The effect of copper (Cu), zinc (Zn) or manganese (Mn) deficiency on the growth and activity of superoxide dismutase (SOD) forms was investigated in seedlings of narrow-leafed lupins (Lupinus angustifolius L.). Plants grown without Zn developed Zn deficiency symptoms 24 d after sowing (DAS), and those grown without Mn showed Mn deficiency symptoms 31 DAS. However, plants grown without Cu did not show visible leaf symptoms. Shoot dry weight was decreased by Zn and Mn deficiency 24 DAS, and by Cu deficiency 31 DAS. Soluble protein concentration was reduced considerably by Zn deficiency 24 DAS, but was not affected by Cu deficiency until 31 DAS. In contrast, soluble protein concentration in Mn-deficient plants was higher than in control plants 31 DAS. Shoot concentration of micronutrients which were not supplied to plants decreased significantly, with a simultaneous increase in concentration of one or more of the other nutrients analysed. The activities of total SOD, MnSOD and Cu/ZnSOD on a fresh weight basis declined drastically in -Cu and -Zn plants 24 DAS. On the contrary, the activities of total SOD and Cu/ZnSOD on either a fresh weight or soluble protein basis increased markedly in -Mn plants 24 DAS, and MnSOD activity increased significantly in these plants 31 DAS. It was concluded that micronutrient deficiency (Cu, Zn or Mn) altered the activities of SOD forms depending on the kind and severity of the deficiency stress. Manipulation of the capacity of plants to tolerate oxidative stress may influence their capacity to tolerate micronutrient deficiency. (C) 1999 Annals of Botany Company.