Dormancy-break and germination in seeds of Prunus campanulata (Rosaceae): Role of covering layers and changes in concentration of abscisic acid and gibberellin-- Effect of GAs and ABA

Intact seeds (seed + endocarp) from freshly harvested fruits of Prunus campanulata were dormant and required 4~6 weeks of warm followed by 8 weeks of cold stratification for maximum germination percentage. Removing both endocarp and seed coat, however, promoted germination in a high percentage of nonstratified seeds. Treatment of intact nonstratified seeds with gibberellic acid (GA3) was only partially effective in breaking dormancy. However, GA3 promoted germination of nonstratified seeds in which the endocarp (but not the seed coat) had been removed. Order of ABA concentration in fresh seeds was endocarp > seed coat > embryo, and its concentration in endocarp plus seed coat was about 6.2-fold higher than that in the embryo. Total ABA contents of seeds subjected to warm and/or cold moist stratification were reduced 6~12-fold. A higher concentration of GA4 was detected in embryos of nondormant than in those of dormant seeds. Fluridone, an ABA biosynthesis inhibitor, was efficient in breaking dormancy of Prunus seeds. Paclobutrazol, a GA biosynthesis inhibitor, completely inhibited seed germination, and the inhibitory effect could be partially reversed by GA4 but not by GA3. Thus, dormancy in P. campanulata seeds is imposed by the covering layers. Dormancy-break is accompanied by a decrease in ABA in covering layers and embryo and germination by an increase of GA4 in embryo.