ABSTRACT
Background: Drought stress reduces growth and changes metabolites of medicinal plants. Mycorrhizal fungus in interaction with phosphorus can modify drought stress
Objective: Study the effects of drought stress, mycorhiza and phosphorus fertilizer on growth indexes, quantity and quality of essential oil of medicinal plant Dracocephalum moldavica L.
Methods: This study was done on the base of factorial experiment in randomized complete block design with five replications. The factors were consist of three level of drought stress 95% Fc, 65% Fc and 35% Fc, three level of mycorrhizal inoculation [non-inoculated, Glomus mosseae and Glomus intraradiceae] and two level of phosphorus fertilizer [0, 100 kg/ha]
Results: Interaction effects were significant between drought stress, mycorhiza and phosphorus factors in all measured attributes at the 1% level. The highest fresh weight of plant and leaf were related to no drought stress condition [95% of field capacity], application of mycorhiza and phosphorus fertilizer treatments. The highest number of flowers, fresh weight of root, and essential oil percent were recorded in mild drought stress [65% of field capacity], mycorrhiza inoculation and application of phosphorus fertilizer. The lowest amount of all of above mentioned traits obtained in severe water stress, without Mycorhiza and phosphorus fertilizer treatments. The highest content of 6-methyl- 2-phenylindole and Z-citral in essential oil were obtained with no drought stress treatment. The mild water stress with application of G. intraradices increased the geranyl formate, geranyl acetate and caryophyllene oxide in essential oil
Conclusion: Application of two mychorhiza strains in severe water stress can increase physiological yield and essential oil percent of Deracocephalum moldavica in about 45- 100%. The essential oil was increased even in no water stress with application of mychorhiza strains