Abstract

Soil salinity threatens initial stages of emergence and early seedling growth in cool season grasses, although it may be tolerant in its adult stages. Today, seed priming has been known as an effective technique for improving seed germination, seedling vigor, and emergence rate and seedling establishment under different environmental stresses. A pot experiment was conducted to evaluate osmopriming effects in ameliorating emergence rate (ER) and final emergence percentage (FEP), seedling growth, Na⁺ and K⁺ accumulated in shoot at early growth stages of two cool season grasses including tall wheat grass (Agropyron elongatum Host.) and bulbous barley (Hordeum bulbosum L.) when seeds were imbibed with CaCl₂, -1.5 MPa, and NaCl, -1 MPa for a duration of 2 and 5 days respectively, in response to seven salinity concentrations of NaCl (0, 50, 100, 150, 200, 250 and 300 mM) under greenhouse conditions. With increasing salinity levels, ER and FEP and seedling growth were significantly decreased in both grasses for primed and non-primed (control) seeds (p <0.01). But under severe salinity stress (300 mM) seed priming improved with regards to ER, FEP,accumulation of Na⁺, Na⁺:K⁺ ratio in shoot, root dry weight, shoot dry weight, root length and shoot length 62.6, 30.5, 44.7, 34.8, 42.5, 43.7, 31.7 and 20.9% when compared with non primed seeds, respectively. The relationships between salinity levels and ion accumulation showed that there was no significant correlation between Na⁺ accumulated in shoot and shoot dry weight in primed seeds (r= -0.15,P> 0.05) but for non-primed seeds increasing the accumulation of Na⁺ in shoot, led to significant decline (r= -0.62, P< 0.01) of shoot dry weight. The results suggest that seed priming could significantly improve the threshold value especially for FEPin both grasses under different levels of salinity. Also, it seems that seed priming could better improve root and shoot growth at early seedling growth stage perhaps by decreasing toxicity of Na⁺ concentration and adjusting Na⁺ and K⁺ ratio under saline conditions.

Key words: Early seedling growth, emergence rate, seed priming, salinity stress, cool-season grasses.