Dormancy-break and germination in seeds of<i>Prunus campanulata</i>(Rosaceae): role of covering layers and changes in concentration of abscisic acid and gibberellins

<jats:title>Abstract</jats:title><jats:p>Intact seeds (seed+endocarp) from freshly harvested fruits of<jats:italic>Prunus campanulata</jats:italic>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 non-stratified seeds. Treatment of intact, non-stratified seeds with gibberellic acid (GA<jats:sub>3</jats:sub>) was only partially effective in breaking dormancy. However, GA<jats:sub>3</jats:sub>promoted germination of non-stratified seeds in which the endocarp (but not the seed coat) had been removed. The order of abscisic acid (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- to 12-fold. A higher concentration of GA<jats:sub>4</jats:sub>was detected in embryos of non-dormant than in those of dormant seeds. Fluridone, a carotenoid biosynthesis inhibitor, was efficient in breaking dormancy of<jats:italic>Prunus</jats:italic>seeds. Paclobutrazol, a GA biosynthesis inhibitor, completely inhibited seed germination, and the inhibitory effect could be partially reversed by GA<jats:sub>4</jats:sub>, but not by GA<jats:sub>3</jats:sub>. Thus, dormancy in<jats:italic>P. campanulata</jats:italic>seeds is imposed by the covering layers. Dormancy break is accompanied by a decrease in ABA content of the covering layers and germination by an increase of embryonic GA<jats:sub>4</jats:sub>content.</jats:p>