Maintains the supply of reduced ferredoxin under non-photosynthetic conditions. H(+) + NADP(+) + 2 reduced [2Fe-2S]-[ferredoxin] = NADPH + 2 oxidized [2Fe-2S]-[ferredoxin] A number of isoforms are produced. According to EST sequences. Expressed in shoots and roots. Less abundant in roots than RFNR2. Up-regulated by nitrate in roots while down-regulated in shoots. Belongs to the ferredoxin--NADP reductase type 1 family.