Peppermint (Mentha piperita L.) is a herbaceous, perennial and essential oil bearing plant belonging to the Lamiaceae family. Peppermint’s essential oil is used extensively in food, pharmaceutical and cosmetic industries. This study was conducted to evaluate the effects of irrigation with saline water and paclobutrazol (PBZ) treatment on growth, total phenols, mineral and essential oil content of peppermint. The treatments included four salinity levels of seawater (0.6, 2, 4 and 8 ds/m) and four concentrations of PBZ (0, 15, 30 and 60 ppm) as foliar spray. The results revealed that plant height, leaf area, dry herb yield, K+ content of leaf and essential oil yield decreased with increasing salinity level. The total phenols, leaf Na+ and Cl - content showed a significant enhancement under salinity stress. There were no significant differences for essential oil content among 0.6, 2 and 4 ds/m treatments but salinity significantly reduced essential oil content in 8 ds/m. PBZ-treatment decreased the plant height and leaf area in salt-stressed and non-stressed plants. Essential oil content was not significantly affected by PBZ-treatment. Application of PBZ ameliorated the negative effects of salinity on dry herb and essential oil yield. PBZ treatment reduced the accumulation of harmful Na+ and Cl - ions while increased total phenols and leaf K+ contents. Overall, the findings of this study showed that adverse effects of salt stress on the growth and essential oil production of peppermint can be mitigated by foliar spray of PBZ.
