Changes of Phenolic Compounds and Abscisic Acid in Liriope spicata Seeds according to Cold Stratification and Seed Harvesting Date and Their Relationships to Germination

This study was conducted to investigate the changes in total phenolic compounds and abscisic acid (ABA) according to cold stratification and seed harvesting date, and to examine the relationship between germination and the two probable inhibitors in Liriope spicata (creeping lily-turf) seeds. Germination percentage increased in a stratification duration-dependent manner and further stratification beyond 30 days did not show significant difference. Although total phenolic compounds and ABA contents of stratified seeds ranged from 30 to 60 days after cold stratification were slightly reduced, those of the seeds ranged from 0 to 30 days after cold stratification markedly decreased in a duration-dependent manner. Especially, total phenolic compounds and ABA within the seeds greatly decreased during the first 30 days of cold stratification. Depulped L. spicata seeds collected on October 12 did not germinate at all until 40 days after sowing, while those on following harvesting dates ranged from October 22 to December 21 showed various germination percentages ranged from 11.5 to 93.2%. Maximum germination percentage (93%) was obtained from seeds harvested from November 22 and December 1. The lowest content of phenolic compounds within seeds were found on November 22, following December 1, December 11, November 12, sequentially. The increase and decrease pattern of ABA during seed development was very similar to those of phenolic compounds within seeds. In conclusion, enhancing germination by depulping and cold stratification could be attributed to the removal of phenolic compounds and ABA within the pulps and the seeds of L. spicata. In addition, reduction of phenolic compounds contents and ABA within seeds during seed development seemed to be positively correlated with their germination percentage according to seed harvesting dates.