Middle East Journal of Agriculture Research ISSN 2077-4605 Volume : 05 | Issue : 04 | Oct.-Dec. | 2016 Pages: 701-708 Corresponding Author: Ahmed S. H. Gendy, Department of Horticulture, Faculty of Agriculture, Zagazig University, Egypt. E-mail: shaker8873@yahoo.com 701 Improving Productivity and Chemical Constituents of Roselle Plant (Hibiscus sabdariffa L.) as Affected by Phenylalanine, L- Tryptophan and Peptone Acids Foliar Application Ahmed S. H. Gendy and Walid S. Nosir Department of Horticulture, Faculty of Agriculture, Zagazig University, Egypt. Received: 15 October 2016 / Accepted: 10 December 2016 / Publication date: 31 December 2016 ABSTRACT A field experiment was conducted at the Experimental Farm, Faculty of Agriculture, Zagazig University, Egypt, during the two consecutive seasons of 2014 and 2015 to evaluated the effect of different amino acids concentrations as foliar spray viz., phenylalanine (150 and 300 ppm), L- tryptophan (50 and 100 ppm) and peptone (500 and 1000 ppm) as well as control (sprayed with tap water) on growth, yield and its components, active ingredients expressed as anthocyanin content and some chemical constituents of roselle plant. Plants were foliar sprayed with amino acids concentrations three times at 35, 50 and 65 days after sowing. The simple experiment included seven treatments were arranged in a randomized complete block design with three replicates. Results demonstrated that different applied amino acids treatments increased the obtained values of most recorded characteristics compared to control. Furthermore, the better growth characters (plant height, branch number and total dry weight) and higher yield components (fruit number per plant, sepals and seeds yield per plant and per feddan) as well as chemical constituents of roselle sepals (nitrogen, phosphorus, potassium, protein and carbohydrates contents, total soluble solids and anthocyanin content),also , total chlorophyll content (a+b) in leaves could be obtained by spraying L- tryptophan at 100 ppm. Key words: Roselle, Phenylalanine, Tryptophan, Peptone, Growth, Yield, Chemical constituents Introduction Roselle (Hibiscus sabdariffa L.) is a tropical and subtropical annual herbaceous plant belonging to the family Malvaceae. In North Africa, especially in Egypt, it is known as Karkadeh. Roselle could be native to Africa and is widely cultivated throughout many countries such as India, Sudan, Egypt, and Mexico (Tindall, 1983). The roselle calyces contain organic acids (tartaric, oxalic, malic, ascorbic and succininc acids), glucose, ß-carotene and lycopne, in addition to two types of anthocyanin, i.e. delphinidin and cyandin (Peng- Kong et al., 2002 ; Peng-Kong et al., 2003). Roselle has also many medicinal properties since it is used as digestive, choleretic, antibilious, laxative, diuretic, hypotensive, antiscorbutic. Moreover, the seeds contain sterols, including 3.2% ergosterol (Khare, 2007).The calyx extraction has a great therapeutic action for blood pressure (Hassan, 2009). Amino acids as organic nitrogenous compounds are the building blocks in the synthesis of proteins, Davies (1982). Amino acids are particularly important for stimulation cell growth. They act as buffers which help to maintain favorable pH value within the plant cell, since they contain both acid and basic groups; they remove the ammonia from the cell. The regulatory effect of amino acids on growth could be explained by the notion that some amino acids e.g. phenylalanine can affect plant growth and development through their influence on gibberellins biosynthesis (Walter and Nawacke, 1978). L-Tryptophan is known to be a physiological precursor of auxins in higher plants. It is investigated that L-Tryptophan has more positive effect on plant growth and yield as compared to pure auxins (Zahir et al., 1999). L-Tryptophan is an amazing amino acid. It may act as an osmolyte, ion transport regulator, modulates stomatal opening and detoxify harmful effects of heavy metals (Rai, 2002). Peptone promoted growth parameters and flowering parameters (number of flower/plant, flower diameter and fresh and dry weights of flowers) as well as chemical constituents, Ibrahim et al. (2010).