Biochemical Responses of Wheat Seedlings on the Introduction of Selected Chiral Ionic Liquids to the Soils.

In this study, new chiral ionic liquids (CILs) were obtained from the natural-origin material (1 R,2 S,5 R)-(-)-menthol. The physicochemical characteristics of the studied imidazolium salts were investigated. The obtained 3-ethyl-1-[(1 R,2 S,5 R)-(-)-menthoxy-methyl]imidazolium salts are nonvolatile, nonflammable, and stable in air, in contact with water, and in commonly used organic solvents. The influences of the obtained chiral salts on physiological and biochemical parameters were determined for wheat ( Triticum aestivum L.) seedlings. Both salts led to changes in plant metabolism, which resulted in decreased assimilation pigments, decreased fresh weight, and increased dry weight and proline in wheat seedlings. Moreover, the growth of the above-ground parts and roots was inhibited. Additionally, there was a drop in the potential and germination capacity of wheat seeds after using the highest concentrations of the ionic liquids. The salts caused oxidative stress in wheat seedlings, which was demonstrated by increased malondialdehyde content. In response, the plants engaged their defensive system against free oxygen radicals, which resulted in increased catalase and peroxidase activity and decreased H2O2 levels in the plants. There were no changes in the activity of superoxide dismutase. All of the changes observed in the levels of determined biomarkers of oxidative stress in the plants were linearly correlated with the increase in the concentrations of the chiral ionic liquids in the soil. The salt with hexafluorphosphate anion exhibited slightly higher toxicity toward wheat seedlings than the other salt. The CILs led to premature aging of plants, which was demonstrated by the increase in peroxidase activity and a decrease of chlorophyll in the seedlings. The experiment also showed good correlation between the increase in peroxidase activity and the decrease in chlorophyll level, which proves that the decrease in chlorophyll content resulted from not only the increase in CILs concentration in the soil but also the increased POD activity, which leads to the damage of chlorophyll particles.