Effects Of Simulated Acid Rain And Cd Combined Stress On Maize Seedlings

Soil acidification and heavy metal Cd pollution are the most important soil environmental problems,both of those lead to further deterioration of the environment.Based on the maize as the research object,analysis of the simulated acid rain single stress,acid rain and Cd combined stress effects on maize seedlings.These studies are very important to pollution control,food safety and so on.1.Compared with their own controls,with the decreasing the p H value of acid rain,both single and combined stress led to the decrease of seed germination rate.While plant height,root length and plant fresh weight showed a tendency to rise after fall.Single and combined stress sensitive pH value was equal to 3 and 4,respectively.2.With the decreasing the pH value of acid rain,the activity of SOD and POD in single and combined stress showed a tendency to rise after fall,but the sensitive point is different,the former pH value was equal to 3,the latter was 4,this change has the same effect on growth.While the activity of CAT and GST,single stress continued to rise,combined stress showed a tendency to rise after fall,pH value is equal to 3 for sensitive point3.Chlorophyll changes showed that,with the increase of acid rain intensity,single and combined stress,chlorophyll content and chlorophyll fluorescence intensity showed a tendency to rise after fall.Chlorophyll content and chlorophyll fluorescence change are used to evaluate the effect of stress on plant photosynthesis,and these results are similar to the results of growth change,SOD and POD enzyme activity change.4.Using GC-MS technology combining with AMDIS software,49 kinds of metabolites were identified for single and combined stress on maize seedlings,including 10 amino acids,19 organic acids,10 carbohydrates and10 other substances.(1)The results of multivariate analysis of variance showed that thecontents of 49 kinds of metabolites were significantly changed by combined stress(P<0.05),suggesting that there was interaction effect between acid rain and Cd on metabolites.(2)The results of PCA analysis diagram showed that the different treatments all can be clearly distinguish,the same treatment of four repetitive scatters was relatively concentrated and better reproducibility.(3)Compared with blank control and the pH value of acid rain stress,the metabolic change rate analysis showed that amino acid,sugar,resistant substance content significantly increased(P<0.05),organic acid content was relatively stable.(4)According to the change of different processing metabolite rates map metabolic pathway plots.Metabolic pathways analysi can be concluded,both single and combined stress cause photosynthesis to be affected.Single stress tricarboxylic acid cycle stabilized,while combined stress tricarboxylic acid cycle blocked.5.The statistical test results showed that,compared with the control,5mg/kg Cd stress had no significant effect on seed germination,seedling growth,enzyme activity,chlorophyll content and chlorophyll fluorescence,while there was there was a significant difference in metabolic content and metabolic pathway(P<0.05).The results suggest that the effect of metabolites on maize seedling is more sensitive than physiological and photosynthetic changes.In summary,the sensitivity of single and combined stress to maize seedlings for pH value was equal to 3~4.There was interaction effect between acid rain and Cd on the metabolites.Its mechanism of action is mainly through the inhibition of photosynthesis and hinder the tricarboxylic acid cycle.Different treatments change in metabolites will continue to affect the late growth of maize,plant development,the quality of maize and so on.The research provides a meaningful basis for acid rain and heavy metalscombined stress on the effects of crops,recover soil pollution and so on.