Determination of ferrous and ferric iron ratio in spinach plants and their relation to iron application

Two greenhouse pot experiments, namely sand culture and calcareous soil were carried out to evaluate Fe⁺⁺ /Fe⁺⁺⁺ ratio in spinach plants. Six rates of iron fertilization as ferric‐EDTA, i.e., control, 5, 15, 39 50 and 100 ppm. Fe were applied. Determination of Fe⁺⁺ and Fe⁺⁺⁺ iron is based on the fact that Fe ⁺⁺ reacts with 8 N HCl in absence of water forming tetrachloroferrate (FeCl₄)^‐ which is soluble in diethyl ether but insoluble in water, therefore, Fe⁺⁺ and Fe⁺⁺⁺ in plant tissue could be extracted and separated from each others.

Fe_T and Fe⁺⁺ content in spinach plants were increased as the soil iron applications were increased . At the mean tine, Fe⁺⁺⁺ content was only increased up to 15 ppm iron treatment. However, beyond this rate, Fe⁺⁺⁺ content was almostly tended to remain constant, despite the increased amount of total iron.

Values of Fe_T, Fe⁺⁺ , Fe⁺⁺⁺ concentration in spinach plants tissues grown in calcareous soil were significantly lower, than those obtained in case of sand culture experiment.