars were investigated under the stress of different concentrations of Cu2+ and Cd2+. The toxicity differences of Cu2+ and Cd2+ to tomato seedlings and the corresponding differences between two tomato cultivars were observed through the stress trial with the above two heavy metal ions. The results showed that low concentration of Cu2+ and Cd2+ could promote the growth and could enhance the POD activity of tomato seedlings, while high concentration Cu2+ and Cd2" could inhibit seedling growth and POD activity of tomato seed-lings. Cd2+ functioned more obviously than that of Cu2+, two tomato cultivars also presented difference in response to heavy metal stress.     

Cu2+、Cd2+胁迫对番茄幼苗生长及过氧化物酶活性的影响

笔者以番茄2个种（402,205）为材料,研究不同浓度Cu^2＋、Cd^2＋对番茄幼苗生长及过氧化物酶活性的影响,以期为Cu^2＋、Cd^2＋对番茄的伤害机制提供理论依据。     

Cu~(2+)·Cd~(2+)胁迫对番茄幼苗生长及过氧化物酶活性的影响

利用不同浓度Cu2+、Cd2+处理2个番茄品种的幼苗,研究重金属离子对番茄苗期生长和叶片过氧化物酶(POD)活性的影响,比较Cu2+、Cd2+两种重金属离子对番茄幼苗的毒性差异及2个番茄品种之间的差异。试验结果表明,Cu2+、Cd2+在较低浓度时能够促进番茄幼苗生长,提高POD活性;而随着浓度提高抑制作用明显。且Cd2+的影响比Cu2+明显,2个不同番茄品种间也存在差异。     

Cu2+、Cd2+、Hg2+对玉米幼苗生长和抗氧化酶活性的影响

【目的】研究必需元素Cu²⁺和非必需元素Cd²⁺、Hg²⁺对玉米幼苗生长及抗氧化酶活性的影响,探讨玉米抵抗重金属毒害的机理。【方法】用自来水(CK)及高(1 mmol/L)、中(0.5 mmol/L)、低(0.25 mmol/L) 3个浓度的重金属离子Cu²⁺、Cd²⁺、Hg²⁺溶液滴灌玉米幼苗,处理3 d后测定玉米幼苗根长和叶长、可溶性蛋白和叶绿素含量及超氧化物歧化酶（SOD）、过氧化物酶（POD）的活性,并对根系和叶片中POD同工酶表达的变化进行电泳分析。【结果】与CK相比,3种重金属离子明显抑制玉米幼苗生长,提高根系和叶片中可溶性蛋白含量,对叶绿素含量的影响与其浓度有关。Cu²⁺对玉米根系中SOD活性无明显影响,Cd²⁺和Hg²⁺明显降低了根系中SOD活性。Cu²⁺使玉米幼苗根系中POD活性增强;低浓度Cd²⁺和Hg²⁺使玉米根系中POD活性增强,中、高浓度Cd²⁺和Hg²⁺则使玉米根系中POD活性减弱。重金属对根系中POD同工酶的影响表现为：Cu²⁺无明显影响,Cd²⁺减弱了Rb1和Rb2的表达,Hg²⁺则抑制了Rb1的表达,增强了Rb2的表达,且低浓度Hg²⁺诱导出了Rb3。重金属对叶片中POD同工酶的影响表现为：随着处理浓度的增大,Lb5表达增强,其中Cd²⁺的诱导效果最强;与CK 及Cu²⁺ 和Cd²⁺相比,Hg²⁺完全抑制了Lb6的表达。【结论】Cu²⁺、Cd²⁺、Hg²⁺对玉米生长及SOD和POD活性的影响,与重金属种类和浓度有关,并存在器官特异性。重金属中必需元素和非必需元素都会影响POD同工酶的表达,但作用机理不同。     

利用DH群体研究Cd2+对小麦苗期生长的影响

镉(Cd)是农田土壤重金属污染的主要元素,易被植物吸收,并通过食物链在人体内富集.研究不同浓度的Cd2+胁迫对小麦苗期生长的影响,对小麦防镉污染生产具有重要意义.本文以花培3号和豫麦57两个品种构建的含有168个双单倍体(DH)群体为实验材料,在相同遗传背景和大样本下进行了不同浓度Cd2+胁迫下对小麦苗期生长性状影响的研究分析.结果表明:Cd2+胁迫下小麦幼苗和根系生长受到抑制,浓度越高,抑制作用就越大,DH群体株系间所有性状的方差分析F值达0.01极显著水平,说明存在着基因型差异.在0 mg/L(对照)、40 mg/L和120 mg/L三种浓度Cd2+下各性状之间的相关性也存在着差异,与对照相比Cd2+胁迫下根体积与根平均直径呈现极显著正相关;株高与根平均直径、根平均直径与根表面积、根尖数与茎叶鲜重没有相关性,叶龄与根系总长、根表面积、根体积、根尖数也不再具有相关性,而根系总长与茎叶鲜重、根尖数与茎叶干重之间由极显著水平变为了显著水平.根平均直径与浓度呈极显著正相关,相关系数为0.754,茎叶鲜重、茎叶干重、株高、叶龄、根系总长、根表面积、根体积、根尖数、根鲜重、根干重10个性状与浓度都呈负相关.     

