Effects Of Three Alkylimidazole Ionic Liquids On The Growth And Development Of Brassica Napus Seedlings

Ionic liquid is a kind of salt with melting point below 100?,which composed of organic cation and inorganic or organic anion.Ionic liquids have been considered as"green solvents"due to their unique physical and chemical properties,and have been widely used in many fields.However,ionic liquids have potential ecological risks due to they are difficult to degrade.In recent years,the environmental toxicity risk assessment of ionic liquids has attracted extensive attention.A large number of studies have reported that the toxic effects and potential toxic mechanisms of ionic liquids on organisms.Recently,one of the hot topics is the toxic effects and mechanism of ionic liquids on crops.In this thesis,the effects of three alkyl imidazole tetrafluoroborate ionic liquids?[C_nMIM][BF₄],n=6?8?10?on the growth and development of Brassica napus seedlings were studied.The main contents and results were as follows:?1?The effects of three alkyl imidazole tetrafluoroborate ionic liquids on the growth of B.napus seedlings were investigated.The growth morphological changes of B.napus seedlings at different concentrations of ionic liquids by the growth inhibition experiments.The results showed that the growth of roots and shoots of B.napus seedlings were inhibited by three ionic liquids.Under the lowest treatment concentration(5?mol/L[C6MIM][BF4],0.5?mol/L[C₈MIM][BF₄]and 0.05?mol/L[C₁₀MIM][BF₄]),the root length and shoot length were longer than that of control group.With the increase of ionic liquid concentration,the growth of roots and shoots were inhibited.The EC_50,5d of roots length were lower than the EC_50,5d of shoot length in the three ionic liquids,which indicating that the toxicity effects of the three ionic liquids on roots were greater than on shoots.With the increase of the number of carbon atoms in the side chain of imidazole cation alkyl group,the EC_50,5d of root length and shoot length decreased gradually,which indicating that the order of toxicity of the three ionic liquids to B.napus seedlings was[C₆MIM][BF₄]<[C₈MIM][BF₄]<[C₁₀MIM][BF₄].?2?The physiological effects of three alkyl imidazolium tetrafluoroborate ionic liquids on roots and leaves of B.napus seedlings were investigated.Under the treatment of three ionic liquids,it can be found that:?a?with the increase of treatment concentration the of the ionic liquids,the contents of chlorophyll a,chlorophyll b and total chlorophyll of B.napus seedlings were raised first and then decreased,while the carotenoid content decreased gradually;?b?there was a high positive correlation between chlorophyll content and the growth of roots and shoots of B.napus seedlings;?c?with the increase of treatment concentrationthe of the ionic liquids,the malondialdehyde?MDA?content in roots and leaves of seedlings increased gradually,while the activity of superoxide dismutase?SOD?in roots decreased gradually;?d?the activity of catalase?CAT?and peroxidase?POD?of roots and the activity of SOD,CAT and POD of leaves were promotion at low concentration and were inhibition at high concentration.The change of MDA content indicated that there is peroxidation damage effect on membrane lipid of B.napus seedlings caused by ionic liquids.The change of antioxidant enzyme activity reflected the self-regulation of B.napus seedlings against ionic liquids stress.The results give evidence that ionic liquids caused oxidative damage to B.napus seedlings,which can be inferred that oxidative damage is one of the main toxic mechanisms of ionic liquids to B.napus seedlings.?3?Effects of alkyl imidazole tetrafluoroborate ionic liquids on root physiology of B.napus seedlings were investigated.With the increase of the concentration of three ionic liquids,the root activity of B.napus seedlings decreased gradually,while the root membrane permeability of B.napus seedlings increased gradually.It can be concluded that the three ionic liquids has cytotoxicity to root cells of B.napus seedlings.Under low concentration of three ionic liquids treatments,the cell structure of roots of B.napus seedlings were irreversibly damaged,and the degree of damage increased with increasing concentration.In addition,the chemical composition of roots of B.napus seedlings was characterized by means of FTIR.It can be found that the content of carbohydrates and proteins increased first and then decreased with the increase of the concentration of[C6MIM][BF4],but no change in the chemical composition.The results suggested that the change of organic matter content in roots of B.napus seedlings could protect the growth of shoots by reducing the imidazolium cations transport from the roots to the shoots.