Increasing Seed Germination Efficiency of Tall Wheat Grass (Agropyron elongatum (Host.) P. Beauv) at Low Temperature and Drought Stress Conditions Using Urea Osmopriming

Seed priming is one of the most important techniques used to improve seed germination under biotic and abiotic stresses. For this purpose, germination and seedling growth characteristics of primed seeds of Tall wheat grass (Agropyron elongatum (Host.) P. Beauv) were evaluated under drought and low temperature condition. A factorial experiment was conducted on the basis of randomized completely block design with three factors with four replications. The experimental factors were priming with two levels including urea primed (using urea -4 bar at 10 °C for 36 h) and non-primed seeds; germination temperatures, including 3, 6, 9, 12, 15, 20 and 25 °C; and osmotic potential including zero (distilled water), -3, -6, -9, and -12 bars (applied by polyethylene glycol 6000). Increasing trend have been observed for all germination indices, except mean germination time, with increasing temperature from 3 to 25 °C and seeds revealed the greatest sensitivity to temperatures below 9 °C. However, this trend was reversed with increasing drought stress, the seeds sensitivity to drought stress started from the potential of -6 bar and reached to maximum in -12 bar. However, primed seeds compared to non-primed seeds have demonstrated better germination under both drought and low temperature stresses. The results of this study showed that the highest seedling vigor index and germination rates achieved in the temperature range of 20-25 °C and water potential of zero to -3 bar.