© by PSP Volume 28 – No. 12A/2019 pages 9753-9759 Fresenius Environmental Bulletin 9753 PHYSIOLOGICAL AND CYTOGENETICAL EFFECTS OF L-TYROSINE IN ALLIUM CEPA L. EXPOSED TO NaCl STRESS Dilek Cavusoglu * Isparta University of Applied Sciences, Atabey Vocational High School, Department of Plant and Animal Production, 32670, Isparta, Turkey ABSTRACT In the present work, the influences of L- Tyrosine (Tyr) on some physiological and cytoge- netical parameters in Allium cepa L., which are germinated in both salt stress and normal conditions were studied. The radicle lengths and radicle num- bers of seeds germinated in alone Tyr medium decreased partially compared to with ones the con- trol seeds germinated in distilled water medium, while their germination percentages and fresh weights statistically showed the same values. In addition, the chromosomal aberrations in root meri- stematic cells in A. cepa seeds germinated in tyro- sine alone medium showed a significant rise com- pared to ones of the control seeds germinated in distilled water. Conversely, salinity stress rather inhibited the seedling growth and seed germination of A. cepa. It also significantly increased the num- ber of chromosomal aberrations and micronuclei, which are the most effective and the simplest an indicator of chromosomal aberrations and cytoge- netical damage. But the inhibitive effects of salt on the mitotic activity, seedling growth, seed germina- tion, chromosomal aberration and micronuclei dramatically were alleviated in varying degrees by Tyr treatment. KEYWORDS: Tyrosine, mitotic index, chromosomal aberrations, seed- ling growth, salt stress, seed germination INTRODUCTION Throughout their life cycle, all plants are ex- posed to multiple stresses and main environmental factor that reduces more plant productivity is salini- ty [1]. In most of soils, the crop productivity is negatively affected owing to high NaCl content [2]. Nearly half of the irrigated land, approximately 20% of the world’s cultivated land and 7% of the world’s land area are affected by high NaCl con- tents [3, 4]. Considering another prediction, 2.1% of global dry agriculture land is affected by salinity [5]. It is possible to see the effects of salinity in semi-arid and arid regions where are effective in limited rainfall, high temperature, high evapo- transpiration associated with soil management prac- tices and poor water are major contributing factors [6]. The reason why L-Tyr (C9H11NO3, Y, α- amino-β-(p-hydroxyphenyl) propionic acid) gets its name from the Greek word “tyros” meaning cheese is its isolation the first from crude cheese proteins (casein) [7]. L-tyrosine (Tyr) is an aromatic amino acid that synthesized only in microorganisms and plants but is required for protein synthesis in all organisms. In addition, tyrosine serves as a precur- sor of a number of specific metabolites that various physiological functions like defense compounds, structural support (lignin), electron carriers, attract- ants, antioxidants. Some of these Tyr derived plant natural products are used in human nutrition as vitamin E and in medicine as morphine [8]. Alt- hough there is only one published study on role of Tyr on the seedling growth, seed germination under both saline and normal conditions, unfortunately, there is no study on the effects of said amino acid on the micronucleus frequency, mitotic activity and chromosomal aberrations in salted and normal conditions. For these reasons, this work is designed to investigate the role of Tyr in reducing of the harmful influences of salinity stress on some cyto- genetical and physiological parameters of A. cepa L. MATERIALS AND METHODS Seed, tyrosine and salt concentrations. Healty equal sizes of common onions (A. cepa L., 2n=16 chromosomes) were used. 0.175 M salt (NaCl) concentration and 100 mg/L dose of Tyr were used in the experiments. Tyr (50 capsules of 500 mg) was obtained from Solgar®. NaCl and Tyr concentrations were determined by a preliminary investigation in this study. Seed Germination. Small bulbs with a diame- ter of 3-4 cm in common onion (A. cepa L.) were sterilized with 2.5% NaOCl solution for ten minute, then washed in ultra-distilled water for 24 hours. 20