Cu（2＋）、Cd（2＋）、Cr（6＋）胁迫对斑马鱼抗氧化酶活性的影响

[目的]研究Cu2＋、Cd2＋、Cr6＋对斑马鱼抗氧化酶活性影响,探讨重金属对斑马鱼毒性大小。[方法]以斑马鱼为模式生物,采用半静态法对斑马鱼进行驯养和试验,测定Cu2＋、Cd2＋和Cr6＋对超氧化物歧化酶（SOD）、过氧化物酶（POD）和过氧化氢酶（CAT）活性影响。[结果]Cu2＋暴露1d胁迫斑马鱼SOD和CAT为诱导效应,胁迫POD为抑制-诱导-抑制效应,Cu2＋暴露7 d胁迫斑马鱼SOD为诱导效应,胁迫POD和CAT为抑制效应;Cd2＋和Cr6＋暴露1 d和7 d胁迫斑马鱼SOD和CAT均为诱导效应,胁迫POD为抑制效应。且暴露1 d和暴露7 d酶活性变化均显著。[结论]Cu2＋、Cd2＋和Cr6＋单一胁迫斑马鱼抗氧化系统酶活性变化显著,在短时间和低浓度暴露下,Cr6＋毒性作用最显著;在短时间中、高浓度暴露下,Cd2＋毒性作用最显著;长时间暴露时,Cu2＋毒性作用最强,可为重金属污染对水生生物毒性机理研究提供参考。     

Cu~(2+)、Hg~(2+)及其混合胁迫对阿根廷蜈蚣草生理的影响

为寻求水环境中重金属监测的指示植物应用于生产,通过离子溶液浸泡试验,研究Cu~(2+)、Hg~(2+)及其混合胁迫对高等水生沉水植物阿根廷蜈蚣草可溶性蛋白质含量、可溶性糖含量和MDA(丙二醛)含量、CAT(过氧化氢酶)活性等生理生化指标的影响。结果表明:1)可溶性蛋白质和可溶性糖含量随胁迫强度的增加而持续下降,当Cu~(2+)、Cu~(2+)+Hg~(2+)混合处理浓度≤1 mg/L时,可溶性蛋白质含量上升;2)MDA含量与受胁迫强度呈正相关关系;3)在胁迫处理24h内,CAT活性逐渐升高,而后随时间延长活性下降,直至出现抑制现象;4)同浓度处理对阿根廷蜈蚣草生理胁迫强度为Cu~(2+)Hg~(2+)Cu~(2+)+Hg~(2+)。     

Ca2+对Pb2+胁迫下板蓝根种子萌发及幼苗生理特性的影响

为探讨Ca2+缓解Pb2+胁迫的机制,采用培养皿发芽法,研究Pb2+(0、100、500mg/L)胁迫下不同质量浓度的Ca2+(0、80、160、320mg/L)对板蓝根种子萌发及幼苗POD、SOD活性及蛋白质质量分数的影响。结果表明,低质量浓度的Ca2+(80、160mg/L)可缓解Pb2+毒害,显著提高板蓝根种子的发芽率、发芽势、发芽指数、活力指数,促进蛋白质质量分数的增加,提高SOD、POD活性,且Ca2+80mg/L缓解效果最好,缓解能力随Pb2+质量浓度的升高有所下降;高质量浓度的Ca2+(320mg/L)与Pb2+作用,反而抑制板蓝根种子的萌发,幼苗的POD、SOD活性及蛋白质质量分数下降。低质量浓度Ca2+可以显著提高板蓝根的抗性,对Pb2+毒害起缓解作用,高质量浓度的Ca2+与Pb2+对板蓝根起协同毒害作用。     

La3+对Cd2+胁迫萝卜幼苗的防护效应

[目的]为重金属污染植物的生态防御提供参考。[方法]用不同浓度CdCl2（0、1×10^-4、5×10^-4、1×10^-3、5×10^-3mol／L）处理萝卜幼苗,各处理整株喷洒等量工丑（N0,）,溶液（以喷洒等量蒸馏水为对照）,研究镧对铬胁迫下萝卜幼苗的防护效应。[结果]镉胁迫下,萝卜幼苗的株高、主根长、根系活力、叶绿素含量和硝酸还原酶活性均有所下降,质膜透性、脯氨酸含量、过氧化氢酶（CAT）及过氧化物酶（POD）活性均显著升高;喷洒一定剂量（15mg／L）La（NO3）,后,萝卜幼苗的根系活力、叶绿素含量、硝酸还原酶活性均有所升高,质膜透性、脯氨酸含量均有所降低。[结论]适当剂量的稀土元素镧可减轻重金属元素铬对萝卜幼苗的伤害。     

镉胁迫对小麦种子萌发和幼苗生长的影响

以新麦18为材料,研究不同浓度Cd2＋对其种子萌发和幼苗生长的影响。结果表明,低浓度（2mg/L）Cd2＋可促进小麦种子萌发,而高浓度Cd2＋对小麦种子萌发具有抑制作用。随着Cd2＋处理浓度的升高,小麦幼苗叶绿素含量下降,超氧化物歧化酶（SOD）、过氧化物酶（POD）活性升高。但随着Cd2＋处理时间的延长,小麦幼苗SOD、POD活性下降,丙二醛（MDA）和脯氨酸（Pro）含量上升。