Abstract

The aim of this study was investigating the effect of irrigation levels (irrigation after 70, 100, 130 and 160mm evaporation from pan) and mycorrhizal fungi species (Mycorrhiza non-application, Rhizophagusintradices, Funneliformismosseae, G. hoei and combined application of all three species) on growth and physiological attributes of lemon balm over two years and based on combined analysis of variance with a completely randomized block design. The highest yield achieved with from irrigation after 100mm evaporation + application of all three species of mycorrhizal fungi. Irrigation after 100mm evaporation increased this trait by 33% compared to irrigation after 70mm evaporation due to increase in essential oil percentage under dehydration conditions, but dehydration increment a decrease in each two components of essential oil yield (essential oil percentage and dry matter yield) led to a significant decrease in essential oil yield. Dehydration led to an increase in proline content and antioxidant activity. In the present study, despite the diminishing effect of dehydration, somewhat the mycorrhizal use was able to reduce the negative effect of dehydration. In general, given to the results and considering the economic importance of essential oil yield, lower water deficit stress and mycorrhizal application can increase the lemon balm essential oil yield, but planting this plant under severe water deficit condition drastically can decrease essential oil yield.

Keywords:Lemon balm; Dehydration; Mycorrhizae; Essential oil yield