Iron and Copper Enzymes in Leaf Lamina of Tobacco When Deficient in Micronutrients or Grown on Calcareous and Organic Soils

Abstract

Certain enzyme responses in plants were considered by Bailey and McHargue (1), Mac Vicar and Burris (6), and Quilan-Watson (7) as the effects of an element on a particular enzyme system. Enzymatic activity has been used by Brown and Hendricks (2) as indicative of the type deficiency produced in chlorosis susceptible plants grown on a naturally calcareous soil and a copper-deficient organic soil. Relative activities of ascorbic acid oxidase (copper enzyme?AAO), catalase and peroxidase (iron enzymes) were determined for wheat, corn, tobacco, three species of lupines, and two varieties of soybeans. The ascorbic acid oxidase activity was reduced in plants grown on the copper-deficient soil and a comparatively reduced catalase activity was observed in plants grown on the naturally calcareous soil. These data verified the assumption that if copper or iron, respectively, were the limiting factors in the plant's nutrition, the deficiencies would be revealed as diminished activities of one or more of the enzymes requiring a specific element to function properly. In recognition of the possibility that similar results might have been obtained through uncontrolled variations in other micronutrient elements, these experiments have been repeated, using tobacco, for the comparison of plants deficient in specific micronutrients. Comparisons of enzymatic activity patterns resulting from specific micronutrient deficiencies with those of plants grown on calcareous and organic soils were considered desirable. Coincidence in responses under the widely different environmental conditions of soil and water-culture would be strong additional evidence of the cause of the soil abnormalities. Moreover, since the calcium carbonate method for removal of micronutrient impurities also removes many of the unessential trace element impurities, the latter could also be minimized as contributory factors.