Seed Storage Behavior of Sapium discolor Muell.-Arg.and Bischofia javanica Blume

The storage behavior and germination characteristics of seeds of Taiwan tallow tree (Sapium discolor) and Javanese bishopwood (Bischofia javanica) were investigated in the present study. The germination percentage of freshly collected mature seeds of S. discolor from Duona, Kaohsiung County in 1997 was 59% over 16 weeks under alternating temperatures of 30/20℃ with 8 h of light. With cold stratification of freshly collected seeds for 2 mo, the germination percentage reached as high as 85.3%. Therefore, about 30% of seeds showed deep dormancy. The mean germination time was reduced from 54 d for freshly collected mature seeds to 41 d after 1 mo of stratification. Seed germinability of S. discolor could be maintained at -20~15℃, for at least 24 mo at MCs (moisture contents) of between 1.8 and 7.9% (on a fresh-weight basis). These results confirm that S. discolor seeds exhibit orthodox seed storage behavior. The germination percentage of freshly collected mature seeds of B. javanica from Sansia, Taipei County in 1997 was 78% over 8 weeks under alternating temperatures of 30/20℃ with 8 h of light, and the mean germination times were between 10 and 18 d. Most freshly mature seeds survived when they were desiccated to 5.3~12.5% MCs; however, the viability of those seeds with 3.7~12.5% MCs dropped significantly at -20℃ after 24 mo of hermetic storage. The optimum seed moisture contents of B. javanica were 8, 5~13, and 5~8% for -20, 4, and 15℃ storage, respectively. The temperature effect on seed longevity revealed that the longevity of seeds stored at 4℃was better than those at -20 and 15℃. We estimated that the optimum seed storage conditions for B. javanica are provided by combining a temperature of 4℃ with about an 8% MC. These results confirm that B. javanica seeds exhibit intermediate storage behavior that is characterized as being tolerant to desiccation but sensitive to freezing temperatures.本研究针对台湾乌桕（Sapium discolor）与重阳木（Bischofia javanica）的种子贮藏特性及萌发特征开展了系统调查。1997年采自高雄县多纳乡的新鲜成熟台湾乌桕种子，在30/20℃变温、每日8小时光照条件下培养16周，萌发率为59%。对新鲜采收的种子进行2个月低温层积处理后，其萌发率最高可达85.3%，由此表明约30%的种子存在深度休眠。经1个月层积处理后，种子平均萌发时间从新鲜采收时的54天缩短至41天。台湾乌桕种子可在-20℃~15℃、以鲜重计含水量为1.8%~7.9%的条件下贮藏至少24个月，该结果证实台湾乌桕种子属于正常型贮藏种子（orthodox seed storage behavior）。 1997年采自台北县三芝乡的新鲜成熟重阳木种子，在30/20℃变温、每日8小时光照条件下培养8周，萌发率为78%，平均萌发时间介于10~18天。多数新鲜成熟种子经干燥至含水量5.3%~12.5%后仍可存活，但当含水量处于3.7%~12.5%区间的种子在-20℃密闭贮藏24个月后，活力显著下降。重阳木种子在-20℃、4℃、15℃下贮藏的最适含水量分别为8%、5%~13%与5%~8%。温度对种子寿命的影响显示，4℃贮藏条件下的种子寿命优于-20℃与15℃。据此推断，重阳木种子的最优贮藏条件为4℃搭配约8%的含水量。本研究结果证实，重阳木种子属于中间型贮藏种子，其特征为耐干燥但对低温敏感。