Physiological parameters and metal-accumulating capacity of the biofuel plant Miscanthus × giganteus cultivated on oil-contaminated podzol soil treated with humic preparations

Background. Physiological characteristics of the biofuel plant Miscanthus × giganteus J. M. Greef, Deuter ex Hodk. & Renvoize are currently attracting much attention due to its phytoremediation potential. The aim of this work was to study the content of photosynthetic pigments in the leaves of M. giganteus, the accumulation of metals in the rhizosphere and aboveground organs, as well as the morphological parameters of plants cultivated on oil-contaminated soil and exposed to treatment with humic preparations. Materials and Methods. During field experiments, five experimental plots (PC and P1–P4) with an area of 1 m2 were laid out on podzol soil in the territory adjacent to the Starosambirske oil field. The PC plot was not subjected to any experimental treatment. The soil in plot P1 was planted with M. giganteus rhizomes; the soils in plots P2–P4 were contaminated with 10 L/m2 of crude oil and then planted with M. giganteus rhizomes. Before planting the rhizomes on plots P3 and P4, these were soaked in solutions of Fulvital® Plus Liquid and Humifield® Forte, respectively. During the growth period, the plants were sprayed twice with humic preparations. Shoot height and leaf width, a- and b-type chlorophyll (Chla and Chlb, respectively), total chlorophyll (Chla+b) and carotenoid concentrations were measured using standard methods. The content of metals (Ca, Cr, Cu, Fe, K, Mg, Mn, Ni, Pb, Zn) in soil and plant samples was assessed by X-ray fluorescence analysis using an Elvax Light SDD Analyzer. Results. The cultivation of M. giganteus on oil-contaminated soil did not affect shoot height or leaf width of plants, but it reduced the content of Chla, Chlb, Chla+b and carote­noids in plant leaves. Treatment of plants with humic preparations led to an increase in pigment concentrations in the leaves at different growth periods. Oil-contaminated soil planted with M. giganteus showed elevated levels of Cr and Ni. The cultivation of M. giganteus treated with Fulvital® Plus Liquid resulted in increased Ca, Mn and Ni contents in rhizosphere soil of an oil-contaminated plot. Growing M. giganteus on oil-contaminated soil resulted in significant decreases in Ca, Cr, Fe, K, Mg, Ni and Zn concentrations in plant stems. Treatment with humic preparations increased the content of the mentioned metals in the stems and the concentration of Mg and Ni in the leaves of plants from oil-contaminated soil compared to those in untreated plants. According to the bioaccumulation factor (BF) values, M. giganteus leaves have a high accumulation potential for Ni and Ca (BF>1), a medium accumulation potential for Mg, K and Cr (BF from 0.1 to 0.32) and a low accumulation potential for Fe and Zn (BF<0.1). The BF values of metals in leaves and stems decreased when plants were grown on oil-contaminated soil. Conclusions. Humic preparation treatment has a positive effect on the physiological parameters of M. giganteus grown on oil-contaminated podzol soil. The ability of M. giganteus to extract Ni from soil may mediate the plant’s phytoremediation potential. In this regard, the cultivation of M. giganteus in combination with its treatment with humic preparations will be promising on lands contaminated with oil and petroleum products.