Effects of temperature on seed germination characteristics of eight wild Poa germplasm

In order to provide the foundation for the introduction, domestication and utilization of wild Poa, six constant temperature treatments and two variable temperature treatments were employed to investigate the optimum temperature range on seed germination of eight wild Poa varieties. The results showed that the germination rate, germination potential, germination index, seeding length, root length and fresh weight of these varieties first increased then decreased with increasing temperature at constant temperature range of 10-35 ℃. The maximum germination rate occurred between 20-30 ℃ for the constant temperature treatment, the initial germination time was 4-5 days, the minimum occurred at 10 ℃ with the initial germination time between 11-14 days, which was 6-10 days later than the maximum germination rate. The germination rate, germination potential, germination index were taken as the primary parameters for optimal germination temperature selection, with reference of frond and root length, and fresh weight, the optimal germination temperatures of P.poophaqorum, P.pratensis and P.micrandra were 20 ℃ at constant temperature treatment, while those of P.pratensis(Xinglongshan), P.pratensis(Sunnan), P.pratensis(Weiyuan), P.pratensis(Tianzhu) and P.sphodylodes were 25 ℃ at constant temperature treatment. For most of the tested seeds, higher constant temperature favored the growth of frond, while lower (20 ℃) constant temperature or variable temperature favored the growth of root. Parameters at 5/20 ℃ and 10/25 ℃ variable temperature treatments were lower than their counterparts at 20 ℃ and 25 ℃ constant treatments.