Germination characteristics of Artemisia ordosica (Asteraceae) in relation to ecological restoration in northern China

Artemisia ordosica Krasch. (Asteraceae) is the dominant psammophytic shrub species on the Ordos Plateau of northern China and is used for revegetation of semi-arid areas. Experiments were conducted to determine the effects of light intensity, constant temperature, alternating temperatures, and water potential on germination to determine why air-dispersed achenes fail to germinate well in the field. Achenes germinated within a wide alternating temperature window, except under the 5:15°C (night:day) temperature regime in darkness. Final percent germination (FPG) was higher in darkness than in light at alternating temperature regimes, except under the 20:30°C (night:day) temperature regime. Achenes subjected to a range of constant temperatures in the dark had high FPG over 76.8% except at 30°C (8%). Photosynthetic photon flux densities (PPFD) of 100 and 400 μmol·m-2· -1 significantly lowered FPG under a 10:20°C (night:day) regime, while at 0-25 μmol·m-2°s-1 PPFD, the FPG was over 92%. Few achenes germinated at -1.4 MPa. The most suitable temperature for germination of achenes placed under water stress was 20°C. The best timing for air dispersal is mid-May, so seeds would become covered with sand at a time when temperature and soil moisture conditions were optimal for germination. © 2005 NRC.