The base temperature and the thermal time requirement for seed germination of 10 grass species on the eastern QinghaiTibet plateau

Abstract: Temperature is an important environmental factor influencing seed germination. In this study, we used the thermal time model to analyze the thermal time requirement and base temperature for germination of 10 grass species under five constant temperatures (5, 10, 15, 20, 25 ℃) on the eastern QinghaiTibet plateau. We found that the base temperatures ranged from 0 to 4 ℃，and thermal time ranged from 26.65 to 139.92 ℃d. The base temperature was lower and the thermal time was higher for germination compared with other researchers' findings, which adapted to their special lived temperature environment of the QinghaiTibet plateau. There was a significant negative correlation between altitude and base temperature for germination(P0.05), which reflected that the base temperatures of these seeds' germination were adapted to their specific temperature environment in this region. Two annual Bromus species had lower thermal time for seed germination than other 8 perennial species. Therefore, the annuals germinated earlier and occupied the priority of space resources and benefited from the community competition than the perennial species.