Uptake and transport of iron ions (Fe+2, Fe+3) supplied to roots or leaves in spinach (Spinacia oleracea L.) plants growing under different light conditions

In experiments carried out in a phytotron using aqueous cultures, there was investigated the effect of root or foliar application of different types of iron salts on spinach plant productivity, leaf and root iron content as well as the rate of transport of iron from the roots to the leaves. Plants were grown in Hoagland's solution with a single concentration at two fluorescent light intensities: 290 and 95 µmol × m-2 × s-1 PAR. To fertilize the plants, iron was supplied at a dose of 25 mg Fe in the nutrient solution or as foliar sprays using the following salts: 1 – Fe 0; 2 – FeCl2 × 4H2O; 3 – FeCl3 × 4H2O; 4 – FeSO4 × 7H2O; 5 – Fe2(SO4)3 × nH2O; 6 – Fe-Cit.The obtained results showed that the productivity of spinach plants treated with FeCl2 and FeSO4 using foliar sprays and of those fed with Fe-citrate (Fe-Cit) through the roots was significantly higher than in the case of the other salts used. Root application of the salts used had a significant effect on root iron content, whereas their foliar application significantly affected leaf iron content. In this respect, ferrous salts were generally the most beneficial, while ferric salts were the least beneficial. The rate of transport of iron to the leaves, irrespective of the method of its application, was clearly higher for ferrous salts and Fe-Cit than for ferric salts. The free proline content in the leaves of plants not fertilized with Fe was 2–4 times lower than in plants supplied with this nutrient. An irradiance of 290 µmol × m-2 × s-1 had a positive effect on plant productivity and root Fe content..