Effect of Iron-Amino Acid Chelates on Antioxidant Capacity and Nutritional Value of Soybean

Supplying a sufficient amount of available iron (Fe) for plant growth in hydroponic nutrient solutions is a great challenge. There are various Fe fertilizers to eliminate iron deficiency in crops. The chelators commonly used to supply Fe in nutrient solutions have several disadvantages and may negatively affect plant growth. The objective of the current paper was to evaluate the effects of some various Fe- chelates, (Fe-arginine, Fe-glycine, Fe-histidine, Fe-lysine, Fe-glutamine and Fe-EDTA) on the physiological properties and nutraceutical potential of soybean (Glycine max (L.) Merr.) grown in nutrient solution.

The experiments had a randomized complete block design with three replications and the treatments were arranged in factorial combination. The plants were grown in a greenhouse of Faculty of Agriculture at Lorestan University in 2018. In this study, Fe- chelates were synthesized. Then, soybean seeds were sterilized and germinated in 11 μm filter paper. Seven-day seedlings were transplanted into perlite and watered regularly with distilled water for a week. Then, Two-pair leaflet seedlings were placed in continuously aerated solution under controlled conditions of the greenhouse. Six different iron treatments (at Fe level=50 µM) were applied including: Fe-EDTA, Fe-arginine, Fe-Glycine, Fe-histidine, Fe-glutamine, and Fe-lysine. The plant leaves were collected at 10-leaves stages. The seed collection was done in the maturity of harvest (R8). Afterwards, physiological parameters, antioxidant enzymes activity and seeds quantity and quality were measured.

Fe-amino acid application significantly (P£0.05) enhanced root and shoot dry matter yield, total chlorophyll content, 1000 seed weight, seed yield, seed protein content, seed oil content, oleic acid, and number of seeds in each pod in comparison with Fe-EDTA treatment. The maximum chlorophyll content, seed protein and seed oil were observed in the Fe-glycine treatment (increased by 66.25%, 103.48% and 85.11%, respectively compared to that of control). Concentrations of ferritin, iron, zinc, and nitrogen in soybean seeds were also higher in Fe-amino acid chelate treatments compared to Fe-EDTA. The effect of Fe-amino acid chelates on the Fe content in seeds was in the order Fe-glycine> Fe-glutamine> Fe-lysine> Fe-histidine>  Fe-arginine. Catalase activity (EC 1.11.1.6) and ascorbate peroxidase (EC 1.11.1.11) significantly (P£0.05) increased in all Fe-amino acid chelates treatments compared to Fe-EDTA treatment.

According to the results, Fe-amino acid chelates could provide the required amount of iron to soybean and this resulted in seed quality enhancement. Therefore, Fe-amino acids can be used as more efficient fertilizers than Fe-EDTA in nutrient solution, and they can be used as an alternative to Fe-EDTA to supply Fe in nutrient solutions.