| Ionic liquids, completely composed of ions and melting point below 100 ℃, are a kind of organic salts. Due to their unique physicochemical properties like stable characteristic,strong electrical conductivity, negligible vapor pressure and non-flammabling, ionic liquids which show good solubility for many inorganic salts and organic matter, are recognized as environment friendly alternatives to traditional volatile organic solvents in the new century.However, with the wide application in various fields, ionic liquids will inevitably be released to the environment, bringing potential risks to the environment and the organisms. The related study progress of the toxicity of ionic liquids to plants is far lagging behind the research of their physicochemical property and application development. And the basic data of the toxicity of ionic liquids on plants is lack. So studying the toxicity of ionic liquids to the plant is vitally significant.In this study, the ecological toxicity to the wheat of Jimai 22 of three kinds of imidazoles ionic liquids [C8mim]Cl, [C8mim]Br and [C8mim]BF4 was studied at concentrations of 0, 100, 200, 400, 600 and 800mg/kg in soil. At day 13 of cultivating, the following indicaters were measured: shoot length, root length, pigment, praline,malondialdehyde(MDA), hydrogen peroxide(H2O2), superoxide anion(O2-), superoxide dismutase(SOD), catalase(CAT) and peroxidase(POD). The main research results are as follows :(1)From the point of growth index, all the three kinds ionic liquids led to a decline in both shoot length and root length, inhibiting the growth of wheat seedlings. Influences on the wheat shoot length of all the three ionic liquids showed significant dose effect relationship. At concentration of 200 mg/kg, compared to the control group, the inhibition rate of shoot length of [C8mim]Cl, [C8mim]Br and [C8mim] BF4 was 21.6%, 25.6% and 25.7%, respectively; atconcentration of 800 mg/kg reaching 60.3%, 65.4% and 60.3% respectively. Meanwhile,the root length inhibition rates at concentration of 200 mg/kg were all over a half. The indicator of root length showed more sensitive to ionic liquids.On inhibition rates of wheat shoot length and root length, the toxicity characterized by three kinds of ionic liquids showed[C8mim]BF4>[C8mim]Br>[C8mim]Cl.(2) Chlorophyll content: All the three kinds of ionic liquids made a decline of chlorophyll contents of chlorophyll a, chlorophyll b and carotenoid in wheat leaves. It showed a significant dose effect relationship between chlorophyll contents and exposure concentrations from the concentration of 200mg/kg.(3) Proline content: With the rising of the exposure concentrations, proline contents in wheat leaves presented significant rising trend on the whole in all treatment groups. In[C8mim]Cl and [C8mim]Br groups, proline contents rised slowed from concentration of 400mg/kg; and [C8mim]BF4 group showed a continuous rise in prolin content.(4) Malondialdehyde(MDA) content: In [C8mim]Cl and [C8mim]Br groups, MDA content in wheat leaves did not change significantly under low concentrations,rising under high concentrations. Meanwhile, in [C8mim]BF4 group, the content of MDA showed an obvious rising trend.(5) Hydrogen peroxide(H2O2) and superoxide anion(O2-) content: Dyeing degree indicated the content level of H2O2 and O2 in wheat leaves. All the three ionic liquids induced a significant rise of the content of H2O2 and O2- in wheat leaves.(6) Antioxidant enzyme system: SOD, CAT and POD were selected as indicators. SOD activity showed significant rise only at high concentrations in both[C8mim]Cl and [C8mim]Br groups but it was always rising in [C8mim]BF4 group with the rising of concentrations. In all the three ionic liquids groups, CAT activity and POD activity showed significant rise compared to the control and represented a rise trend with the increasing concentrations. |
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