Study the effect of salicylic acid pretreatment on germination and early growth of black cumin (Nigella sativa) under salinity stress

The assessment of medicinal plants tolerance is very important for cultivation of them in saline areas. Salicylic acid is a growth regulator which its role was investigated in plants tolerance to environmental stresses such as salinity.In order to evaluate the effects of salicylic acid on early seed germination andseedling growth of black cumin (Nigella sativa) under salt stress, an experimentwas conducted in a factorial arrangement based on a completely randomized design with 15 treatments and three replications. The experimental treatments were including different concentrations of salicylic acid (0, 0.25, 0.5, 0.75 and 1 mM) and salinity (0, 50 and 100 mM). The seeds of black cumin which were primed with different concentrations of salicylic acid for 24 hour, for germination test under salt stress, they transferred into sterile petri dishes which contain 10 ml NaCl. Results revealed a significant reduction in germination percentage and rate, seedling dry weight, seed vigor index, radicle length, radicle fresh and dry weight, shoot length, shoot fresh and dry weight with increasing salinity stress. Pretreatment with salicylic acid caused an increase of plant tolerance to salinity stress.  The application of salicylic acid greatly caused the increment of germination percentage and rateand enhanced fresh and dry weight of black cumin under salt stress. It seems that higher concentrations of salicylic acid (0.5 up to 1 mM) caused an increase of all mentioned traits under normal and stress conditions.