Foliar catechol oxidase activity as a measure of copper nutrition of tomato plants

Abstract

Abstract:The diagnostic value of catechol oxidase assays as indices of copper nutritional status was investigated in tomato plants (Lycopersicon esculentum Mill) receiving graded copper treatment in sand culture. Foliar copper concentrations ranged from 079 to 5-16 pg g-' dry matter under various copper treatments but these results were misleading because copper-inadequate plants concentrated the element in older leaves. A colorimetric assay based on catechol oxidase-catalysed formation of measurable quinones in young tomato leaves discriminated sufficiently between the various copper treatments. The rates of invitro induction of this enzyme amounted to an expression of the plant growth response to copper supply and thus was indicative of the copper requirement of the plant. A paper strip-based modification of the enzyme assay simplified it further for diagnostic use in field situations.