Effect of imidazolium's ionic liquids with different anions and alkyl chain length on phytotoxicity and biochemical analysis of maize seedling

The structural moieties of ionic liquids (IL), as well as water miscibility nature, render it toxic in the various biological system. The ecotoxicity of animals and microbes are well established for ionic liquids. Albeit, the phytotoxicity of ILs have not been explored exclusively. Therefore, the effect of three imidazolium-based ILs, namely, 1-butyl-3-methylimidazolium chloride ([Bmim]Cl), 1-octyl-3-methylimidazolium chloride ([Omim]Cl), and 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim]BF₄) on performance and biochemical constituents of maize seedling were studied. ILs in different concentrations ranging from 50 mg/L to 350 mg/L were applied to maize seeds continuously for 7 days under in vitro condition. The experimental results showed that ILs in high concentrations (250 and 350 mg/L) harm seed germination and seedling growth of maize, following the order: [Bmim]BF₄ > [Omim]Cl > [Bmim]Cl. ILs treatment caused a reduction in seed germination, weight of root and shoot, leaf area, relative water content, photosynthetic pigments production. The antioxidant activity of maize seedling was decreased when the concentration of ILs was increased, thus in ILs stressed condition, the free radical could not be effectively scavenged. However, an increase in the phenolic content was observed when ILs concentration increased from 50 mg/L to 350 mg/L. It has been observed that increasing alkyl chain length attached to imidazolium cation of ILs from butyl to octyl harm the performance of maize seedling. Moreover, IL having BF₄ anion is more toxic than ILs having Cl anion on maize growth seedling.