Mechanism of iron reduction by roots of Phaseolus vulgaris L.

Abstract

Iron‐deficient roots of Phaseolus vulgaris L. can reduce electron acceptors such as ferricyanide, dichlorophenolindophenol and phenazine methosulfate at increased rates compared to iron‐sufficient control plants. This indicates a trans‐plasma membrane electron transfer for Fe(III) reduction.

The high Fe(III) reduction capacity can be completely inhibited by Nitro‐Blue Tetrazolium salt (Nitro‐BT) with concomitant formation of the blue reduced precipitate within the epidermis cells of the youngest root parts. Root respiration is not impaired by Nitro‐BT. The intracellular Nitro‐BT reduction can largely be prevented by excess extracellular Fe(III)EDTA. Iron‐sufficient roots reduce Nitro‐BT at a much slower rate.

We conclude that cytosolic NADH or NADPH is the cellular electron donor for the extracellular Fe(III) reduction.

Key words:

• iron‐deficiency
• ferric reduction
• tetrazolium reduction
• trans‐plasma membrane electron transfer