壳聚糖对镉胁迫下玉米幼苗根系抗氧化酶活性和内源激素水平的影响

Effects of Exogenous Chitosan on Antioxidant Enzyme Activities and Endogenous Hormones in Maize Seedling Roots under Cadmium Stress

为探究壳聚糖对增强玉米幼苗抗镉胁迫能力的生理生化机制,以玉米(Zea mays L.)杂交种‘郑单958’为试验材料,采用室内Hoagland水培法,探讨外施100mg·L^(-1)壳聚糖对镉胁迫(80mg·L^(-1))不同时间(0h、24h、48h、72h和96h)下玉米幼苗根系抗氧化酶活性和内源激素水平的影响。结果显示:(1)镉胁迫显著抑制玉米幼苗根系生长,并诱导根系活性氧产生、抗氧化酶活性增加、内源激素的平衡受到破坏。(2)镉胁迫下,外施壳聚糖处理96h后根系干重提高16.1%,根系的O-·2产生速率和H2O2含量分别降低9.1%和19.2%,SOD、POD和CAT活性分别提高32.5%、20.4%和21.3%,IAA、ZR和GA含量分别增加34.4%、40.4%和42.5%,ABA含量减少19.1%,IAA/ABA、ZR/ABA和GA/ABA分别提升66.1%、73.5%和76.0%。研究表明,壳聚糖能够调控镉胁迫下玉米幼苗根系内源激素的含量及平衡,减轻胁迫对抗氧化酶系统的破坏,增强其清除活性氧的能力,从而降低镉胁迫对根系的毒害,提高玉米幼苗对镉胁迫的抵抗能力,为玉米抗逆栽培提供了理论及试验依据。

In order to investigate the physiological and biochemical mechanism of chitosan to improve the tolerance of maize seedlings to cadmium stress,we chose maize（Zea mays L.）cultivar‘Zhengdan 958＇as experimental material and cultivated via Hoagland hydroponics in plant growth chamber.Maize seedlings were treated with chitosan of 100mg·L^-1 under Cd^2＋ stress at different time points（0,24,48,72,96h）.The aim of this experiment was to examine the effects of chitosan on the antioxidant enzyme activities and endogenous hormone levels under cadmium stress.The results showed that：（1）under cadmium stress,the growth of maize seedling roots was inhibited,the generation of ROS was induced,the activities of antioxidant enzymes were increased,and the balance of endogenous hormones was destroyed.（2）Aftertreated with chitosan under cadmium stress for 96 h,the dry weight of root increased by 16.1%,the generation rate of superoxide radical（O2^-·）and the content of H2O2 in roots decreased by 9.1% and 19.2%,respectively.The activities of SOD,POD and CAT were increased by 32.5%,20.4%and 21.3%,respectively,IAA,ZR and GA were increased by 34.4%,40.4%and 42.5%,respectively,and ABA decreased by 19.1%.IAA/ABA,ZR/ABA and GA/ABA increased by 66.1%,73.5% and 76.0%,respectively.The results indicate that under cadmium stress,chitosan could regulate the content and balance of endogenous hormones in maize seedling roots,reduce the damage of antioxidant enzyme system and enhance the ability to scavenge ROS.Thus,chitosan alleviated the toxicity of cadmium stress to roots and improved the resistance of maize seedlings.The study provided the theoretical and experimental basis for the application of chitosan to the cultivation of maize under stress.