Previous studies suggest that when using natural regeneration of Korean pine (Pinus koraiensis Sieb. et Zucc.) many seeds do not germinate until the second Spring after dispersal and hence are subject to significant predation pressures. This could be an important factor affecting the restoration of Mixed-broadleaved Korean pine forests in northeast China. This study examined changes of dormancy status under laboratory and field conditions as well as physiological mechanisms involving abscisic acid (ABA), gibberellin acids (GA(1+3), GA(4+7)) and the storage reserves of seeds. Our results suggest that seeds of Korean pine have primary dormancy that can be classified as morphophysiological dormancy, i.e. when dispersed they have an underdeveloped embryo with a physiological component of dormancy. A proportion of seeds germinate in the first year after dispersal as the winter chill has broken the physiological dormancy but only when the embryo has had time to elongate in April-June. The remaining seeds germinate in the second Spring after dispersal when embryos are fully developed and the physiological dormancy imposed in the Summer after dispersal has been broken by winter chilling. Thus the seed strategy of Korean pine attempts to reduce risks by providing opportunities for germination in 2 years following dispersal. |
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