圆叶决明对镉胁迫的生理响应

圆叶决明是我国20世纪80年代从澳大利亚引进的豆科牧草,适合亚热带地区广泛种植。为探明圆叶决明的耐镉性,本文采用添加外源有效态镉的土壤盆栽试验方法,研究不同浓度(0,1,2,4,8 mg/kg)镉胁迫对圆叶决明CIP86134生长发育及其生理响应机制。结果表明,镉胁迫抑制圆叶决明的生长发育,降低其生物产量,且随镉浓度的升高,抑制作用加强。当镉处理浓度为4 mg/kg时,地下部、地上部生物产量与对照比显著下降,分别为对照的59.69%和63.77%。镉胁迫抑制圆叶决明叶绿素a、叶绿素b和类胡萝卜素的合成,镉浓度升高,叶绿素含量逐渐降低,处理之间达显著差异水平。镉处理浓度为12 mg/kg时,SOD、POD、CAT 3类保护酶协调一致,圆叶决明生长正常,地下部、地上部生物产量与对照比差异不显著;镉浓度升高至4 mg/kg,SOD酶活性降低,MDA含量升高,POD和CAT酶被诱导激活,缓解了镉胁迫对圆叶决明的伤害,生物产量虽显著下降,但未中毒死亡;镉浓度升高至8 mg/kg时,MDA含量显著增加,细胞保护酶系统失调,圆叶决明至收获时全部干枯死亡。圆叶决明吸收的镉主要积累在地下部,迁移系数仅为0.1520.234。在供试土壤添加外源有效态镉的条件下,圆叶决明能忍耐2 mg/kg以下的镉胁迫,可作为南方红壤地区矿山镉污染土壤的生态修复植物类型。

Physiological response of Chamaecrista rotundifolia to cadmium exposure

Chamaecrista rotundifolia ,introduced from Australia in the 1980s is a leguminous forage widely cul-tivated in subtropical regions.The effects of cadmium (Cd)exposure on the growth and physiological charac-teristic of C.rotundifolia were studied at different Cd concentrations (0,1,2,4,8 mg Cd/kg dry soil)using a pot experiment.When C.rotundifolia was exposed to a Cd concentration of 1-2 mg Cd/kg soil,the protec-tive enzymes superoxide dismutase (SOD),peroxidase (POD),and catalase (CAT)were all produced and C. rotundifolia growth was normal.There was no significant decrease in underground or aboveground biomass, compared with the controls.When C.rotundifolia was exposed to 4 mg Cd/kg soil,SOD activity was reduced, while the content of the oxidative stress marker malondialdehyde (MDA)increased.However,the enzymes POD and CAT were activated.Therefore,there was some alleviation of Cd stress.Although no tissue death was observed,at the Cd concentration of 4.0 mg/kg,the values for underground and above ground biomass were reduced by 59.69% and 63.77%,respectively,compared with the control.When C.rotundifolia was ex-posed to 8 mg Cd/kg soil,the MDA content increased significantly,the cell protective enzyme system was im-balanced,and all plants were dead when harvested.The synthesis of chlorophyll a,chlorophyll b and carote-noids was inhibited by Cd exposure,and the inhibitory effect increased with increasing Cd concentration.The Cd accumulated mainly in the underground organs of C.rotundifolia,and the translocation factor was only 0.152-0.234.In this experiment were available Cd was added to soil,C.rotundifolia tolerated Cd concentra-tions below 2.0 mg/kg.C.rotundifolia has potential as a remediation plant to restore soil contaminated with Cd by mining operations in China’s south red soil region.