The present paper examined the effects of light treatments on the seed germination of Pometia tomentosa—a canopy tree species in seasonal rain forest of Xishuangbanna. The results showed that the final germination percentage of P. tomentosa seed was high under both consecutive illumination and 14 h/10 h light-darkness cycle of all light intensities, and no significant difference was observed among treatments. Illumination reduced the coefficient of germination rate, but increased germination index and vigor index. The germination percentage increased with decreasing light intensity in shade house and the highest germination percentage (78.9% ) was achieved at 0.6% of natural sunlight (NS), and the lowest germination percentage (27.8%) was achieved at 100% of NS. The germination percentage at 100% of NS was significantly lower than those of shading treatments, although there were no significant differences among shading treatments. The coefficient of germination rate in shading treatment decreased with reducing light intensity, while germination index and vigor index exhibited a converse tendency. It is suggested that the germination of P . tomentosa seed in shading treatment can be affected by seed desiccation resulting from evaporation of soil water under high light intensity and by the death of“germinated seeds”which could not grow to match the criterion of germination. This implies that both avoiding the death of seed desiccation resulted from high temperature under high light intensity and improving the quality of seed germination and seedling survival by providing suitable light for them are emphasized in the protection of germplasm resources of P. tomentosa.
