The effect of jasmonic acid (0.0, 10.0, 20.0, and 30.0~Mn) in improving salinity tolerance of the micropropagated stevia plants grown under different levels of salinity (0.0 10.0, 20.0, 30.0 and 40.0 % sea salted water) was studied. Experiments were conducted during 2003 and 2005 seasons. The obtained results clearly confirmed the absolute superiority of lower concentration (10~MlI) of jasmonic acid treatment, which significantly increased the growth parameters of stevia grown in vitro (survival percentage, shootlet length, no. of leaves I shootlet, no. of roots I plantlet and fresh as well as dry weight of shootlet) and ex vitro (shoot height, no, of leaves I plant and shoot dry weight) , yield components (leaves, stem and shoot I plant) and over the untreated control treatment. Also, the stevia plantlets derived from shoot tip treated with the lower concentration (10 ~MII) of jasmonic acid were tolerant up to 20 % salinity level and were able to continue their growth under glasshouse conditions till maturity and stevia yield production. The data also revealed that tolerance which was more pronounced as a result of phenylalanine amonialyase (PAL) activity the lower rate of jasmonic acid and was associated with high accumulation of much more quantities inorganic osmotica,i.e. N, P, K, Mg and Ca as well as lowest quantities of Na, in addition to considerable accumulation of organic protective osmolytes (sucrose, proline, amino acids and total soluble phenols), stevioside (%), photosynthetic pigments (carotenoids and chlorophylls) and endogenous hormones (1M. G~ and ABA) , in addition to the lowest invertase activity and higher phenylalanine in the stressed leaves in favor of accumulation more non-reducing sugars in the stevia grown in vitro and ex vitro . Such accumulation increased as the salinity level was increased. Such behevior seems to induce more ability for stevia plants to continue their growth till rnaturky and production of stevia yield even under 20 % salinity level.
The obtained data suggested the possibility of successful application of the jasmonic acid to improve salinity tolerance of economic crops such as stevia.