Effects Of Atrazine And Cadmium Combined Stress On The Ecotoxicity Of Maize Seedlings

Atrazine(AT)is one of the commonly used herbicides in farmland in China.Recent years,heavy metal pollution incidents have occurred frequently in farmland.The combined pollution of soil herbicides and heavy metals has caused widespread public concern.Therefore,this paper studies the ecotoxicity effects of AT and Cadmium(Cd)compound stress on maize seedlings.A pot experiment was used to set different concentrations of single AT treatment and combined treatment with AT and Cd on the soil.Using chlorophyll fluorimeter,GC-MS metabolomics technology,etc,comprehensive analysis of maize seedling growth,antioxidant system,photosynthesis,metabolites and metabolic pathways were carried out.The main conclusions are as follows:1.Under the two stresses,the root length,root weight,plant height and plant weight of maize seedlings decreased continuously.The MDA content under single stress gradually increased;when AT concentrations were 12 and24 mg/kg,the combined stress significantly increased the MDA content,compared with asingle stress.Both stresses increased the activities of SOD,CAT and POD at 1.5 mg/kg,then gradually decreased.The interaction analysis results of AT and Cd showed the maize growth and three antioxidant enzymes showed antagonistic effects at AT 1.5 and 3 mg/kg;and synergistic effects at 6-24 mg/kg;it had antagonistic effects on MDA.2.The total chlorophyll content of both stresses increased slightly when AT was 1.5 and 3 mg/kg,and decreased significantly when AT was 6-24mg/kg.At high concentrations,the chlorophyll content of compound stress was significantly lower than single stress.The interaction type of AT and Cd on chlorophyll is antagonistic,when AT was 1.5 and 3 mg/kg;and 6-24mg/kg was synergistic.The chlorophyll fluorescence kinetic curves were consistent with the effect of chlorophyll.The results of chlorophyll fluorescence parameters indicated that with the increase of AT concentration,both stresses significantly inhibited the electron transfer in the photosynthetic apparatus at high concentrations,affected the absorption of light energy by the reaction center,caused damage to the receptor side,and accelerated energy dissipation,and triggered the activation of the protection mechanism of plant photosynthetic apparatus.3.Based on GC-MS,all the treatments were screened 49 metabolites of corn seedlings.(1)The results of PCA analysis showed that the different treatments were clearly distinguished,and the metabolites are significantly different.(2)The screening results of differential metabolites analyzed by OPLS-DA showed that the single stress increased with AT concentration,24,27,25,30 and 33 differential metabolites were screened separately,compared with the blank control;Compared with single stress at the same concentration,when the AT concentration of compound stress is 0,1.5,3,6,12,24 mg/kg,are screened different metabolites14,13,14,15 17 and 24.The comprehensive analysis results suggested that different stresses lead to changes between different treatments and different concentration ranges,up-regulation and down-regulation of different metabolites in different treatments and concentration ranges,which affect the disruption of different metabolic pathways.(3)The analysis of metabolic pathways through the KEGG platform showed that there were 16 metabolic pathways sorted out by the single and compound stress,among which 9 were common to both.There were 5 for the single stress and 2 for the compound stress.The results suggested that the two kinds of stresses mainly affect the metabolism of amino acids,carbohydrates and lipids.That is to say,the two kinds of stress through the up-regulation of sugars and amines and changes amino acid substances,then reconstructed the metabolism of starch and sucrose,galactose metabolism,glyoxylate and dicarboxylate metabolism,TCA cycle and glutathione metabolism.To reduce the toxic effects of the two stresses.In summary,both AT single stress and AT+Cd combined stress affected the growth,antioxidant systems,photosynthesis,metabolites and metabolic pathways.The effects of AT and Cd compound stress on each index are interactive.The high concentration of AT compound stress aggravated the oxidative damage,the inhibition of photosynthesis,and the influence on the changes of metabolites and metabolic pathways of maize seedlings.