Effects Of Functionalized Imidazolium Based Ionic Liquids On Seed Germinaton And Seedlings Growth Of Maize

Organic solvents are harmful to ecological environment and human health.In recent years,people have been looking for environmentally-friendly alternatives,the ionic liquids enter the sight of people as an emerging"green solvent".The ionic liquids are widely used in different fields such as extraction,separation,catalysis and organic synthesis because the ionic liquids have many unique physicochemical properties.It is inevitable that the ionic liquids flow into the environment because of its usage.More and more studies have shown that the ionic liquids have varying degrees of toxicity to aquatic and terrestrial organisms.Therefore,it is necessary to evaluate the possible risks of the ionic liquids to environment and agro-ecological before their application.In present study,six kinds of functionalizded imidazolium based ionic liquids have been used to study the toxic effects of ionic liquids on maize by analyzed the germination rate of seed germination,the vigor index,the length of roots and shoots,the weight of roots and shoots,seedling growth indicators,the activities of antioxidant enzymes,malondialdehyde content,chlorophyll content and chlorophyll fluorescence parameters,which explored the effects of six kinds of imidazolium based ionic liquids with different substituent on maize seed germination,seedling growth and physiological mechanism,which provided a basis for evaluating the effects of ionic liquids on the ecological environment.The main results are listed as follows:1.In general,Low concentrations(1-10 mg/L,except[BzMIm]Cl)of the ionic liquids promoted the growth of plants in varying degrees.High concentrations of the ionic liquids inhibit the growth of plant.2.In the concentration range(1-1000mg/L),the six imidazolium based ionic liquids had no significant effect on the germination rate of maize seeds,and the effect on the vigor index was significant.The order is listed as below,[BzMIm]Cl>[AMIm]Cl>[EMIm]Cl>[CPMIm]Cl≈[HOOCEMIm]Cl>[AOEMIm]Cl.The six imidazolium based ionic liquids with different functional groups have different effects on the growth of maize seedlings.For the stem length of maize seedlings,the order of toxicity is listed as below,[BzMIm]Cl>[AMIm]Cl>[EMIm]Cl>[CPMIm]Cl>[AOEMIm]Cl>[HOOCEMIm]Cl;For root length of maize seedling,the order of toxicity is listed as below,[BzMIm]Cl>[AMIm]Cl>[HOOCEMIm]Cl>[EMIm]Cl>[CPMIm]Cl>[AOEMIm]Cl.3.Maize seedlings under treatment of six kinds of imidazolium based ionic liquids,the activities of antioxidant enzymes had changed.For antioxidant enzymes in stems,except the activities of SOD and APX under treatment of[HOOCEMIm]Cl,low concentrations of imidazolium based ionic liquids did not result significant variation on the activites of antioxidant enzymes.As the concentration of imidazolium based ionic liquids increased,the activites of antioxidant enzymes continued to increase.For antioxidant enzymes in roots,except the activites of CAT,APX under treatment of[AOEMIm]Cl,there was no significant change in the activities of antioxidant enzyme after treatment with low concentrations of ionic liquids compared with the control groups.As the concentration of imidazolium based ionic liquids increased,the activites of antioxidant enzymes continued to increase.The activities of POD had no significant variation under treatment of[AOEMIm]Cl,but at high concentrations,the other five ionic liquids induced a decrease of the activities of POD.4.MDA is a by-product of membrane lipid peroxidation,and the accumulation of MDA is often used as an important indicator to reflect the degree of stress in plants.In this study,the treatment of six ionic liquids caused an increase in MDA content in roots and stems of maize seedlings,indicating that the ionic liquids treatment caused peroxidation of maize plasma membrane and damage to roots and stems of maize.5.Chlorophyll plays an important role in plant photosynthesis.Six imidazolium based ionic liquids treatment significantly reduce the chlorophyll content of maize seedling leaves at high concentrations,as the same time,the chlorophyll fluorescence parameters F_V/F_M and F_V/F_O values were significantly reduced,indicating that the photosynthetic pigment content decreased and the photosystem function was impaired under ionic liquid s treatment.The trend of influence is consistent with the stem length.6.Maize seedlings under treatment of[AMIm]Cl were analized by RNA-Seq,a total of4024 differentially expressed genes were detected.The results of metabolic pathway analysis showed that,in the photosynthesis pathway,37 of the 42 differential genes were down-regulated under the treatment of[AMIm]Cl.And in the porphyrin and chlorophyll metabolic pathways,12 of the 15 differentially expressed genes were down-regulated.The above gene expression changes may be related to plant growth restriction and leaf yellowing under[AMIm]Cl treatment.