VARIATIONS IN COPPER AND ZINC SUPPLY INFLUENCE GROWTH AND ACTIVITIES OF SOME ENZYMES IN MAIZE

Maize (Zea mays L.) cv. Ganga 2 was grown in refined sand at three lev els of copper: deficient (0.00065 mg L(-1)), adequate (0.065 mg L(-1)) , and excess (6.5 mg L(-1)), each at three levels, deficient (0.00065 mg L(-1)), adequate (0.065 mg L(-1)), and excess (6.5 mg L(-1)) of zin c. Excess Cu magnified the zinc deficiency effects in maize by lowerin g further the biomass, the concentration of leaf Zn, activities of car bonic anhydrase, aldolase, and ribonuclease and intensified the visibl e foliar symptoms of Zn deficiency. The effects of Cu deficiency, low dry weight, the concentration of leaf Cu and activities of cytochrome oxidase and polyphenol oxidase were enhanced by excess Zn. Synergism w as observed between combined deficiency of Cu and Zn and Cu or Zn defi ciency, because the depression in the parameters characteristic of Cu or Zn deficiency was more pronounced when both Cu and Zn were deficien t than when Cu or Zn was deficient. Antagonism was observed in some pa rameters between combined excess of Cu and Zn and Cu or Zn excess. Dry weight was decreased further when both Cu and Zn were in excess than when either Cu or Zn was in excess. After the infiltration of Cu and Z n together to the leaf discs from deficient Cu-deficient Zn treatment, the increase in the concentration of leaf Zn and the activities of al dolase, carbonic anhydrase, polyphenol oxidase, and cytochrome oxidase was more pronounced than after the infiltration of Cu or Zn singly. D iscontinuance of excess Zn supply from the excess Zn-deficient Cu trea tment increased the concentration of leaf Cu and activities of polyphe nol oxidase and cytochrome oxidase and lowered the concentration of Zn . Similarly the discontinuance of excess Cu supply from the leaf discs in the ''excess Cu-deficient Zn'' treatment increased the leaf Zn con centration and the activities of carbonic anhydrase and aldolase.