LAUSR

Abstract 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 characteristics 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 conditions. 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 photosynthetic 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 conclusion, 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.