In: Phyton 54, Fasc. 2 (2014): S. 305-320 DOI: 10.12905/0380.phyton54(2)2014-0305

Key words: Robinia pseudoacacia, Fabaceae, invasive tree species, phenology, lignification of seed coat, physical dormancy.

Summary

Watanabe Y., Karaki T., Kondo T. & Koike T. 2014. Seed development of the black locust and physical dormancy in northern Japan. – Phyton (Horn, Austria) 54 (2): 305–320, with 4 figures.

To determine the traits of seed propagation of the black locust, an invasive woody legume, in northern Japan, we studied the development process of black locust seeds by phenological observation and by physiological and anatomical analyses. We collected seeds from two mother trees at several times between August and March in 2007–2009. From each tree, seeds were sampled over the same interval each year. Seeds began to form at the end of June. Internal tissue development of seeds started at the end of June, and was completed by early September. At that time, black locust seeds were able to germinate. Lignification of the seed coat progressed from early to late September as the moisture content fell abruptly, leading to the onset of physical dormancy from late September. The onset of physical dormancy of black locust varied from year to year. In 2007, regardless of the complete lignification of the seed coat, seeds were able to imbibe water and germinate in late September. Consequently, these seeds were not dormant. In 2007 most seeds were in a state of physical dormancy between late September and the end of December, but some seeds remained non-dormant. These two types of seeds, non-dormant and having physical dormancy, give rise to a wide period of germination, greatly increasing the opportunities for seedling establishment.