Comparing the relationship between seed germination and temperature for Stipa species on the Tibetan Plateau

Abstract

Alpine steppe grasslands dominated by Stipa species (Poaceae) on the Tibetan Plateau are important model ecosystems. Here, we present data on seed germination of three typical Stipa species (Stipa purpurea Griseb., Stipa glareosa P.A.Smirn., and Stipa capillacea Keng) from the northern core region of the Tibetan Plateau. We carried out laboratory investigations of germination behavior under both constant and alternating temperatures. Germination varied significantly with temperature. Under constant temperature, we found that temperature and species, but not their interaction, had significant effects on seed germination. Under alternating temperatures, species had a significant effect on seed germination, whereas the effects of alternating temperature and the interaction between species and alternating temperature were not significant. In addition, light and the interaction of light and species had no significant effect on seed germination; however, species had a significant effect, implying that Stipa species on the Tibetan Plateau are not inhibited by light. Base temperatures of S. glareosa, S. purpurea, and S. capillacea were 1.0 °C, 0.1 °C, and –1.4 °C, respectively, with corresponding thermal times at suboptimal temperatures of 233 °C-day, 154 °C-day, and 263.2 °C-day. Our results suggest that Stipa seed germination characteristics are adaptions to a harsh environment and are species-specific.