The effect of excess copper (Cu) on young spinach (Spinacia oleraced) as well as the role of iron (Fe) for amelioration of toxicity on growth and photosynthesis in Cu-treated plants was evaluated. Plants treated with 160 μM Cu showed symptoms of heavy metal toxicity, while addition of Fe (40 μM) ameliorates to a certain extent toxic effects of Cu, due to antagonistic action between Cu and Fe. Root length and biomass revealed a lower decrease under Cu+Fe than under Cu treatment. Copper accumulation in plant tissues increased, while Fe, sodium (Na), potassium (K), calcium (Ca), and magnesium (Mg) declined under Cu treatment. The significant increase in chlorophyll fluorescence (F o ) under 160 μM Cu, possibly reflects the more severe damages suffered at the membrane level with respect to Cu+Fe treatment. Copper decreased the efficiency of excitation energy capture by PSH reaction centers and negatively affected the effective antenna size of PSH. Changes in the rate 2089 OUZOUNIDOU ET AL. of carbon dioxide (CO 2 ) assimilation were associated with changes in both stomatal conductance (gs) and mesophyll capacity for photochemistry as well as with lower pigment content. Net CO 2 assimilation, transpiration rate, and stomatal conductance were reduced. These changes at PSII are characteristic of a saturation of photosynthetic metabolic activity. The results suggest a tight linkage between PSII activity and CO 2 fixation under Cu treatment. Amelioration of Cu toxicity was obvious under Fe application.