Zinc chelate inhibited uptake of copper and manganese, or is it chelating agent inhibition? — Differential zinc accumulation in primary leaves

Abstract

Zinc DTPA, but not ZnEDTA, inhibited Mn uptake by bush bean plants at high solution pH just as much as did excess DTPA without Zn in previous studies. Copper uptake was also inhibited by ZnDTPA, and to a lesser extent by ZnEDTA, but this may be explained by the unavailability of chelated Cu in solution culture. The high levels of chelated Zn applied were not greatly available for uptake except that both sources promoted large accumulation in primary leaves. It was postulated that primary leaves are a major sink for chelating agents that are taken up by plants.

It is well known that Fe chelates and chelating agents do inhibit Mn uptake by plants and often induced Mn deficiency (Wallace et al., 1976; Wallace, 1980a, b). High levels of excess chelating agents, especially DTPA, inhibit plant uptake of Zn, Cu and Mn but not always of Fe (Halvorson and Lindsay, 1977).

The major purpose of the experiment reported here was to determine if a high level of ZnDTPA would result in greater Zn uptake by plants than the same level of ZnEDTA and perhaps result in toxicity.