Iron and nitrate assimilation in blueberries (Vaccinium Spp.)

The uptake and assimilation of iron (Fe) and nitrate (NO₃ −) or ammonium (NH₄+) were studied in the cultivated southern highbush blueberry (Vaccinium corymbosum L. interspecific hybrid ‘Misty’) and a wild species (V. arboreum Marsh.). Blueberries were grown hydroponically in either NO₃− or NH₄+ at pH 5.5 or in NO₃− at various pHs and Fe concentrations. Iron and NO₃− or NH₄ + uptake rate, root and leaf ferric chelate reductase (FCR) activity, and root nitrate reductase (NR) activity were quantified.; The results showed that blueberries can take up both nitrogen (N) forms but NH₄+ uptake rates were greater than NO ₃− uptake rates. V. arboreum had greater root NR activity than V. corymbosum except when the experiments were conducted during the winter (October to February in Gainesville, Florida). The greater root NR activity in V. arboreum was not always reflected in increased N uptake and/or growth. V. corymbosum had potentially greater root FCR activity than V. arboreum but this was not reflected in increased Fe uptake rates. In general, neither V. corymbosum nor V. arboreum had the ability to increase root FCR activities under Fe deficient conditions compared with Fe sufficient conditions. Thus, both species should be classified as Fe-inefficient genotypes. Root FCR activity and Fe uptake rate increased as external Fe concentration increased.; Under Fe sufficient conditions, root FCR activity was greater at pH 6.5 compared with pH 5.5, but no pH effect on leaf FCR activity, root NR activity or NO₃− uptake rates were found in either species. There were no severe symptoms of leaf chlorosis in either species at this present study, although there was a reduction in leaf area at pH 6.5 compared with 5.5.; V. arboreum had greater leaf FCR and root NR activities compared with V. corymbosum under NO₃− conditions. The ability of V. arboreum to utilize Fe and NO₃− more efficiently explain why this species can thrive in mineral soils where NO₃− is the dominant N form.