Copper and nickel co-treatment alters metal uptake and stress parameters of Salix purpurea × viminalis

Simultaneous treatment of Salix purpurea × viminalis with copper (Cu2+) and nickel (Ni2+) altered metal phytoextraction rates in favor of leaves. Still, metal translocation patters remained unaffected (roots ≈ rods >> leaves ≥ shoots), reaching ∼20 and 14.5 mg kg−1 dry weight in roots for Cu and Ni, respectively. Biometric parameters revealed overall growth inhibition correlated with Cu content in leaves, thus proving its negative effect on photosynthesis. Metal toxicity was strongly affirmed in the case of roots (∼90% loss of root biomass at 3 mM), rather than in the above-ground organs. Plant treatment accelerated the accumulation of soluble carbohydrates, phenolics including salicylic acid and glutathione in Salix leaves. However, significant differences in plant reactions to the applied metals were noted. Metal accumulation in leaves was correlated with soluble sugars and elevated glutathione, and also with total phenolics content, in the case of Cu and Ni, respectively. Glutathione synthesis was induced by both metals, and correlated with salicylic acid in leaves of Ni-treated plants.