Plant Diversity ›› 2017, Vol. 39 ›› Issue (04): 180-186.DOI: 10.1016/j.pld.2017.05.009

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Seed dormancy and germination characteristics of two Rheum species in the Himalaya-Hengduan Mountains

Deli Penga,b, Zhe Chena,d, Xiaojian Huc, Zhimin Lib, Bo Songa, Hang Suna   

  1. a Key Laboratory for Plant Diversity and Biogeography of East Asia, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming 650201, Yunnan, China;
    b School of Life Science, Yunnan Normal University, Kunming 650500, Yunnan, China;
    c Germplasm Bank of Wild Species in Southwest China, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming 650201, Yunnan, China;
    d University of Chinese Academy of Sciences, Beijing 100049, China
  • Received:2017-03-04 Revised:2017-05-27 Online:2017-08-25 Published:2021-11-05
  • Contact: Bo Song, Hang Sun
  • Supported by:
    This study was supported by National Key Research and Development Program of China (2017YFC0505201), NSFC (grant 31670206 to Z.-M. L. and 31570228 to B. S.), major Program of NSFC (grant 31590823 to H. S.), the Orientation Training Programme for Postdoctoral Fellows from Yunnan Province to D.-L. P., and the Young Academic and Technical Leader Raising Foundation of Yunnan Province to B. S.

Abstract: Seed dormancy and germination characteristics are important factors determining plant reproductive success, and may be expected to have a major influence on plant distribution. In this study, we aimed to explore the characteristics of seed dormancy and germination in two endemic Rheum species (Rheum nobile and Rheum alexandrae) in the Himalaya-Hengduan Mountains. To determine the type of dormancy, fresh seeds of the two species (one population each) were incubated in light at 25/15 and 15/5℃, and then dry after-ripening (DAR) seeds were incubated on water agar substrate with or without GA3. To determine the effect of temperature and light on germination, DAR seeds of the two species (two populations each) were incubated both in the light and in the dark at several temperatures, including constant and alternating temperatures. Base temperature (Tb) and thermal times for 50% germination (θ50) were calculated. DAR released physiological dormancy (PD), increasing final germination at 15/5℃ and widening the range of germination temperatures from higher to lower, indicative of type 2 non-deep PD for the two Rheum species. Light had no significant effect on germination of seeds from the two species (two populations each). Seeds of the two species germinated significantly better (>80%) at medium temperatures (10-25℃) than at extreme low (5℃) or high (35℃) temperatures. Alternating temperatures (25/15 and 15/5℃) did not significantly increase the final germination of the two species either in the light and in the dark, but it promoted seed germination more quickly than corresponding constant temperatures in the light in both Rh. alexandrae populations, especially at 15/5℃. Germination in response to temperature was well described by the thermal-time model at suboptimal temperatures. The estimated Tb values were 1 and 0.9℃, respectively, in two Rh. nobile populations; 4 and 4.1℃, respectively, in two Rh. alexandrae populations; θ50 (thermal time) were 100 and 125 Cd, respectively in two Rh. nobile populations; 76.92 and 83.33 Cd, respectively in two Rh. alexandrae populations. The dormancy type, and germination responses to temperature and light condition does not explain why the two Rheum species are distributed in contrasting habitats. However, these findings reflect an advantageous germination strategy of these two Rheum species to adapt to the same alpine environments.

Key words: Germination, Light, Rheum alexandrae, Rheum nobile, Dormancy, Temperature