Two-heme-containing cytochrome. Catalyzes ascorbate-dependent trans-membrane ferric-chelate reduction. Able to use dihydrolipoic acid (DHLA) as an alternative substrate to ascorbate. Fe(3+)(out) + L-ascorbate(in) = Fe(2+)(out) + H(+) + monodehydro-L-ascorbate radical(in) Binds 2 heme b groups non-covalently. Homodimer. Expressed in roots, seedlings and leaves. Lower expression in flowers. Expressed in the L1 layer of the shoot apex, in the epidermis of leaf primordia and young leaves and in vascular bundles. In the differentiation zone of the root, detected in the pericycle and in the epidermis, but not in the cortex. Strongly expressed in the lateral part of the root cap and in the epidermis of the root tip, but not in the meristematic tissue. Not expressed in lateral roots. In mature embryos, expressed in the epidermis, cotyledon tips and root tips. Strong reduction in expression levels in flowers following fertilization.