Phytoremediation of heavy metal nanoparticles by plantain (Plantago) plants

Industrial activities that have gained acceleration and the unconscious use of natural resources in parallel with the rapidly growing world population directly facilitate the increase of environmental pollution. As a result of nano-industrial activities, nano-level particles such as ZnO (Zinc Oxide) can be released into the environment and accumulate in toxic quantities. This situation has become a global problem that seriously threatens nature and human health. Nanoparticular heavy metals show differences in their physical and chemical properties according to their bulk conditions. For this reason, the mechanisms of interactions with the environment need to be revealed through detailed research. Because of their cosmopolitan distribution and adaptation to changing ecological conditions, Plantago major L. and Plantago lanceolata L. species were chosen as model plants. Our experiments were carried out in sand cultures and plants were treated with 100 mg/L nanoparticular (P. S. <50 nm) and bulk ZnO for 15 days. ZnO toxicity and Zn accumulation in roots and in the above-ground plant organs were investigated. Effects of Zn on the uptake of Ca, K, Mg, Mn, Fe together with the developmental and phytotoxic differences in plants were evaluated and the phytoremediation potential of plants were discussed. There were no statistically significant differences between the control and application groups among the leaf size, shoot length, root and above-ground weights of plants and tolerance indices. At the same time, the parameters related to carotenoid production and PSII activities were not affected by the bulk and nanoparticular ZnO applications. On the other hand, some differences were found in the physiological parameters such as water content percentages, chlorophyll values, phenolic amounts in roots, ion leakage and cell membrane damage levels with root/shoot rates. It is determined that some photosynthetic parameters, especially NPQ, may be good indicators for the reactive values of nanoparticular and volumetric ZnO applications according to the levels of spatiotemporal heterogeneity found in visual expressions of PSII activities measured on leaves. As a result of the elemental analysis, it was determined that the bulk and nanoparticular Zn applications generally prevent the transfer of nutrients such as Ca, Mg, Fe and Mn to the above-ground organs, thus increasing the accumulation levels of these elements in the roots or inhibiting their transition from the culture media to the roots. However, the levels of K accumulation in the application groups show some differences compared to the control groups. Although Zn accumulation increased similarly in both species, the levels of bioconcentration were higher, especially in the roots. Considering the average Zn accumulations; P. major L. species was found to accumulate about 17.71% more Zn than P. lanceolata L. species. According to the results of the accumulation, translocation and bioconcentration factors, it can be concluded that both Plantago species were capable of being used in the phytostabilization of the areas contaminated with nanoparticular or bulk ZnO.