Physiological and molecular responses of flax (Linum usitatissimum L.) cultivars under a multicontaminated technosol amended with biochar

Soil pollution is a worldwide issue and has a strong impact on ecosystems. Metal(loid)s have toxic effects on plants and affect various plant life traits. That is why metal(loid) polluted soils need to be remediated. As a remediation solution, phytoremediation, which uses plants to reduce the toxicity and risk of polluted soils, has been proposed. Moreover, flax (Linum usitatissimum L.) has been suggested as a potential phytoremediation plant, due to its antioxidant systems, which can lower the production of reactive oxygen species and can also chelate metal(loid)s. However, the high metal(loid) toxicity associated with the low fertility of the polluted soils render vegetation difficult to establish. Therefore, amendments, such as biochar, need to be applied to improve soil conditions and immobilize metal(loid)s. Here, we analyzed the growth parameters and oxidative stress biomarkers (ROS production, membrane lipid peroxidation, protein carbonylation and 8-oxoGuanine formation) of five different flax cultivars when grown on a real contaminated soil condition, and in the presence of a biochar amendment. Significant correlations were observed between plant growth, tolerance to oxidative stress, and reprogramming of phytochemical accumulation. A clear genotype-dependent response to metal(loid) stress was observed. It was demonstrated that some phenylpropanoids such as benzoic acid, caffeic acid, lariciresinol, and kaempferol played a key role in the tolerance to the metal(loid)-induced oxidative stress. According to these results, it appeared that some flax genotypes, i.e., Angora and Baikal, could be well adapted for the phytoremediation of metal(loid) polluted soils as a consequence of their adaptation to oxidative stress.