The Effect of Various Sources of Iron on the Nitrate Accumulation in Lettuce (Lactuca sativa L.)

High nitrate concentrations, especially in leafy vegetables, is a great threat to human health. Various factors play a role in reducing nitrate accumulation in vegetables, one of which is the availability of iron. The purpose of this study was to compare the effect of different sources of iron on the accumulation of nitrate in lettuce in hydroponic system. Therefore, the experiment was performed in a completely randomized design with 4 treatments and 5 replications. Treatments included different sources of iron including iron sulfate, iron chelate (Fe-EDTA) and iron amino chelate with the same iron concentration of 20 μM. An iron free solution was also considered as control. The results showed that iron amino chelate application increased root dry weight (138%), shoot dry weight (59%), stomatal conductance (80%), photosynthesis rate (107%), chlorophyll content (91%), Fv/Fm (60%) and iron concentration of shoots (113%) as compared to the control. Also, iron amino chelate increased the activity of nitrate reductase (168%), nitrite reductase (33%) and glutamine synthetase (67%) enzymes compared to the control. Application of iron amino chelate, iron chelate and iron sulfate reduced the nitrate concentration by 55%, 11% and 18% compared to control, respectively. Generally, the results showed that the application of iron amino chelate reduced nitrate accumulation by increasing the activity of enzymes involved in nitrate metabolism. According to the results, iron amino chelate can be used to reduce nitrate concentration and increase lettuce yield in hydroponic cultivation.