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

Abstract

The positive impact on restoring soil functionality, decreasing toxic elements (TE) bioaccessibility, and enhancing soil physicochemical and biological parameters established a consensus on considering a Miscanthus x giganteus convenient species for phytomanaging wide TE contaminated areas. Nevertheless, information about the plant’s mode of reaction to elevated soil multi-TE concentrations is still scarce. For the sake of investigating the miscanthus response to stressful TE concentrations, an ex-situ pot experiment was initiated for 18 months, with three miscanthus cultivars referred to as B, U, and A planted in soils with gradient Cd, Pb, and Zn concentrations. A non-contaminated control soil was introduced as well, and plants were cultivated within. Results revealed that the long exposure to increasing soil TE concentrations caused the number of tillers per plant to decline and the TE concentrations in the leaves to boost progressively with the soil contamination. The photosynthetic pigments (chlorophyll a, b, and carotenoids) were negatively affected as well. However, the phenolic compounds, flavonoids, tannins, and anthocyanins, along with the antioxidant enzymatic activities of superoxide dismutase, ascorbate peroxidase, and glutathione reductase elevated progressively with the TE concentration and exposure duration. Conclusively, miscanthus plants demonstrated an intensified and synchronized antioxidative activity against the TE concentration.

Evaluation of Miscanthus × giganteus Tolerance to Trace Element Stress: Field Experiment with Soils Possessing Gradient Cd, Pb, and Zn Concentrations

“…These results corroborate what has been previously observed in other in situ and ex situ experiments on several contaminated plots with gradient T.E. concentration surrounding the Metaleurop site [ 8 , 15 , 19 ]. However, the leaf T.E.…”

“…This outcome contradicts the ones obtained by Zhang et al [ 25 ] who recorded a 1.82-fold increase in SOD activities in the leaves of miscanthus grown in Cd-spiked soils compared to the uncontaminated controls. The SOD and APX results also oppose the ones obtained in the pot experiment of Al Souki et al [ 15 , 19 ], who obtained a high increase in antioxidant enzymatic activities, especially in the most contaminated soils.…”

“…However, the leaf T.E. concentrations observed in the pot experiment of Al Souki et al [ 15 , 19 ], who used the same soils from the experimental fields as well as the same miscanthus cultivar, were over two times higher than the obtained results. The increase of T.E.…”

“…Generally, the secondary metabolites exhibited a similar approach to the antioxidant enzymes, with a few exceptions in flavonoids and tannins, which were more elevated in M700 plants. A different outcome was observed in the pot experiment of Al Souki et al [ 15 ], in which the secondary metabolites increased in a dose-dependent manner (recording more than two times the augmentation in M700 compared to MC) after two years of cultivation.…”

“…Briefly, the vast majority of the publications were based on ex situ experiments led under controlled conditions with a limited quantity of soils in which the plant roots were limited to certain pot areas, and hence T.E. uptake could be increased and cause the overstressing of the soil/plant system [ 15 ]. Moreover, several experiments were also established in unnatural contamination cases by artificially spiking the soils, which did not reflect the real T.E.…”