Changes in hormone content of Panax quinquefolium seeds during stratification

Abstract

The changes in hormone contents of Panax quinquefolium seeds during the after-ripening period under controlled stratification conditions were investigated. The seeds were stratified in sequence at 18-20°C for 80 d, at 8-13°C for 54 d and at 0-5°C for 88 d. The water content of the stratified medium (sand) was kept at about 10%. Gibberellin (GA 3) and indole-3-acetic acid (IAA) contents in the endosperm were very low at the beginning of stratification, then increased slowly to reach a small peak on day 164 and day 144, respectively, and finally both increased remarkably by day 198. The changes in the GA 3 and IAA contents in the embryo were similar to those in the endosperm. Zeatin might be responsible for cell division of the embryo of the seeds. The changing pattern of zeatin content in both the embryo and the endosperm was low-high-low, which corresponded to the changing pattern of the embryo growth rate. Abscisic acid (ABA) concentrations in both the embryo and the endosperm remained high before chilling (0-5°C), and dropped to very low values at the end of stratification. The drop in ABA contents might be due to the effect of low temperature during stratification.