Scientia Horticulturae 217 (2017) 114–122 Contents lists available at ScienceDirect Scientia Horticulturae journal h om epa ge: www.elsevier.com/locate/scihorti Exogenous application of chitosan on biochemical and physiological characteristics, phenolic content and antioxidant activity of two species of basil (Ocimum ciliatum and Ocimum basilicum) under reduced irrigation A. Ghasemi Pirbalouti a,b,∗ , F. Malekpoor a,c , A. Salimi c , A. Golparvar d a Medicinal Plants Department, Shahrekord Branch, Islamic Azad University, Shahrekord, 88146, Iran b Medicinal Plants Program, College of Natural Sciences, Massachusetts University, Amherst, 01003, MA, USA c Department of Plant Biology, Faculty of Biology Science, Kharazmi University, 15719-14911, Tehran, Iran d Department of Agronomy and Plant Breeding, College of Agriculture, Isfahan (Khorasgan) Branch, Islamic Azad University, Isfahan, Iran a r t i c l e i n f o Article history: Received 10 August 2016 Received in revised form 17 January 2017 Accepted 18 January 2017 Keywords: Chitosan Ocimum basilicum Ocimum ciliatum Water deficit stress Growth a b s t r a c t Chitosan is a biopolymer with various industrial, medicinal, pharmaceutical, and agricultural applications. Effects of exogenous application of chitosan, a marine polysaccharide with unique bioactive properties, under normal irrigation and stressed conditions on morphology, physiology and biochemical character- istics of two species of sweet basil, including Ocimum ciliatum and O. basilicum in a pot experimental at semiarid and cold climate, southwestern Iran were investigated. Treatments comprised control, 0.0, 0.2, and 0.4 g/L chitosan applied to plants under normal irrigation, slight and mild drought stress con- ditions. Results indicated that drought stress had significant effects on some morphology, physiology and biochemical characteristics. In both species of basil, drought stress decreased the content of pho- tosynthetic pigments and growth parameters. Exogenousapplication of chitosan (in particular 0.4 g/L) increased plant growth parameters in both species of basil under stressed or non-stressed conditions as compared to untreated plants. In addition, results indicated that the different levels of chitosan had significant effects on total phenol content and antioxidant activity of the extracts of two species. In con- clusion, it is suggested that chitosan could be a promising material used to reduce the harmful effect of water stress on the growth parameters of basil plants and as a whole, treatment with chitosan partly could alleviate the effect of drought stress. © 2017 Elsevier B.V. All rights reserved. 1. Introduction Ocimum L. (basil) is considered as one of the largest genera of the family Lamiaceae and comprises annual, perennial herbs and shrubs native to the tropical and subtropical regions (Moghaddam et al., 2014). Most culinary and ornamental basils are cultivars of sweet basil (O. basilicum), which it widely cultivated in many coun- tries. O. ciliatumas a main species of Iranian herbs (Makari and Kintzios, 2008; Moghaddam et al., 2015) is grown in home gar- dens and leaves and herbaceous parts of plants used as medicinal, vegetable and culinary herb (Moghaddam et al., 2011). ∗ Corresponding author at: Medicinal Plants Department, Shahrekord Branch, Islamic Azad University, Shahrekord, 88146, Iran. E-mail addresses: ghasemi@iaushk.ac.ir, aghasemipir@psis.umass.edu (A. Ghasemi Pirbalouti). In arid and semiarid regions, the growth of medicinal and aromatic plants is influenced by various environmental factors especially water deficit stress (Bettaieb et al., 2009; Ghasemi Pirbalouti et al., 2014). Drought is a major environmental stress affecting on plant morphology, physiology and biochemistry char- acteristics (Shao et al., 2008). Water deficit stress inhibits the photosynthesis of plants, causes changes in chlorophyll contents and components and damage to the photosynthetic apparatus (Nayyar and Gupta, 2006). Overall, under drought stress conditions, fresh and dry weights of the herbs, proline, total carbohydrate and protein contents were significantly influenced (Khalid, 2006). Plants under water stress can avoid the harmful of drought throw several ways among them stomata closure, leaf rolling, osmotic adjustments, reductions and consequently decreases in cellular expansion, and alterations of various essential physiologi- cal and biochemical processes that can affect growth, productivity and yield quality (Farouk and Amany, 2012; Hefny, 2011). In this http://dx.doi.org/10.1016/j.scienta.2017.01.031 0304-4238/© 2017 Elsevier B.V. All rights reserved.