Changes in Salix viminalis L. cv. ‘Cannabina’ morphology and physiology in response to nickel ions – Hydroponic investigations

► Nickel was accumulated mainly in Salix viminalis L. roots and rod. ► Salix biomass parameters decreased significantly for subsequent Ni concentrations. ► Soluble carbohydrates content in Salix leaves increased in Ni-treated plants. ► Composition and content of low molecular weight organic acids in Salix rhizosphere changed in relation to Ni level. ► Phenolics and soluble carbohydrates probably regulate the exudation of low molecular weight organic acids by Salix roots. The aim of the study was to assess the ability of ‘basket willow’ to bioaccumulate nickel with simultaneous analysis of biomass parameters and biomarkers of plants physiological reaction to the metal. Cuttings of Salix viminalis L. cv. ‘Cannabina’ were cultivated in Knop's medium containing nickel at 0–3mM stabilized with quartz sand. Higher nickel contents were observed in Salix rods and roots (∼15), and lower for leaves and shoots (∼3mgkg−1DW) after 14days at 3mM Ni. The strongest inhibition was observed for root biomass, weaker for shoot, root and leaf elongation, and the weakest for the photosynthetic area (4, 24, 36, 55 and 70% of control, respectively). Soluble carbohydrates in leaves reached 340% of control at 3.0mM Ni. Phenolics content increased four-fold at 3mM Ni versus control, while salicylic acid content at 2.5mM Ni was nearly 68 times higher than for Ni-untreated plants. The exudation of low molecular weight organic acids increased from ∼40 to 130μMkg−1DW at 3mM. The investigated cultivar exhibits sufficient resistance to nickel and can be cultivated at heavily contaminated sites. Nevertheless, strong inhibition of plant growth was observed resulting probably from Ni-induced disturbances in nutrient uptake accompanied by oxidative stress.