Response of Three Miscanthus × giganteus Cultivars to Toxic Elements Stress: Part 1, Plant Defence Mechanisms

Abstract

Miscanthus × giganteus demonstrated good phytostabilization potentials in toxic element (TE) contaminated soils. However, information about its tolerance to elevated concentrations is still scarce. Therefore, an ex-situ pot experiment was launched using three cultivars (termed B, U, and A) grown in soils with a gradient Cd, Pb and Zn concentrations. Control plants were also cultivated in non-contaminated soil. Results show that the number of tillers per plant, stem diameter as well as leaf photosynthetic pigments (chlorophyll a, b and carotenoids) were negatively impacted by soil contamination. On the other hand, phenolic compounds, flavonoids, tannins, and anthocyanins levels along with the antioxidant enzymatic activities of superoxide dismutase, ascorbate peroxidase and glutathione reductase increased in the plants grown on contaminated soils. Altogether, these data demonstrate that miscanthus is impacted by concentrations of toxic elements yet is able to tolerate high levels of soil contamination. These results may contribute to clarifying the miscanthus tolerance strategy against high contamination levels and its efficiency in phytoremediation.

Response of Three Miscanthus × giganteus Cultivars to Toxic Elements Stress: Part 2, Comparison between Two Growing Seasons

“…Table 1 represents the TE concentrations in the studied soils. As previously shown by Al Souki et al [ 20 , 24 ], the TE concentrations in MC were in agreement with the regional background values (0.42, 38, and 74 mg kg −1 , corresponding to Cd, Pb, and Zn, respectively). Whereas the other soils displayed pseudo total concentrations 20 to 50 times higher than the regional agricultural background values.…”

“…However, the experiments that evaluate TE impacts on miscanthus health are scarce and have never been undertaken for more than three months. In the previous work [ 24 ], after a full growing cycle on TE contaminated soils (T1), we demonstrated that miscanthus plants exhibited TE-induced stress (an increase in antioxidant enzymatic activities, a decrease in photosynthetic pigment content, and an enhancement of secondary metabolite accumulation). However, results also demonstrated that miscanthus plants were quite tolerant to TEs as no significant differences were observed between plants growing on different soils with an increasing gradient in TE concentrations.…”

“…Antioxidative enzymatic activity assays were evaluated spectrophotometrically according to Al Souki et al [ 24 ], using a plate reader (Thermo Scientific Multiskan™ GO, Illkirch-Graffenstaden, France). Briefly, five foliar discs (0.5 cm diameter) per plant sample were collected from frozen leaves by a manual punch.…”

“…Photosynthetic pigments, phenolic compounds, tannins, flavonoids, and anthocyanins were determined spectrophotometrically, according to Al Souki et al [ 24 ], by a plate reader (Thermo Scientific Multiskan™ GO). Briefly, two foliar discs (0.5 cm diameter) per plant sample were collected from frozen leaves using a manual punch and weighed.…”

“…Within this context, the current work is part of a larger study aimed at understanding the influence of Miscanthus × giganteus on soil parameters [ 4 , 20 ] and its tolerance to TEs during two growing seasons [ 24 ]. In this study, we investigated the response of Miscanthus × giganteus plants cultivated in pots filled with soils from the Metaleurop area with a gradient concentration of Cd, Pb, and Zn, after 18 months of cultivation (two growing periods).…”