Seed Germination in Cercidiphyllum japonicum and Cercidiphyllum magnificum Varies with Temperature

Abstract

To quantify the germination rate of Cercidiphyllum japonicum, which inhabits montane zones and Cercidiphyllum magnificum, which inhabits subalpine zones, we conducted germination tests at 10, 15, 20, 25, and 30 °C for 45 days. The germination rate of C. japonicum varied from 12.7％ at 10 °C to 31.7％ at 20 °C, and that of C. magnificum varied from 3.7％ at 15 °C to 22.7％ at 25 °C. The number of germinated C. japonicum seeds was significantly greater at 20, 25, and 30 °C than at 10 °C, and the number of germinated C. magnificum seeds was greater at 20 and 25 °C than at 10 and 15 °C. More C. japonicum seeds germinated at all temperatures relative to C. magnificum, and the mean time to germination was shorter in C. japonicum relative to C. magnificum at 10, 15, and 30 °C. We thus concluded that C. japonicum possesses high germination rates across the range of tested temperatures and that C. magnificum has poorer tolerance to low temperatures during germination and a reduced germination rate. We also observed C. magnificum takes longer to germinate than C. japonicum.