MICRONUTRIENT DEFICIENCY CHANGES ACTIVITIES OF SUPEROXIDE-DISMUTASE AND ASCORBATE PEROXIDASE IN TOBACCO PLANTS

The effects of copper (Cu), zinc (Zn), and manganese (Mn) deficiencies on the activities of superoxide dismutase (SOD) and ascorbate peroxid ase (APx) were investigated in seedlings of Nicotiana tabacum cv. Xant hin. After germinating in sand for 7 days, plants were transplanted to solution culture with all nutrients or without Cu, Zn, or Mn. Plants grown without Mn developed visual deficiency symptoms 15 days after tr ansplanting (DAT), and those grown without Zn showed Zn deficiency sym ptoms 26 DAT. In contrast, plants grown without Cu showed only minor s ymptoms of Cu deficiency at 33 DAT. When harvested 41 DAT, -Mn plants suffered the largest, and -Cu the smallest reduction in shoot dry weig ht compared to plants supplied with all nutrients. Nutrient analysis i n leaf tissue showed a considerable decrease in concentration of nutri ents not supplied to plants. Total SOD, MnSOD+FeSOD, Cu/Zn SOD, and AP x activities declined drastically in -Mn and -Zn plants, while total S OD, MnSOD+FeSOD and APx activities in -Cu plants remained significantl y higher than those of control plants. It was concluded that micronutr ient deficiencies (Cu, Zn, and Mn) can alter the activities of antioxi dative enzymes in tobacco plants depending on the severity and the typ e of the deficiency stress.