The effects of osmotic potential on germination and seedling growth in several populations of Elymus hispidus and Elymus pertenuis species

The genus of Elymus is of important grasses for forage production and soil and water conservation in Iran's rangelands. It has high preference value for livestock grazing because of the high production and high acceptability. Important species of this genus show different tolerances to drought. In order to determine the reactions of 14 accessions of Elymus hispidus and Elymus pertenuis to drought stress, a factorial experiment was conducted using completely randomized design with three replications in a standard germination test in 2008, Shiraz, Iran. Polyethylene glycol 6000 was used at 4 levels (0, -8/0, -9/0- and -1 MPa) as different osmotic potentials. Data were collected and analyzed for germination percentage, speed of germination, root length, shoot length, seedling length, root / shoot length ratio, seedling weight and seed vigor index. The results showed significant differences among accessions, drought effects and interaction effects of accessions* drought for all the traits. However, there were no significant differences between means of two species for all traits except seedling weight. In both species, all traits except root / shoot length ratio were decreased by increasing osmotic potential. In contrast, means of root / shoot length ratio was increased by drought stress. The effect of drought stress was higher on shoot length than those for root length, indicating that the sensitivity to drought stress of shoot length was more than root length. The results showed that some accessions within E. hispidus species as (Yasoj, Eghlid and Brojen) showed the maximum drought resistance in most of the seedling attributes. According to the results of Probit analysis, LD50 were estimated as -0.72 and -0.81 MP for E. hispidus and E. pertenuis, respectively.