摘要
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 GA_3. 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(T_b) and thermal times for 50% germination(θ_(50)) 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 Tbvalues were 1 and 0.9℃, respectively, in two Rh. nobile populations; 4 and 4.1℃,respectively, in two Rh. alexandrae populations; θ_(50)(thermal time) were 100 and 125℃d, respectively in two Rh. nobile populations;
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 alexandme） 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 con- stant 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 （ther
基金
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.
the Young Academic and Technical Leader Raising Foundation of Yunnan Province to B. S.
