Uptake of 59Fe from soluble 59Fe-humate complexes by cucumber and barley plants

The capability of cucumber (Cucumis sativus L., cv. Serpente cinese), a Strategy I plant and barley (Hordeum vulgaris L., cv. Europa), a Strategy II plant to use Fe complexed by a water-soluble humic fraction (WEHS) extracted from a peat, was studied. Uptake of 59 Fe from 59 Fe-WEHS by cucumber plants was higher at pH 6.0 than at pH 7.5. Roots of intact cucumber plants were able to reduce the Fe III -WEHS complex either at pH 6.0 or 7.5, rates being higher in the assay medium buffered at pH 6.0. After supply of 59 Fe-WEHS, a large pool of root extraplasmatic 59 Fe was formed, which could be used to a large extent by Fe-deficient plants, particularly under acidic conditions. Uptake of 59 Fe from 59 Fe-WEHS by Fe-sufficient and Fe-deficient barley plants was examined during periods of high (morning) and low (evening) PS release.[...]