Comparison of efficiency of different Fe sources on growth and physiological characteristics of lettuce under alkaline conditions in hydroponic system

In order to investigate the effect of different iron (Fe) sources on lettuce yield, under the sodium bicarbonate stress conditions, a greenhouse experiment was carried out with two factors including Fe source in three forms (Fe-EDDHA, Fe nano chelate and nanofertile) and sodium bicarbonate at three levels (0, 5, and 10 mM) with three replications. Three weeks after transplanting, seedlings were treated with sodium bicarbonate for 30 days. Results showed that dry weight of shoot and root decreased significantly by elevating the sodium bicarbonate concentration in nutrient solution. In response to higher sodium bicarbonate concentrations, chlorophyll a, b and maximal quantum yield of PSII photochemistry (Fv/Fm) decreased in all Fe treatments, while, the lowest reduction of these parameters was observed in plants grown with Fe-EDDHA. Sodium bicarbonate stress caused a reduction in Fe concentration of leaves and roots, such that at 10 mM sodium bicarbonate concentration, and nanofertile Fe source, Fe content in shoots decreased 64.88% as compared to control. Based on the obtained results, the Fe-EDDHA, due to its higher solubility and availability, has more potential to be absorbed by lettuce, and for this reason, increased growth of the lettuce. Therefore, due to the importance of Fe in nutrition of plants, application of Fe-EDDHA under alkali conditions is the best source of Fe supply for lettuce.