Comparison of Thermal and Hydrotime Requirements for Seed Germination of Seven Species From Cool and Warm Habitats.

Temperature and water potential are two important environmental factors influencing germination and subsequent seedling establishment. Seed germination requirements vary with species and with the environment in which the seeds are produced. species dominate large areas of the Eurasian zonal vegetation, but comparisons of germination requirements between species from different habitats is limited. We investigated the effects of temperature and water potential on seed germination of , , and from habitats with low temperatures and relatively abundant rainfall (cool habitats) and , , , and from habitats with relatively high temperatures and low amount of rainfall (warm habitats). Seeds of species from cool habitats had a higher base ( ), optimal ( ), and maximum ( ) temperature than those of species from warm habitats, except for the base temperature of . Response of six tested species to water potential differed among species but not between habitats. Median water potential for germination was lowest for , , and . There was a negative correlation between hydrotime constant ( ) and base water potential for 50% of the seeds of all species to germinate ( ). Germination time of seven species in response to temperature and water was well predicted by thermal time and hydrotime models. Results of the present study on germination of these seven species of may provide useful suggestions for grassland restoration in different habitats.