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

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.

Long‐term effects of copper rich swine manure application on continuous corn production

“…Applications of the high levels of Cu as either Cu rich manure or CUSO4 increased the DTPA extractable Cu in the three soils ( ship may reflect Cu uptake by roots with a low amount of Cu translocation from roots to shoots (1,11,12).…”

Plants can utilize iron form Fe‐N,N'‐di‐(2‐hydroxybenzoyl)‐ethylenediamine‐N,N'‐diacetic acid, a ferric chelate with 106greater formation constant than Fe‐EDDHA.

“…However, Romheld (1987) found that intact Fe-mugineic acid was accumulated by barley. By implication, Zn-and Cu-mugineic acid are also absorbed, and mugineic acid competition with DTPA for Zn or Cu was probably the characteristic being measured by Halvorson and Lindsay (1977) and Dragun et al (1976).…”

“…This should allow an estimation of the pCu 2+ , pMn 2+ , pZn 2 *, etc., at which soybeans can no longer remove these elements from nutrient solutions. Halvorson and Lindsay (1977) estimated the minimum pZn 2+ which allowed corn to obtain Zn was 10.6, and Dragun et al (1976) estimated the Tn-irnmim pCu 2+ from which corn could obtain adequate Cu was 13. It is now clear these papers probably relate only to Strategy-2 species where the competition is between the synthetic chelator and phytosiderophores such as mugineic acid.…”

Copper availability in two soils amended with eleven annual applications of copper‐enriched hog manure

“…An increase in phytotoxic response of corn (i.e. depression of root and shoot growth) corresponding to an increase in Cu content of plants, was observed by Dragun et al (16), only when plants were grown in Cu solutions, which were in equilibrium with soil solids, with concentrations greater than 1.26 mmol m" 3 .…”

“…Stunting of com plant growth upon exposure to Cu has been observed previously. Laboratory studies conducted by Dragun et al (16) revealed that corn plants grown in 10 mmol m~3 CuS0 4 solutions, in equilibrium with soil solids, resulted in a substantial decrease in height for plants after 4 wk compared to corn plants grown in solutions with Cu concentrations less than 10 mmol m~3. A far less dramatic decrease in plant height was observed for corn grown in 2.5 mmol m~3 Cu solution.…”