Role of Temperature and Gibberellic Acid in Stimulating Embryo Elongation and Radicle Emergence of Hepatica asiatica Nakai Seeds

Abstract

This research was performed to determine the temperature requirements for embryo growth and radicle emergence of Hepatica asiatica Nakai, a perennial herb native to Korea. Seed viability, embryo growth, and radicle emergence were monitored in seeds exposed to various temperatures (10, 15, <TEX>$20^{\circ}C$</TEX> and <TEX>$30{\rightarrow}15^{\circ}C$</TEX>). Laboratory experiments at various temperatures revealed that (1) embryo elongation occurred effectively between 10 and <TEX>$15^{\circ}C$</TEX>; (2) radicle emergence occurred only at <TEX>$15^{\circ}C$</TEX>; (3) a warm stratification (2-8 weeks at <TEX>$30^{\circ}C$</TEX>) was not required for embryo elongation and radicle emergence, and led to inhibition of radicle emergence; (4) application of gibberellic acid (<TEX>$GA_3$</TEX>) promoted embryo growth, but not radicle emergence. These results suggested that H. asiatica seeds have two separate mechanisms to overcome dormancy, either by <TEX>$GA_3$</TEX> (morphological dormancy) or temperature (physiological dormancy), and warm stratification is not involved in breaking radicle dormancy. These findings indicate that H. asiatica seeds have morphophysiological dormancy.