The effect of mycorrhiza fungus, different levels of humic acid, and salicylic acid on morphological characteristics and essentioal oil content in three cultivars of Melissa Officinalis L.

This study was performed to investigate the effect of mycorrhizal fungus and different levels of humic acid (zero, 200 and 400 mg/l) and salicylic acid (zero, 100 and 200 mg/l) on morphological characteristics and essential oil content of three cultivars Lemonella, Citronella and Varigated. Lemon balm (Melissa Officinalis L.) was implemented in 1397 in a greenhouse in northern Iran. The experiment was performed as a factorial in a completely randomized statistical design with 3 replications. Mycorrhiza and humic acid treatments were applied at the time of seed sowing and salicylic acid solution was sprayed in two stages (second and third weeks of pot cultivation). The results of this experiment showed that all treatments had a significant effect on fresh and dry weight of shoots and roots, root volume and essential oil content and among the lemon balm cultivars Lemonella cultivar had the highest morphological characteristics and essential oil content. The highest shoot dry weight, fresh and dry root weight and root volume in mycorrhiza+ humic acid 400 mg/l + salicylic acid 200 mg/l and the highest fresh weight of mycorrhiza+ humic acid 200 mg/l + salicylic acid 200 mg/l was obtained. Also, the highest amount of essential oil was observed in the treatment of mycorrhizal fungus+ humic acid 400 mg/l + salicylic acid 100 mg/l. In general, to improve the vegetative growth and the amount of essential oil of lemon balm, the application of Lemonella cultivar and application of mycorrhizal fungus with humic acid 400 mg/l and salicylic acid 200 mg/l is recommended.