2703 Potential benefits of foliar application of chitosan and Zinc in tomato Azam Salimi 1 , Zahra Oraghi Ardebili 2 *, Maryam Salehibakhsh 1 1. Department of Biology, Kharazmi University, Karaj, Iran 2. Department of Biology, Garmsar Branch, Islamic Azad University, Garmsar, Iran _______________________________________________________________________________ Abstract The current study was carried out to investigate the efficiencies of foliar supplementations of Zinc and/or chitosan on the growth and physiology of tomato (Lycopersicon esculentum L.) and clarify the involved mechanisms. Seedlings were sprayed with three concentrations (0, 50, and 100 mgL -1 ) of chitosan and/or three levels of Zinc sulfate (0, 50 and 100 mgL -1 ). The application of Zn and/or chitosan led to increases in shoot fresh mass, about 31%, over control. In comparison with the control, enhancement (approximately 28.5%) in shoot dry mass resulted from the single application of chitosan or zinc while this percentage reached to about 45% for seedlings simultaneously treated with the chitosan and Zn supplements. About 29% improvements in the plant height resulted from the chitosan and/or zinc. Higher amounts of chlorophyll contents were recorded in the chitosan and/or zinc-treated plants, among which the highest levels were found in the combined treatments. Simultaneous applications of chitosan and zinc were the most effective treatments to induce PAL (phenylalanine ammonia lyase) activity (about 64%) when compared to the control. Chitosan and/or zinc treatments, especially the latter, significantly promoted the activity of (SOD) superoxide dismutase enzyme (about two folds), over the control. Also, increases in proline contents was provoked by applying the treatments. Foliar supplementations of these compounds as an eco-friendly solution may have considerable potential to act as exogenous elicitors and trigger various physiological traits, thereby improving plant growth and resistance under abiotic stress conditions. Keywords: Bio-fortification; Chitosan; elicitor; foliar; Lycpersicon Salimi, A., Z. Oraghi Ardebili and M. Salehibakhsh. 2019. 'Potential benefits of foliar application of chitosan and Zinc in tomato'. Iranian Journal of Plant Physiology 9 (2), 2703-2708. ________________________________________________________________________________ Introduction Chitosan is regarded as a biodegradable, low toxic, and cost effective substance formed by deacetylation process of chitin (Iriti et al., 2009), applied in various food, agriculture, and medicine industries (Pichyangkura and Chadchawan, 2015). Antimicrobial characteristics of this biopolymer have been well known. Interestingly, it may act as an exogenous elicitor to improve plant immunity (Pirbalouti et al., 2017). Various strategies have been investigated to find the eco-friendly solutions for improving crop protection, among which chitosan is a suitable candidate, taking into account sustainable agriculture and environmental issues (Asgari-Targhi et al., 2018). Zinc (Zn) deficiency in soil, especially in calcareous soils has been proposed as a global concern (Subramanian et al., 2014) and an important limiting factor affecting plant growth *Corresponding author E-mail address: zahraoraghi@yahoo.com Received: June, 2018 Accepted: November, 2018