Propagation of Ornamental Plants
9(3): 135-142, 2009
REMOVAL OF DISTAL PART OF COTYLEDONS OR SOAKING IN BAP OVERCOMES EMBRYONIC DORMANCY IN SOUR CHERRY
Martin Jensen* and Kell Kristiansen
Department of Horticulture, Faculty of Agricultural Sciences, Aarhus University, Kirstinebjergvej 10, DK-5792 Aarslev, Denmark, *Fax: +45 89993496,
Dormant seeds of sour cherries (Prunus cerasus) normally require warm stratification for 2 weeks followed by cold stratification for 15-18 weeks to germinate. Seed treatments that reduce time to germination and increase germination percentages are important in breeding programmes and different experimental approaches to speed up germination were therefore investigated in this study. Removal of endocarps from dry or moist seeds resulted in high germination percentages after 2-4 months chilling and normal seedling growth. Dormant seeds with testa did not germinate at all at 20°C. Up to half of dormant excised embryos germinated at 20°C, but these showed abnormal seedling growth. Removal of the distal two-thirds of the cotyledons from dormant embryos gave 50 to 60% germination after two weeks at 20°C and seedlings grew normally. Excised dormant embryos soaked in 10 or 200 mg l-1 BAP for 30 min gave 70-80% germination at 20°C and seedlings grew normally, except for more lateral branches than in seedlings from chilled seeds. Soaking seeds with testa in the same concentrations of BAP for 24 h only improved germination slightly. The study showed that both endocarp, testa and embryo contributed to seed dormancy in sour cherry and that embryonic dormancy was caused by inhibitors in the cotyledons. Removal of part of the cotyledons or external application of BAP to excised embryos eliminated the block to germination and allowed normal growth of seedlings. High germination percentage and normal seedling growth may thus be achieved after only few weeks compared to traditional stratification and germination after 4-6 months.
Key words: correlative inhibition, cotyledons, cytokinin, embryonic dormancy, Prunus cerasus