Growth and Element Accumulation by two Single‐cross Corn Hybrids as Affected by Copper in Solution1

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Abstract
Increased use of land for “disposal” of industrial wastes and animal wastes such as poultry and swine manure from flocks and herds fed high levels of trace elements will require soil monitoring methods to maintain safe levels of these elements with respect to both crop production and the food chain. The objectives of this investigation were to: 1) measure Cu ion potentials, pCu, associated with minimum and maximum Cu ion activities for growth of corn (Zea mays L.) seedlings; 2) evaluate the influence of the chelator DTPA (diethylenetriaminepentaacetic acid) on plant uptake of Cu; and 3) relate pCu to uptake of Cu and other elements by single‐cross corn hybrids selected for genetic controlled accumulations of relatively high and low concentrations of leaf Cu.Two corn hybrids were grown in the greenhouse using solution cultures of varying pCu. Other essential elements were held constant in solution or supplied by frequent application to 100 g of soil supporting the plants above the solution. For the constantly aerated solutions, pCu, as calculated from formation constants of Cu‐DTPA complexes and pH and as measured with a Cu specific ion electrode, was biologically equivalent to those obtained for solutions devoid of DTPA. For both hybrids, root and top growth were reduced due to Cu toxicity when pCu was ≤ 5.78. A deficiency of Cu was associated with a pCu > 13. While Cu concentrations in plant tops increased with decreasing pCu for both hybrids, the hybrids were different as predicted from the performance of the parental inbred lines. At high levels of Cu (pCu of 5 to 7) hybrid differences and changes in plant concentrations of Cu with pCu in solutions indicated that plant composition could not be used to indicate toxic substrate levels of Cu.