Specificity of iron transport in iron-stressed sugar beet plants: evidence for preferential accumulation of cobalt in the presence of iron

Abstract

Cobalt treatment of iron-stressed sugar beet plants resulted in leaf cobalt concentrations nearly three times as high as in cobalt-treated control plants. When iron-stressed plants were treated with cobalt and iron together, cobalt was transported into leaves in preference to iron. The transport system in iron-stressed sugar beet appears to be relatively specific for iron and cobalt because iron-stressed plants supplied with manganese, zinc, and copper did not transport these elements in similarly enhanced amounts. Measurements of metal contents of chloroplasts isolated nonaqueously showed that both cobalt and iron were readily transported into chloroplasts (and therefore the leaf symplast) within 48 h. The implications of these results on the mechanism of iron transport across the root plasmalemma are discussed.