Effect of foliar application of chitosan on some physiological characteristics of ‎Mentha spicata L. under deficit irrigation stress

The purpose of this experiment was to investigate the effect of deficit irrigation and chitosan on some physiological traits of Mentha spicata L. This experiment was conducted in a completely randomized block design in a split plot arrangement with three replications in University of Zanjan. The experimental treatments were irrigation at two levels (100% and 60% field capacity) as the main factor and chitosan treatment at three levels (0, 50 and 100 mg/l) was considered as a sub factor. The results showed that spraying with chitosan increased chlorophyll content. The highest chlorophyll content (1.240 mg gr-1 f.w) was obtained at 100 mg/l chitosan under complete irrigation conditions (100% field capacity). The spraying application of 100 mg/l chitosan and deficit irrigation conditions (60% field capacity) caused the highest amount of carotenoids (0.45 mg gr-1 f.w), phenol (9.989 mg gr-1 f.w), flavonoid (6.993 mg gr-1 f.w) and proline (23.96 mol gr-1 fw). The highest level of antioxidant activity (91.16%) was observed in 50 mg/l chitosan under deficit irrigation. Also, deficit irrigation and chitosan had a positive effect on the essential oil yield, so that the highest essential oil yield (10.44 kg/h) was obtained at 100 mg/l chitosan concentration and under deficit irrigation conditions. Overall, the results showed that chitosan treatment had positive effects on drought stress and non-stress conditions and improved the negative effects of drought stress.