Breaking dormancy in freshly matured seeds of Elymus sibiricus, an important forage grass in the Tibetan Plateau.

Elymus sibiricus L. is an important forage grass widely distributed in Asia and is usually a dominant species on Tibetan Plateau alpine grasslands. Here, we used the seed development indices of 1000 seed weight, seed moisture content, and seed viability to compare the seed characteristics at 10, 20, 30, 40, 50, and 60 days after anthesis (DAA) in five populations of E. sibiricus growing in Gannan, China. Additionally, seeds collected at 60 DAA were air-dried for one month, and the primary germination percentage (GP) was determined in the laboratory. Treatment of seeds with 0.2% KNO3, 100 mg/L cytokinin, and 500 mg/L GA3 were tested for their effects on dormancy. A primary GP of 16% was found after 12 d of 15/25°C incubation, with no differences among the five populations. The 1000 seed weight and seed viability steadily increased and moisture content continuously fell with DAA. The optimal harvest time for E. sibiricus in an alpine pasture was 50 DAA. No effect on dormancy was found after treating seeds with 0.2% KNO3 or 100 mg/L cytokinin; however, a low concentration of GA3 induced a prompt and synchronized germination. Freshly matured E. sibiricus seeds were classified to be in non-deep physiologically dormant. Treatment of seeds with GA3 before sowing enhanced the emergence speed and seedling uniformity in E. sibiricus.