Synthesis of Iron-Amino Acid Chelates and Evaluation of Their Efficacy as Iron Source and Growth Stimulator for Tomato in Nutrient Solution Culture

Supplying a sufficient amount of available iron (Fe) for plant growth in hydroponic nutrient solutions is a great challenge. The chelators commonly used to supply Fe in nutrient solutions have several disadvantages and may negatively affect plant growth. In this research study we have synthesized certain Fe-amino acid chelates, including Fe-arginine [Fe(Arg)2], Fe-glycine [Fe(Gly)2], and Fe-histidine [Fe(His)2], and evaluated their efficacy as an Fe source for two tomato cultivars (Lycopersicon esculentum Mill. cvs. ‘Rani’ and ‘Sarika’) grown in nutrient solution. Application of Fe-amino acid chelates significantly increased root and shoot dry matter yield of both tomato cultivars compared with Fe-EDTA. Tomato plants supplied with Fe-amino acid chelates also accumulated significantly higher levels of Fe, Zn, and N in their roots and shoots compared with those supplied with Fe-EDTA. In ‘Sarika’, the effect of Fe-amino acid chelates on shoot Fe content was in the order Fe(His)2 > Fe(Gly)2 > Fe(Arg)2. In ‘Rani’, the addition of all synthesized Fe-amino acid chelates significantly increased activity of ascorbate peroxidase (APX) in comparison with Fe-EDTA, whereas in ‘Sarika’, only Fe(His)2 increased shoot APX activity. The results obtained indicated that using Fe-amino acid chelates in the nutrient solution could supply a sufficient amount of Fe for plant uptake and also improve root and shoot growth of tomato plants, although this increase was cultivar-dependent. According to the results, Fe-amino acid chelates can be used as an alternative for Fe-EDTA to supply Fe in nutrient solutions.