Seed dormancy and germination characteristics in relation to the regeneration of Acer pycnanthum, a vulnerable tree species in Japan

Abstract

Seed dormancy and germination characteristics of the vulnerable tree species Acer pycnanthum were investigated to understand its regeneration strategy. Seeds of A. pycnanthum mature 1 month after pollination and are dispersed in late spring. All dispersed seeds were in dormancy upon collection from which they were released by cold (5 °C) stratification over a period of at least 12 weeks. Germination percentages were higher under low temperature conditions (10–20 °C) and when the temperature was alternated in diurnal cycles. Light effects on germination were not observed. Seed viability was not lost even though seeds had experienced room temperature conditions (20–30 °C, 35–70 % humidity) after dispersal for 5–10 months. Seeds of A. pycnanthum can endure summer heat and survive until the following spring, allowing their seedlings to germinate promptly. In the case of light intensity-independent dormancy release, regeneration can occur under canopy conditions where shade-intolerant seedlings are at a disadvantage. To verify this conclusion, the shade tolerance of A. pycnanthum requires further investigation.