The study examined the influence of copper salt at concentrations ranging from 50 to 250 mg dm^-3 on the physiological reaction of the Bjor and Jorr varieties of common osier. The content of assimilation pigments, the intensity of CO₂ assimilation, transpiration, stomatal conductance for CO₂ and water vapour, coefficients of the relative water content and water saturation deficit were determined. The intensity of CO₂ assimilation, transpiration and the assimilation pigment content in the tested common osier cultivars varied with relation to the copper salt dose in the medium. A decrease in the intensity of the tested physiological parameters was found together with an increase in the copper salt dose in the medium. CO₂ assimilation and transpiration of the Bjor and Jorr osier was significantly limited by the stomata. The addition of copper salts to the medium resulted in an increase in the water saturation deficit in leaves of the tested common osier varieties.