铅锌胁迫对凹叶厚朴幼苗生理特性的影响

Effects of lead and zinc on the physiological characteristics of Magnolia officinalis subsp.biloba seedlings

【目的】探究凹叶厚朴对铅锌胁迫的耐受性及生理机制,为将凹叶厚朴作为铅锌污染地区生态修复植物提供可行性依据。【方法】设置不同浓度的铅、锌单一及复合3种胁迫方式处理,分析比较其对铅锌胁迫的光合及生理响应特征。【结果】在Pb^(2+)质量分数高于200 mg·kg^(-1)、Zn^(2+)质量分数高于400 mg·kg^(-1)、Pb^(2+)-Zn^(2+)复合质量分数高于(200+200)mg·kg^(-1)时,凹叶厚朴叶片光合色素合成受到抑制,净光合速率、气孔导度、蒸腾速率逐渐下降;单一铅和铅锌复合胁迫下,叶片净光合速率下降的同时都伴随着气孔导度的下降和胞间CO_(2)浓度的上升,表明非气孔因素是导致凹叶厚朴叶片光合作用下降的主要因素。当Pb^(2+)质量分数低于600 mg·kg^(-1)时,过氧化物酶(POD)和过氧化氢酶(CAT)活性逐渐增加;当Zn^(2+)质量分数低于600 mg·kg^(-1)时,抗氧化酶活性均不断上升;当Pb^(2+)-Zn^(2+)复合质量分数低于(300+300)mg·kg^(-1)时,超氧化物歧化酶(SOD)和CAT活性逐渐上升。3种胁迫方式处理下的丙二醛(MDA)含量均随胁迫质量分数增加不断上升,且显著高于对照。随着Pb^(2+)胁迫质量分数的增加,叶片可溶性糖、可溶性蛋白呈上升趋势,而游离脯氨酸含量在Pb^(2+)质量分数高于600 mg·kg^(-1)时是降低的,但降低幅度小;Zn^(2+)及Pb^(2+)-Zn^(2+)复合胁迫下,可溶性糖和游离脯氨酸含量随胁迫质量分数增大而增加,而可溶性蛋白含量在Zn^(2+)质量分数低于600 mg·kg^(-1),复合质量分数低于(300+300)mg·kg^(-1)时逐渐增大。【结论】在Pb^(2+)、Zn^(2+)质量分数小于600 mg·kg^(-1),Pb^(2+)-Zn^(2+)复合质量分数小于(300+300)mg·kg^(-1)时,凹叶厚朴幼苗可以通过提高抗氧化酶活性及可溶性糖和脯氨酸含量等生理生化过程来应对铅锌胁迫,在高质量分数铅、锌胁迫下植株仍能生长,表明凹叶厚朴幼苗对铅、锌具有较强的耐受性。

【Objective】The purpose of this study was to investigate the tolerance and physiological mechanism of Magnolia officinalis subsp.biloba to lead and zinc stress,to provide a feasible basis for the ecological restoration of Magnolia officinalis in lead and zinc polluted areas.【Method】Three kinds of stress treatments with different concentrations of lead and zinc were set up,and the photosynthetic and physiological response characteristics of Magnolia officinalis to lead and zinc stress were analyzed and compared.【Result】The photosynthetic pigment synthesis of Magnolia officinalis leaves was inhibited,and the net photosynthetic rate,stomatal conductance and transpiration rate were gradually decreased when the mass fraction of Pb^(2+)was higher than 200 mg·kg^(-1),the mass fraction of Zn^(2+)was higher than 400 mg·kg^(-1)and the mass fraction of Pb^(2+)-Zn^(2+)was higher than(200+200)mg·kg^(-1).The decrease in net photosynthetic rate was accompanied by a decrease in stomatal conductance and an increase in intercellular CO2 concentration,indicating that non-stomatal factors were the main factors leading to the decrease in photosynthesis of Magnolia officinalis.When the mass fraction of Pb^(2+)was lower than 600 mg·kg^(-1),peroxidase(POD)and catalase(CAT)activities gradually increased.The activities of antioxidant enzymes increased continuously when the mass fraction of Zn^(2+)was below 600 mg·kg^(-1),and the activities of superoxide dismutase(SOD)and CAT increased gradually when the mass fraction of Pb^(2+)and Zn^(2+)complex was below(300+300)mg·kg^(-1).Under all three stress treatments,the malondialdehyde(MDA)content increased with the increase of stress mass fraction,which was significantly higher than that of the control.With the increase of Pb^(2+)stress mass fraction,the soluble sugar and soluble proteins in leaves showed an increasing trend,while the free proline content was slightly decreased when the Pb^(2+)mass fraction was higher than 600 mg·kg^(-1).Under Zn^(2+)and Pb^(2+)-Zn^(2+)combined stress,the contents of soluble sugar and free proline increased with the increase of stress mass fraction,while the soluble protein content gradually increased when the Zn^(2+)mass fraction was below 600 mg·kg^(-1)and the complex mass fraction was below(300+300)mg·kg^(-1).【Conclusion】This study shows that when the mass fraction of Pb^(2+)and Zn^(2+)is less than 600 mg·kg^(-1)and the mass fraction of Pb^(2+)-Zn^(2+)is below(300+300)mg·kg^(-1),Magnolia officinalis seedlings can cope with lead and zinc stress by increasing antioxidant enzyme activities,soluble sugar and proline contents and other physiological and biochemical processes.The plants could still grow under high mass fractions of lead and zinc,indicating that Magnolia officinalis seedlings have a strong tolerance to lead and zinc stress.