Differences Of Cadmium Accumulation And Transport In Different Maize Varieties And Its Mechanism

At the present stage,industry and agriculture are developing rapidly,but the related problems of heavy metal pollution in soil urgently need to be solved.Among them,cadmium(Cd)pollution is the most prominent problem.Heavy metals in farmland soil is difficult to degrade.Physical repair methods cost long time and money.Chemical repair methods are also easy to cause changes in soil physical and chemical properties.The cycle of hyperaccumulator is verylong.Low-accumulation crop varieties of phytoremediation can maintain the accumulation of heavy metals at a low level,so it is very important to select low accumulation crop varieties for planting in medium and low pollution soil.In this study,the difference of Cd accumulation of40 maize varieties was analyzed by pot experiment using polluted soil collected in sewage irrigation area.The paper culture experiment was used to carry out seed germination and elongation experiment,and the maize seedlings were cultured for 21 days in the soil supplemented with 2 and 20 mg / kg Cd to study the antioxidant enzyme system,photosynthetic characteristics and the response of rhizosphere soil enzymes to Cd stress.The main conclusions are as follows:(1)Different varieties of maize had different ability of absorbing and accumulating Cd,and the transper coefficient was negatively correlated with the Cd content of root system.The Cd content in roots of low Cd accumulation varieties was higher than that in aboveground parts.The varieties with high Cd accumulation were on the contrary.(2)The root weight and bud weight of the three varieties showed toxic excitatory effect under low Cd concentration stress,but inhibited at high Cd concentration,which showed an increasing trend with the increase of Cd concentration.In the aspect of mechanism research,there were significant differences in vigor index,root fresh weight,root dry weight,bud fresh weight and bud dry weight with different varieties.Among them,bud weight and vigor index showed the most significant changes to Cd stress,and also showed the difference among varieties better.High and low accumulation varieties can show better differences in rhizome elongation.(3)Under Cd stress,the seedlings of three maize varieties were all exposed to oxidative stress,SOD、POD、 CAT activity and MDA content also changed to different degrees.The seedlings of low accumulation variety Jia He 301 were seriously damaged by Cd stress.(4)Photosynthetic characteristics of cultivars with high and low Cd accumulation,that is to say,the response mechanism of chlorophyll content under Cd stress is different.Cd stress had no significant effect on the contents of chlorophyll a,chlorophyll b and total chlorophyll in leaves of low accumulation varieties Jing Kenuo2000 and Jia He 301.However,in leaves of Shen Hai 509,the contents of chlorophyll a,chlorophyll b and total chlorophyll were promoted by high concentration.Key words: farmland soil pollution,Cd,variety differences,low accumulation,mechanism study(5)20 mg/kg Cd promoted catalase activity in rhizosphere soil of Jiahe 301,but inhibited this index of Shenhai 509,when the concentration of CD was 2-20 mg / kg,the invertase activity in rhizosphere soil of jingkenuo 2000 was also significantly inhibited.However,the activities of urease and urease in the rhizosphere soil of Jiahe301 did not decrease,and even increased in some parts.