Imidiazolium based ionic liquids: Effects of different anions and alkyl chains lengths on the barley seedlings

• Both anion and cation structure affected the toxicity of IL.
• ILs with more biocompatible anion did not lead to lower toxicity.
• Alternation in oxidative stress and antioxidant enzymes activities were found.
• Enhancement in antioxidative defense system leads to better barley performance.

We studied the effects of five imidiazolium based ionic liquids with different anions and length of alkyl chains linked to imidazolium ring on the early development of barley (Hordeum vulgare). The inhibitory effect depends on the ionic liquids concentration and chemical structure, whereby the most toxic one was [C10mim][Br], followed by [C7mim][Br], [C4mim][Br], [C4mim][CH3CO2] and [C4mim][BF4]. Both anion and cation structures affected the toxicity of ionic liquid indicating that selection of more biocompatible anions such as [CH3CO2] does not necessarily indicate lower toxicity. Alternation in the extent of oxidative stress and antioxidant enzymes activities were found in barley plants due to ionic liquid treatments. When seedlings were exposed to higher concentrations of ionic liquids, antioxidant system could not effectively remove reactive oxidative species, leading to lipid peroxidation and damage of the photosynthetic system. However, overall data indicated that the performance of barley seedling was improved when all measured enzymes involved in scavenging of reactive oxygen species (ROS) were increased with special emphasis on GPX activities. Since there are no studies about ionic liquid (IL) toxicity in plants, that simultaneously evaluates the antioxidative enzyme system in response to different ILs, this work is valuable for gaining knowledge about the protection mechanism of plants from oxidative stress caused by IL exposure.