Effect of Amino Acids Combination on the Quantitative and Qualitative Characteristics of Garlic (Allium Sativum L.)

Garlic is one of the most widely employed condiments in cooking. It has been found to possess important biological properties with high therapeutic potential, which is influenced by the mode of its utilization, preparation, and extraction. It has been attributed with antioxidant, anti-inflammatory, and immunomodulatory capacities. Garlic, in particular its organosulfur compounds, can maintain immune system homeostasis through positive effects on immune cells, especially by regulating cytokine proliferation and expression. Amino Acids are the building units of proteins. There are about 300 amino acids occur in nature. Only 20 of them enter in proteins synthesis. Amino acids are essential nutrients for plant growth. Due to the characteristics of amino acids, they have a unique promotion effect on plant growth, especially on photosynthesis. Amino acids are good organic nitrogen sources in plant. They can be directly absorbed and utilized by cells, promote protein synthesis, and have a good effect on the growth. Spraying or irrigating amino acid nutrient liquid fertilizer can increase the element of various nutrients required in the plant, aggravate the accumulation of dry matter and the speed and quantity of the operation from the root or leaf to other parts, and adjust the proportion and balance of macroelement, trace element and other nutrients. Thus, the normal growth of the plant will be regulated. Many studies proved that amino acids play a positive role in enhancing the plant yield and quality when they are sprayed at different growth stages. This research was done to study effect of different amino acids compound on the quantitative and qualitative characteristics of garlic.

The experiment was performed at three replications in a completely randomized blocks design in the Research Field of Tarbiat Modares University during the 2018-19 growing season. The experimental treatments included: 1) Arginine + Aspartic acid 2) Arginine + Valine 3) Arginine + Tyrosine 4) Arginine + Leucine 5) Aspartic acid + Valine 6) Aspartic acid + Tyrosine 7) Aspartic acid + Leucine 8) Valine + Tyrosine 9) Valine + Leucine 10) Tyrosine + Leucine 11) Trade amino acid 12) Distilled water 13) No amino acid (control).

The results showed that the maximum bulb fresh weight (13.054 t ha-1) and photosynthetic rate (10.58 µmol m-2s-1) was obtained from the aspartic acid + leucine. Also, the highest catalase activity was observed in the use of arginine with aspartic acid (9064 U mgFW-1), while the peroxidase activity was higher in the aspartic acid + valine (517 U mgFW-1), arginine + and tyrosine (511 U mgFW-1) and arginine + leucine (496 U mgFW-1) treatments.

In general, it seems that foliar spraying of amino acids increases the plant's energy efficiency (plant energy storage for the production of amino acids) and also increases the photosynthesis rate and thus helps the plant to increase the yield of the plant. Among the investigation of different combinations of amino acids, the combination of aspartic acid and leucine increased the performance more than other combinations and is introduced as the best treatment.