Morphophysiological dormancy and germination ecology in diaspores of the subtropical palmPhoenix canariensis

The timing of germination is a crucial event in a plant’s life cycle. Seed dormancy and germination mechanisms are important factors regulating seedling emergence. Since detailed experimental evidence of the germination pattern of Phoenix canariensis Chabaud colonizing sub-tropical climates is scarce, we investigated seed dormancy and germination ecology of P. canariensis. We found that the embryo is underdeveloped at the time of dispersal and doubles in size before the cotyledonary petiole (CP) protrudes through the operculum. The primary root and plumule emerge from the elongated CP outside the seed. In light/dark cycles of 30/25 °C, the CP emerged from 8% of the diaspores within 30 days and from 76% within 14 weeks. Thus, 8% of the diaspores have morphological dormancy and the others have morphophysiological dormancy. Removal of the pericarp and operculum resulted in 100% germination within five days in a light/dark cycle of 30/25 °C. Cold and warm stratification as well as treatment with GA3significantly increased the germination speed but the final germination percentage was not significantly increased. Seed germination was synchronized in early summer when seed dormancy was released by cold stratification in the soil over winter. A remote-tubular germination type and intricate root system provide an ecological advantage to seedling establishment.