Study of anatomical structure of Melissa officinalis and the effects of drought stress and salicylic acid treatment on its morphological and molecular characteristics

Melissa officinalis L. is an important medicinal plant. Due to the lack of developmental studies in this plant, the present study was first used to identify the structure and then how to respond to drought stress (0, fc 2/3, fc 1/3) and the effect External application of salicylic acid (0, 0.7 and 1.5 mM). For this purpose, the seeds of lemon balm were cultured in appropriate pots after sterilization .At the same time, a number of untreated pots were cultivated for anatomical studies. Experiments were performed as split plot split factorial with three replications. The description showed the similarity of this plant with other plants of the family of Lamiaceae, and with the advancement of the stage of development, gradually, the thickness of the sclerenchyma tissue was increased, In the study of stresses on histology, decreasing the diameter of the xylem and increasing the length of the trichomes, salicylic acid treatment was highly desirable in reducing the effects of drought stress. Molecular studies using the qRT-PCR technique showed that the expression of tyrosine aminotransferase (TAT) gene was not significantly altered under stress conditions and the highest expression was observed in drought stress conditions of 2/3 fc and salicylic acid 0.7 mM. It can be concluded that salicylic acid treatment has a positive effect on histological studies in plants under drought stress, but has no significant effect on TAT gene expression in plants under drought stress.