Germination characteristics of three key species and their implications for vegetation restoration in northern China

Seed germination is a complex physiological process that can affect species establishment as well as vegetation restoration and dynamics; however, the germination characteristics of several key species used to combat desertification remain unclear. In light, temperature, and air humidity-controlled growth chambers, four different light treatments, five alternative temperature treatments, 11 levels of water potential, and five constant temperatures were set up to study the effects of light, temperature, and water stress on the completion of germination of Medicago sativa L, Astragalus adsurgens Pall., and Glycyrrhiza uralensis Fisch. The results showed that completion of germination of G. uralensis seeds occurred significantly less than that of M. sativa and A. adsurgens. Light intensity had no significant effect on the final germination percentage of M. sativa, A. adsurgens, and G. uralensis, but the germination rate under 100 and 400 mu mol.m(-2).s(-1) light was significantly greater than that under 25 mu mol.m(-2).s(-1). Temperature had no significant effect on the final germination percentage of these species' seeds, and the germination rate was greater at 15/25 degrees C and 20/30 degrees C. The germination rate decreased as the water potential decreased. The germination results indicate that late spring is a suitable sowing time for G. uralensis to obtain optimal levels of completion of germination.