Physiological and biochemical responses of wheat (Triticum aestivum L.) seedlings to three imidazolium-based ionic liquids in soil

Abstract

Ionic liquids (ILs) are considered environmentally friendly solvents and are widely applied in various fields; however, some researchers have noted the toxicity of ILs to plants cultivated in nutrient solution. To evaluate the toxicities of ILs to wheat seedlings in soil, the natural growth environment of plants, a study was performed using three imidazolium-based ionic liquids with different anions: 1-octyl-3-methylimidazolium chloride ([C8mim]Cl), 1-octyl-3-methylimidazolium bromide ([C8mim]Br) and 1-octyl-3-methylimidazolium tetrafluoroborate ([C8mim]BF4). After 13 d of exposure to these three ILs at 0, 100, 200, 400, 600 and 800 mg kg−1 in brown soil, wheat seedlings were randomly sampled to evaluate growth (shoot length, root length, pigment content and proline content), lipid peroxidation, oxygen species (H2O2 and O2−) and activities of the detoxification enzyme glutathione-s-transferase and other antioxidant enzymes, including superoxide dismutase, catalase and peroxidase. The experimental results showed that all three ILs had inhibitory effects on the growth of wheat seedlings and induced the generation of reactive oxygen species, which indicated that the wheat seedlings suffered oxidative stress. Moreover, antioxidant enzyme activity was enhanced after exposure to [C8mim]Cl, [C8mim]Br and [C8mim]BF4, demonstrating that oxidative damage may be the primary underlying mechanism of IL toxicity in wheat.