凤眼莲、大薸对铀胁迫的生理生化响应

Physiological and biochemical responses of Eichhornia crassipes and Pistia stratiotes induced at uranium stress

为探讨凤眼莲和大薸在铀胁迫下的生理生化响应,通过Hoagland水培试验,研究了不同铀质量浓度处理对凤眼莲和大薸的光合色素质量比、抗氧化酶（SOD、CAT、POD）活性、丙二醛（MDA）含量、游离脯氨酸质量比的影响,以及凤眼莲和大薸对铀的富集能力。结果表明：随铀处理质量浓度增大,凤眼莲和大薸体内铀质量比增加,在50 mg/L铀胁迫下,两者体内铀的质量比达1 550.2 mg/kg和963.0mg/kg;在铀的质量浓度为0.1 mg/L时,凤眼莲和大薸的光合色素质量比无显著变化（p〉0.05）,随着铀质量浓度的增大,光合色素质量比持续降低;在铀的质量浓度为0.1~1 mg/L时,抗氧化酶系统在凤眼莲和大薸缓解较低质量浓度铀胁迫所引起的膜脂过氧化中发挥了重要作用;凤眼莲对铀的耐受能力要强于大薸;高质量浓度（20 mg/L和50 mg/L）铀处理下,凤眼莲和大薸抗氧化酶活性受到抑制;作为渗透调节物质,二者游离脯氨酸质量比均高于对照。

The present paper intends to introduce our study of the physiological and biochemical responses of Eichhornia crassipes and Pistia stratiotes induced at the uranium stress.For our research purpose,we have conducted a Hoagland hydroponic experiment to study the short-duration（8 d） power-accumulation of uranium by using E.crassipes and P.stratiotes at different uranium concentrations.To be exact,our experiments are designed to study the physiological and biochemical responses of Eichhornia crassipes and Pistia stratiotes to the photosynthetic pigment content,superoxide dismutase activity,catalase activity,peroxidase activity,malondialdehyde（MDA） and free proline content of E.crassipes and P.stratiotes under uranium stress.The results of our experiment show that the body uranium content was about 1 550.2 mg/kg and 963.0 mg/kg under 50 mg/L uranium stress,respectively,with the uranium accumulation more in their roots than shoots.As the uranium stress concentration increased,the BCF of both the plants tended to decrease.The BCF of E.crassipes was found higher than P.stratiotes,which implies that the accumulation power of E.crassipes turned to be stronger than P.stratiotes.However,no significant（p0.05） changes were found with the photosynthetic pigment content of E.crassipes and P.stratiotes under the uranium stress of 0.1 mg/L.Nevertheless,with the increase of the concentration,the content would continue to decrease.Under the uranium stress of 0.1-1 mg/L,the activity of antioxidant enzymes would be found more and more stronger.Nevertheless,the MDA content level getting lower means that the antioxidant enzymes tends to play an important role in alleviating lipid peroxidation induced by the uranium stress.For example,when uranium stress remains under 5 mg/L,the antioxidant enzymes＇ activity of E.crassipes would be at higher level.But when the MDA content grew lower,the P.stratiotes would go to opposite,which implies that E.crassipes could tolerate higher concentrations than P.stratiotes.Under higher concentrated（20 mg/L and 50 mg/L） uranium stress,the activity of antioxidant enzymes would be found inhibited,which may induce ROS and H2O2 massive accumulation and then the MDA content would grow.As an important osmoregulation material,free proline content tended to be found greater than that of the contrast and in turn would play a role in adjusting osmotic under uranium stress and effectively inhibit both the plants from getting harmed or damaged.