Studies on the seed germination and dormancy of Ilex rotunda, Castanopsis fargesii, Melia azedarach and Helicia rengetiensis from central Taiwan

Many mature seeds of woody plants in Taiwan exhibit dormancy, which delays germination and effects successful establishment of seedlings. Therefore, promoting seed germination is a critical task of nursery management. The purpose of this study was to investigate seed germination and dormancy of four broad-leaved dominant trees from central Taiwan: Ilex rotunda, Castanopsis fargesii, Melia azedarach and Helicia rengetiensis. Our results showed that seeds of I. rotunda exhibited non-deep morphophysiological dormancy, beginning to germinate after 8 weeks of incubation. Depending on incubation temperatures, 40-50% of the seeds had germinated by 24 weeks. Seeds of C. fargesii exhibited non-deep physiological dormancy, with 10% germination after 4 weeks of sowing and 68% after 8 weeks. Although pretreatment of moist cold stratification shortened the germination time of C. fargesii seeds, we found that moist cold stratification and incubation together delayed seed germination compared to simple incubation. Thus, pretreatment with moist cold stratification is unnecessary for C. fargesii seeds. Seeds of M. azedarach exhibited physical dormancy and required pretreatment with hot water at 80°C followed by allowing them to cool in the water, or presoaking in room temperature water for 24 hours or longer to promote germination. Seeds of H. rengetiensis exhibited partial non-deep physiological dormancy and could be presoaked in room temperature water for 12-24 hours before sowing. In conclusion, dormant seeds require appropriate dormancy breaking treatment before sowing to accelerate germination and produce uniform seedlings. © 2024 Taiwan Forestry Research Institute. All rights reserved.