Flavocytochrome that transfers electrons across the plasma membrane to reduce ferric iron chelates to form soluble ferrous iron in the rhizosphere. May be involved in the delivery of iron to developing pollen grains. Acts also as a copper-chelate reductase. Involved in glycine betaine-mediated chilling tolerance and reactive oxygen species accumulation. 2 a Fe(II)-siderophore + H(+) + NAD(+) = 2 a Fe(III)-siderophore + NADH Expressed in the epidermal cells of the roots. High expression in lateral roots and root hairs. Detected in leaves, stems, siliques and in flowers in anthers and styles. Circadian-regulation. Up-regulated in roots by iron deficiency, carbon monoxide and by treatment with glycine betaine. Down-regulated by zinc, cadmium and cytokinin. Not regulated by copper. The C-terminus is probably located inside the membrane. Impaired growth on media with no added iron. No response to glycine betaine in chilling assays. Post-transcriptionally regulated by iron. Coordinately regulated with the iron transport protein IRT1. Belongs to the ferric reductase (FRE) family.