Seed Germination and Storage Behavior of Taiwan Incense-cedar (Calocedrus macrolepis Kurz var. formosana (Florin) Cheng L. K. Fu)

摘要

Taiwan incense-cedar (Calocedrus macrolepis var. formosana) is not only an endemic variety but also a valuable and vulnerable conifer native to Taiwan. The purpose of this study was to understand the germination characteristics of seeds of C. macrolepis var. formosana and determine its seed storage behavior. Optimal seed storage conditions and methods are also given for ex situ conservation. The respective germination percentages of 3 seedlots under fluctuating temperatures of 30/20℃ with 8 h of light for 8 wk were 68.0, 95.3, and 89.3%, and the mean germination times were 11.9, 10.9, and 10.9 d, respectively. All viable seeds of these 3 seedlots had completely germinated within 3 wk. Thus, seeds of C. macrolepis var. formosana exhibited no dormancy. In seedlot 1, with moisture contents (MCs) (on a fresh-weight basis) dried to 5.0~14.4%, the germination percentages of seeds with 2 yr of storage at -20℃ were 53.4~74.4%. In seedlot 2, when the MCs were controlled to 5.7~11.2%, germination rates after 2 yr of storage at -20℃ were 92.5~95.4%. In addition, germination rates of seedlot 3 dried to 8.2 and 11.3% MCs still remained as high as 80.8~89.8% after 3 yr of storage at -20 and -196 ℃. These results of maintaining good seed viability show that C. macrolepis var. formosana seeds seem to exhibit orthodox storage behavior. However, the germination percentage of seedlot 3 seeds decreased to about one-third of the original value when seeds were dried to about a 5% MC. Obviously, this characteristic of quickly losing seed viability shows the difference from small conifer tree seeds with orthodox storage behavior. Moreover, optimal MCs for maintaining seed viability were 8~11% rather than 5% when seeds from these 3 seedlots were stored at -196~15℃. Thus, we consider that seeds of C. macrolepis var. formosana are very likely to show intermediate seed storage behavior with some desiccation and sub-zero temperature tolerance, which differs from typical orthodox seeds. Sub-zero temperature storage was actually helpful for preserve Taiwan incense-cedar seeds. We recommend that fresh mature seeds of C. macrolepis var. formosana be quickly dried to 8~11% MCs and then hermetically sealed immediately before storage at -20℃. The reason why it is hard to preserve seeds of C. macrolepis var. formosana for long-term ex situ conservation is its probable intermediate storage behavior with a limited lifespan. Thus, we suggest that stored seeds of C. macrolepis var. formosana be renewed about every 10~15 yr.