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Ferric chelate reduction (FCR) activity of roots and leaves was determined in the grapevine rootstock 140 Ruggeri under iron (Fe)-deficient and Fe-sufficient conditions. Micropropagated plants were subjected to 0 or 40 μm Fe(III) EDTA in hydroponic culture. After 10 days of treatments, Fe-deficient plants had a lower level of root FCR activity and chlorophyll content compared with Fe-sufficient plants. Iron supply (20 μm) to Fe-deficient plants caused a rapid increase of root FCR activity (five times higher than initial values) and plants restored leaf chlorophyll content, whereas those not supplied with Fe retained reducing activity at low levels. In Fe-sufficient plants, root FCR activity decreased gradually when Fe was removed from the nutrient solution, reaching the same low levels as the Fe-deficient plants. Iron-sufficient plants displayed constitutively elevated root-reducing capacity for 3 weeks in culture under Fe-sufficient conditions. In Fe-deficient plants, root FCR activity was confined at the apical region of the lateral roots, whereas in Fe-treated plants, activity was detected along almost the whole length of the lateral roots. Root hair development, from the aspect of length and density, proved to be independent of the Fe status of rootstock plants. Leaf FCR activity was measured in mesophyll protoplasts from in vitro-growing Fe-deficient and Fe-sufficient plants. Mesophyll protoplasts reducing activity in Fe-deficient plants appeared to be decreased 43.5% or 40.3%, on a protoplast number or protein basis, respectively, in comparison with that in protoplasts from Fe-sufficient plant leaves. The results suggest that Fe is one of the agents inducing root and leaf FCR activity in grapevine rootstock 140 Ruggeri, altering furthermore its localization pattern in roots.

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