Regulatory Effects Of Mancozeb And Propineb On Cadmium Accumulation In Wheat Seedlings

Manganese（Mn）and zinc（Zn）are essential micronutrients for plants,and they often exhibit an antagonistic effect with cadmium（Cd）elements in the plant body.Therefore,in the practice of safe utilization of Cd-polluted farmland,the application of Mn and Zn containing chemical agents from exogenous sources can effectively prevent the absorption and accumulation of Cd by crops,thereby achieving the goal of ensuring the quality and safety of agricultural products.Mancozeb and propineb are commonly used broad-spectrum and efficient fungicides that are rich in Mn and Zn.In this study,a hydroponic experiment was conducted to study the effects of applying mancozeb and propineb on the physiological and biochemical characteristics,Cd uptake and accumulation,and metabolic mechanism of wheat seedlings.The aim was to provide a theoretical basis and reference for safe utilization of contaminated farmland.The main results of this study are as follows:1.Propineb can significantly increase the fresh weight and root length of wheat seedlings,with maximum increases of 23.3%and 19.4%,respectively.Mancozeb reduced the fresh weight and root length of wheat seedlings.Under Cd stress,spraying mancozeb and propineb significantly increased the photosynthetic rate of wheat seedlings,with maximum increases of 165.1%and 114.7%,respectively,compared to the control.Spraying mancozeb reduced the CAT and SOD activity of wheat seedling leaves,with maximum decreases of 31.5%and 51.7%,respectively,compared to the control,while the H₂O₂content and superoxide anion scavenging capacity increased,with maximum increases of 68.5%and12.0%,respectively.However,when the Cd concentration was only 0.1 mg/L,the MDA content in wheat seedling leaves decreased by 4.6%.After spraying propineb,compared with the control,the CAT content in wheat seedling leaves decreased,with a maximum decrease of 32.9%;the H₂O₂ content and SOD activity increased with increasing concentrations of propineb,with maximum increases of 84.2%and24.7%,respectively;the MDA content in leaf blades showed a trend of first decreasing and then increasing,and the POD content showed a trend of first decreasing and then increasing,with a maximum increase of56.8%.The ability of wheat seedlings to scavenge superoxide anions increased,with a maximum increase of 7.3%compared to the control.2.Both mancozeb and propineb treatments can significantly reduce the content of Cd in wheat seedlings,and propineb has a better effect than mancozeb,with maximum reduction rates of 82.0%and45.0%,respectively,compared to the control.The subcellular Cd content in wheat seedlings was soluble components>cell wall>organelles.With increasing addition of mancozeb and propineb,the cell wall Cd content also increased,with maximum increases of 38.5%and 21.0%,respectively,while the Cd content in soluble components was inhibited,with maximum reductions of 35.7%and 20.0%,respectively.The Cd forms also changed significantly.Under the treatment of mancozeb,the percentage of Na Cl-extractable form(F_{Na Cl}),ethanol-extractable form（F_E）,and deionized water-extractable form（F_W）decreased,with maximum reductions of 10%,9.4%,and 12.2%,respectively,while the acetate-extractable form(F_HAc)and hydrochloric acid-extractable form(F_HCl)increased,with maximum increases of 16.6%and 5.9%,respectively.After spraying propineb,when the Cd concentration reached 0.1 and 0.5mg/L,the proportion of F_{Na Cl} increased first and then decreased,F_E and F_W proportions decreased,with maximum reductions of 17.2%and 7.9%,respectively,while F_HAc and F_HCl proportions increased,with maximum increases of 3.6%and 5.3%,respectively.3.Under no Cd stress,there were as many as 382 different metabolites in wheat seedling leaves,but the number of metabolites decreased to 185,201,and 210 under Cd concentrations of 0.1,0.5,and 1 mg/L,respectively.There were 11 common metabolites among the four treatments.The number of metabolites in wheat seedling leaves under propineb treatment varied greatly.There were 273 metabolites in wheat seedling leaves under the propineb treatment without adding Cd,and the number of metabolites increased first and then decreased with increasing Cd concentration,reaching 249,380,and 106,respectively.There were 8 common metabolites among the different treatments.Under different Cd concentrations,adding mancozeb and propineb led to 126 common metabolites in wheat seedling leaves.Mancozeb mainly responded to Cd stress by affecting amino acids,amines,and neurotransmitters,while propineb mainly affected compounds such as amino acids,neurotransmitters,and monosaccharides in response to Cd stress.Mancozeb treatment had unique compounds such as vitamin cofactors,carboxylic acids,and aminoglycosides,while propineb treatment had unique compounds such as peptides,fatty acids,and monosaccharides.