The effects of amino acids fertilization incorporated to the nutrient solution on mineral composition and growth in tomato seedlings

The aim of this research was to determine the effects on growth variables and leaf mineral concentration of tomato plants watered with nutrient solutions containing amino acids. Two separate experiments were then carried out to achieve this goal. In the first experiment, plants were watered with seven different nutrient solutions consisting of half-strength Hoagland solution supplemented with single (Alanine, Serine, Phenylalanine, Tyrosine) or combined (Ala + Ser; Phe + Tyr) amino acids, each at 0.2 mM of concentration. The control nutrient solution did not have any amino acids added. Relative to the control, growth variables were not affected by the presence of amino acids. In general, the mixture of Ala + Ser increased the leaf Ca2+ concentration, and the aliphatic amino acid treatments favoured an increase in leaf K+, Fe, Cu, and Mn concentrations. In addition, amino acids with hydroxyl groups in their structure, Ser and Tyr, increased Mg2+ concentration. In the second experiment, the nutrient solutions were supplemented with 0.05 mM of the same amino acids (T1). Control plants were irrigated with amino acid-free nutrient solution (T0). The concentration of Ca2+, K+, Mg2+, Fe, Cu, and Mn in the leaf also increased due the amino acids treatment. Chlorophyll contents in the leaves and amino acids compositions in the xylem sap and leaf water relation were also determined. In conclusion, the data reported in the two experiments point out that the application of amino acids to the nutrient solution has a beneficial effect on the leaf mineral status and on the chlorophyll concentration of the leaves.