GERMINATION RESPONSES OF RUBUS-PALMATUS VAR COPTOPHYLLUS AND RUBUS-PARVIFOLIUS SEEDS WITH DIFFERENT BURIAL DURATIONS TO A VARIABLE LIGHT AND TEMPERATURE REGIME

To clarify the adaptive significance of seed dormancy, the effects of burial duration were examined for two deciduous Rubus species: Rubus p almatus var. coptophyllus and Rubus parvifolius, which are found mainl y in relatively stable, shaded sites and disturbed sites, respectively . In early summer, newly ripened seeds were buried under litter on the soil surface in a pine forest, and germination tests were carried out for the seeds retrieved from the soil litter after 0 (nor buried), 1, 2, 3, 5 and 8 or 9 months of burial. In general, the germination perc entages increased and light requirements for germination decreased wit h increased burial duration. The percentage of seeds germinated with a lternating temperatures in darkness also increased with increasing bur ial duration for both species. After 8 or 9 months of burial (correspo nding to the next germination season in the field), the percentage of non-dormant seeds (including germination under alternating temperature s in the dark) was about 80% and 40% for R. palmatus var. coptophyllus and R. parvifolius, respectively. These seed dormancy traits of the t wo Rubus species may explain the differences in germination strategy i n their habitats: R. palmatus var. coptophyllus seems to have adapted to the seasonal occurrence of favorable growing conditions after the d ormancy breakage, while R. parvifolius seems to have adapted to favora ble conditions created by temporally unpredictable disturbances.