The effect of salt stress on germination and growth of Agropyron cristatum and Agropyron elongatum with iso- osmotic solutions of sodium chloride and Polyethylene glycol 6000

Salt and osmotic stresses are responsible for both inhibition or delayed seed germination and seedling establishment. Salts may affect seed germination by either restricting the supply of water (an osmotic effect) or causing injuries through involvement of their ions into the metabolic processes (ionic effect). The aim of the study was to determine the effect of salt and osmotic stresses on Agropyron cristatum and Agropyron elongatum seeds. In this respect, iso-osmotic solutions of sodium chloride (NaCl) and Polyethylene glycol 6000 (PEG 6000) under osmotic stress levels of (0, 4 and 8 bars) were applied to induce osmotic and ionic effects. The applied experimental design was completely randomized design with a three-factor factorial (2×2×3) arrangement in three replications and 50 seeds per replication. Germination percentage, germination rate, shoot length and vigor index showed significant reduction due to higher osmotic tensions on both Agropyron species. Only root length had no statistically significant difference between stress levels 0 and 4 bars. Iso-osmotic solutions of NaCl and PEG 6000 in A. cristatum did not show statistically significant difference, but in the case of A. elongatum significant differences were observed between these two iso- osmotic solutions. This study showed that PEG 6000 as an osmotic agent of salinity had more inhibition effect rather than ionic effect of Nacl. However, the toxicity of ionic effects was raised by increase of osmotic stress levels. This study showed that the tolerance of A. elongatum against salinity was more than A. cristatum species.