The effect of foliar application of glutamine, citric acid and malic acid on the growth, quality and morphological traits of licorice)Glycyrrhiza glabra(

Licorice is one of the oldest medicinal plants that is commonly used in various industries such as pharmaceutical, food, beverages and confectionery products. this study was performed In order to evaluate the effect of foliar application of amino acids (glumaline) and organic acids (citric acid and malic acid) on growth and quality of the transplant of licorice,. glutamine (3, 6 and 9 mM), malic acid (6, 9 and 15 mM) and citric acid (3, 9 and 15 mM) and foliar application of water to be considered as control. The main traits examined in this study included;: fresh and dry weights of canopy, leaf and root, stem length and diameter, number of lateral branches, rhizome and root diameter, leaf size and trichome density and the photosynthetic pigments such as chlorophyll a, b, total, and total carotenoids. The results showed that foliar sprays of various concentrations of glutamine, malic acid, citric acid, significantly increased licorice root and shoot growth and yield as compared to the control. In the treatment of malic acid 15 mM (MA15) shoot fresh and dry weight respectively 505 and 409 %, leaf fresh and dry weight respectively 387 and 400 % and stem fresh and dry weight respectively 494 and 580% were increased compared to the control. Also the highest licorice root fresh and dry weight was in glutamine 3 mM (G3) that was increased respectively by 1124 and 1497 % compared to control. Therefore, application of appropriate levels of malic acid, citric acid and glutamine can improve the yield and quality of Licorice seedlings .