Effects of increasing iron application doses on growth and some nutrient element concentration of spinach

Foods with a low nutritional value causes to some health problems related to insufficient intake of the elements. One of these elements is iron (Fe) and adequate daily intake of it is important for humans. Consumption of green leafy plants which were fortified with iron could be the way for humans who suffer from iron deficiency. However, up taken amounts of the other nutrients in plants are also important and they must be found at optimum stage and with a harmony between each other. Although the appropriate amounts of them are necessary for plants and also for human and animal health, excess amounts are harmful. Therefore, to determine the effects of increasing doses of Fe on the growth and nutrient element uptake of spinach (Spinacia oleracea L.) a greenhouse research was set up. Increasing doses of Fe (30, 60, 90, 120 and 150 µM) were applied to spinach cultivars 'Matador', 'Reis' and 'Greenstar' in a re-circulated hydroponic system. Increasing Fe doses had statistically significant (p < 0.01) effects on spinach cultivars. Iron, stimulated the plant growth, the dry matter yield, SPAD values and the nutrients uptake of both shoots and roots of spinach up to 120 µM Fe doses (p < 0.01). However the effect of highest dose (150 µM) of Fe was found negative. Accumulation of especially the Fe, Cu and Mn was occurred in the roots with high amounts of Fe. In contrast to the micro elements the insufficient amounts of Fe inhibited the translocation of Mg to shoots and an accumulation of Mg was observed in the roots of spinach with low amounts of Fe. Because of the contrary relations with the other nutrients, a special attention must be paid during fortifying the plants with iron.