The effect of cadmium on some parameters of growth (root and shoot increment, leaf area), photosynthetic activity (content of photosynthetic pigments, quantum efficiency of the photosystem II, electron transport rate, photosynthetic rate) and the water regime (number and size of stomata, stomatal aperture width, transpiration intensity, and stomatal conductance) in barley plants was studied in relation to plant age. Cadmium at a concentration of 100 мM was found to inhibit root growth in 3-day-old plants, suppress their photosynthetic activity, and disturb the water regime, but no delays in the growth of above-ground parts are observed. In 9-day-old plants, stem growth in the presence of the metal is inhibited, and leaves are smaller, whereas photosynthetic processes and the water regime remain quite active. Neither is root growth inhibited in them. Conjectures have been made concerning potential causes of the age-related differences in the response of barley plants to cadmium.