作 者 ：袁祖丽,吴中红
期 刊 ：生态学报 2010年 30卷 15期 页码：4109~4118
Keywords:cadmium, tobacco, roots, antioxidative capability, phytohormones,
摘 要 ：采用水培试验，研究了镉胁迫对烟草(Nicotiana tabacum)根内的超氧阴离子含量、可溶性蛋白质含量、抗氧化系统SOD、POD、CAT、APX、GR活性、膜质过氧化水平及激素IAA、 ABA、GA3、ZR含量的影响。结果显示烟草根中的超氧阴离子含量随着镉浓度增大而升高；镉浓度为5mg/L时，可溶性蛋白质含量增加，但随着镉浓度增加，可溶性蛋白质含量急剧下降；SOD、CAT、APX 活性在镉浓度为5mg/L时上升，但随着镉浓度升高其活性下降；POD，GR活性在镉浓度为5-25mg/L时上升，在镉浓度为50mg/L时下降，但仍高于对照；MDA含量随着镉浓度增加而升高；IAA氧化酶活性在镉浓度5mg/L时下降，但随着镉浓度的升高而降低；IAA含量在镉浓度为5mg/L时上升，但随着镉浓度增加，IAA氧化酶活性升高，导致IAA含量逐渐下降；镉胁迫对烟草根中ABA合成表现为促进作用；GA3含量在镉浓度为5mg/L时上升，但随着镉浓度的增加其含量逐渐下降；ZR含量在镉胁迫下迅速减少。
Abstract: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.
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