The temperature and length for the release of primary and induction of secondary physiological dormancy in Korean pine (
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The temperature and length for the release of primary and induction of secondary physiological dormancy in Korean pine (Pinus koraiensis Sieb. et Zucc.) seeds Y. Song1,3 · J. J. Zhu1,2 · Q. L. Yan1,2 Received: 21 July 2018 / Accepted: 19 September 2019 © Springer Nature B.V. 2019
Abstract Primary physiological dormancy and secondary physiological dormancy of Korean pine seeds restrict the regeneration of broad-leaved Korean pine (Pinus koraiensis) mixed forest. Dry and imbibed seeds were stratified at 1 °C and 5 °C for 1, 2, 4 and 6 months. Germination percentage, mean germination time (MGT) and germination rate index (GRI) were measured to determine the optimal low temperature and its duration for the release of primary physiological dormancy. Once primary physiological dormancy was released through cold stratification, seeds were stored in an environment in which the temperature progressively increased from 5 to 25 °C. After one month of storage at each storage temperature, the germination percentage, MGT and GRI were measured to determine the threshold temperature for the induction of secondary physiological dormancy. Both dry and imbibed seeds not only exhibited a high germination percentage (approximately 80%) but also germinated rapidly (MGT and GRI were 17 days and 2.36, respectively) after 6 months of storage at either 1 °C or 5 °C. The germination percentage of cold stratified seeds gradually decreased from 78% (5 °C) to 72% (10 °C), 55% (15 °C), 10% (20 °C) and 8% (25 °C). The results of this study suggest that stratifying seeds at 1 °C or 5 °C for 6 months releases primary physiological dormancy. The induction of secondary physiological dormancy occurs at temperatures above 15 °C. Keywords Korean pine · Primary physiological dormancy · Secondary physiological dormancy · Threshold temperature
* J. J. Zhu [email protected] 1
Qingyuan Forest CERN, Chinese Academy of Sciences, Shenyang 110016, China
2
CAS Key Laboratory of Forest Ecology and Management, Institute of Applied Ecology, Shenyang 110016, China
3
University of Chinese Academy of Sciences, Beijing 100049, China
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New Forests
Introduction The broad-leaved Korean pine (Pinus koraiensis) mixed forest (BKPF) was once the dominant forest type from Northeast China to the Far East region of Russia (Ishikawa et al. 1999). However, large-scale industrial deforestation led to a major reduction in the distribution of BKPF (Zhu et al. 2007). Korean pine is the dominant tree species in BKPF. Korean pine seeds have morphophysiological dormancy (MPD) at dispersal (Qi et al. 1993). In seeds with MPD, the embryos are not only underdeveloped or undifferentiated but also exhibit primary physiological dormancy (Baskin and Baskin 2004). Studies have previously shown that after fresh Korean pine seeds were buried between litter-fall and soil for 6 months (from the first late-autumn to the first early-spring season after seed dispersal), the embryo-length to megagametophyte-length was only approximately 0.64, but more than 80%
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