Regulation of endogenous gibberellins and abscisic acid levels during different seed collection periods in Panax ginseng

Abstract

Ginseng (Panax ginseng Meyer) is an important oriental plant that has been used for medicinal purposes for centuries. Propagation of ginseng is frequently problematic due to its prolonged seed germination time. In this study tested the seasonal regulation of endogenous hormones (GAs and ABA) and hormone treatments in order to reduce the duration of the seed germination period. The embryo growth ratio increased from 10.2 to 33.7% between July 30, 2009 to October 27, 2009 and abruptly increased to 71.6% of the that. The seed germination rate assessed for different seed sizes revealed that approximately 60.2%–63.0% of the seeds had germinated by April 20, 2010; however, no significant differences in germination rate were observed among the different seed sizes. Analysis of GA showed that endogenous GAs were synthesized in the ginseng seeds through a non-13-hydroxylation pathway and the early 13-hydroxylation pathway. The GA contents were significantly increased from December 2009 to February 2010, while endogenous ABA contents were significantly reduced. However, the GA contents from August 2009 to December 2009 were lower than or comparable to the ABA contents, which were significantly increased. Thus, the total concentration of GAs and ABA during different seed growth stages suggests antagonism between these hormones. Similarly, the embryo growth ratio during the seed collection period revealed a similar trend in which the total GA and ABA contents were inversely related.