Impact of foliar application of amino acids on total phenols and sugars content of mentha piperita 'Granada'

Abstract

The aromatic amino acids (phenylalanine, tyrosine, tryptophan) are not only components of protein synthesis in plants, they are also involved in a cellular reactions. Therefore, they influence a number of physiological processes. Several studies have shown that spraying with amino acids can increase sugars content also they can be used as precursors for phenols synthesis stimulation in plants. Sugars play important roles as both nutrients and regulatory molecules throughout plant life. Mint plants are one of widely used herbs for their aromatic and medical properties in the world. Many mint species have been used traditionally as a food seasoning, mainly in fish recipes, curd and meat dishes, also can be used as tea. The aim of this study was to investigate the influence of aromatic amino acids on sugars and phenols content of M. piperita ˈGranada' plants. Mints were planted at Vytautas Magnus University Agriculture Academy experimental station in 2017. Mint plants were sprayed with aromatic amino acids phenylalanine, tryptophan and tyrosine at two concentrations (100 mg l-1 and 200 mg l-1) three times with 15 days interval. The first spraying was started on 21 and harvested on the 65 BBCH stage of mints development. The sugars and phenols content was determined by HPLC method. The results showed that application of amino acids had positive influence on fructose, glucose and sucrose and total phenols content in M. piperita 'Granada' plants, but the highest amount of fructose was determined in mint leaves sprayed with water 34.81g 100g-1 (DW). Tryptophan at 100 mg l-1 concentration and phenylalanine at 200 mg l-1 concentration 2-fold increased sucrose content in mint plants. The total phenol content fluctuated from 175.26 mg 100g-1 to 300.37 mg 100g-1 (DW) and highest amount was determined in mint leaves sprayed with phenylalanine. It was established positive strong correlation (r=0.66) between glucose and total phenols content.