砷对玉米生长、抗氧化系统及离子分布的影响

Effects of arsenic on maize growth,antioxidant system,and ion distribution

采用温室砂培试验,研究了不同浓度砷(As)处理对玉米郑单958幼苗生物量积累、光合色素含量、抗氧化系统、As及矿质离子吸收、分布的影响.结果表明:低浓度(<2mg·L-1)的As刺激了玉米幼苗的生长,植株株高、主根长和生物量积累均显著增加;高浓度(>4mg·L-1)As严重抑制了玉米幼苗生长.2mg·L-1As处理下,叶绿素a、叶绿素b和叶绿素a+b含量均达到峰值;随As处理浓度增加,叶绿素含量逐渐下降;电镜观察发现,10mg·L-1As处理下,叶片叶绿体结构遭到破坏,类囊体膜溶解.根系3种抗氧化酶(SOD、POD、CAT)活性均随As浓度增加而增大;叶片3种抗氧化酶活性在8mg·L-1出现峰值,且对As处理的敏感性表现为POD>CAT>SOD.MDA、可溶性糖和可溶性蛋白含量与As浓度呈正相关.高浓度的As明显抑制了P、K、Ca、Fe等元素的吸收.根系对As胁迫的反应比地上部更为敏感,因此根系生长发育指标更适合作为植物As毒害的指示指标.

A greenhouse sand culture experiment was conducted to study the effects of arsenic （ As） on the biomass accumulation,photosynthetic pigments,antioxidant system,and the absorption and distribution of As and mineral ions in maize Zhengdan 958. At lower concentrations （ 2 mg As·L -1） ,As stimulated the growth of maize seedlings,and increased the plant height,taproot length,and biomass accumulation significantly; at higher concentrations （ 4 mg As·L -1） ,As inhibited the seedlings growth severely. At 2 mg As·L -1,the chlorophyll a,b,and a ＋ b contents reached their peaks; but with increasing As concentration,the chlorophyll contents decreased gradually. At 10 mg As·L -1,the destruction of chloroplast structure and the dissolution of thylakoid membrane were observed by electron microscopy. With increasing As concentration,the activities of antioxidant enzymes SOD,POD,and CAT in root increased,and those in leaf reached the maximum at 8 mg As·L -1. The sensibility of the enzymes in leaf to As stress was in the order of POD CAT SOD. Correlation analysis showed that the contents of MDA,soluble sugar,and soluble protein were positively correlated with As concentration. High concentration As inhibited the absorption of P,K,Ca,Fe and other elements obviously. And comparing with shoot,root was more sensitive to As stress. The growth indices of root could be more available to be used as the indicators of plant arsenic toxicity.