Effect of osmopriming on seed germination of Lemon balm (Melissa officinalis L.) under salinity stresses

With regard to the importance of Melissa officinalis L. as a medicinal plant and abundance of saline soil and water in the country, the current research was conducted to study the effect of osmopriming on seed germination of Melissa officinalis under salinity stress in two separate experiments. The aim of the first experiment was to determine the best osmopriming conditions for seeds of Melissa officinalis carried out in a completely randomized design. The treatments were combination of osmotic potential of polyethylene glycol (PEG) with four levels (-4, -8, -12 and -16 bar), duration of priming with three levels (3, 5 and 7 day) and temperature of priming with two levels (25 and 30/20oC). The results showed significant differences among osmopriming treatments with regard to the germination percentage, germination velocity and radicle length. Mean comparisons showed that osmotic potential treatment of -16 bars in 5 days and 25oC significantly increased the germination percentage and germination velocity compared with other treatments. The aim of the second experiment was to study the effect of osmopriming on seed germination of Melissa officinalis under salinity stress based upon a factorial experiment in a completely randomized design with three replications. The treatments were water salinity (control, 4, 8 and 12 dS/m) and type of seeds (control and primed seeds). The results indicated that primed seeds in all salinity levels had higher germination percentage, germination velocity and radicle length compared to non-primed seeds. According to the results, the interaction effect of salinity and seed treatments was significant with regard to the germination percentage, germination velocity and radicle length.