Effect of cadmium at concentrations of 1 and 10 μM on biomass increment, mineral nutrient elements (potassium, calcium, and magnesium) accumulation, and oxalic acid pools in organs of Amaranthus cruentus L. plants growing under water culture conditions was investigated. It was established that cadmium in the tested concentrations did not exert any pronounced damage effect on amaranth plants, which was in part shown to be associated with its predominant accumulation in roots and minimization of its transfer into young leaves. It was demonstrated that, in sublethal concentrations, this metal exerted growth response in the above ground amaranth organs expressed in stimulation of young leaves' growth, while simultaneously inhibiting growth processes in mature leaves. The results obtained are discussed in the context of determination of plant growth response to the effect of cadmium by certain metabolic changes whose functional manifestations consisted in carbon metabolism intensification and increase in water-insoluble oxalate content in amaranth leaves. Simultaneous observed increase in Ca²⁺ and Mg²⁺ levels in young and mature amaranth leaves is considered as additional evidence in favor of accelerating leaves' ontogenesis pace under the effect of sublethal doses of cadmium.