Changes in abscisic acid and gibberellin levels during stratification in Panax ginseng roots

The present study was carried out to get the basic information for clarifying physiological mechanism of breaking dormancy and sprouting in Panax ginseng roots. Changes in Abscisic acid (ABA) content and Gibberellin (GA) activity were investigated in one-year-old root during stratification at 4deg C, 15deg C, and 15deg C after 60 day-treatment at 4deg C. Sprouting rate at 15deg C was 35% in 30 days storage at 4deg C and 100 % in longer than 60 days, but there was no sprout in both the constant treatment at 4deg C or 15deg C regardless of the treatment period. The longer the period of low temperature treatment, number of days to the first and 50 % sprouting was shortened, and number of days to 50 % from first sprouting was also shortened. ABA content in the upper part of root (contained bud) was gradually increased at both 4deg C and 15deg C as the treatment period was extended, and the degree of increase was higher at 15deg C. In the lower part, it showed a slight increase at 15deg C, while showed little change at 4deg C throughout the treatment period. In the 15deg C treatment after 60 days at 4deg C, it was greatly increased in the upper part, while rather slightly decreased in the lower part of root. GA activity in the upper part was gradually decreased at both 4deg C and 15deg C, and the degree of decrease was higher at 15deg C. In the lower part, it was similar tendency to those in the upper part. In the 15deg C treatment after 60 days at 4deg C, it was remarkably increased in both the upper and lower part. The increase was great in the low Rf region, while the decrease appeared relatively in the high Rf region compared to those of 60 day-treatment at 4deg C. The above results indicated that the breaking dormancy and sprouting of bud were closely associated with the degree of GA activities in response to temperature condition during stratification rather than the direct effect associated with the changes in ABA content