Dormancy and germination characteristics of the dimorphic seeds of Polygonum aviculare

Polygonum aviculare is an annual herb that can be planted as an excellent ground cover plant for garden and lawn greening. In this study, we observed and compared the morphological characteristics of P. aviculare seeds, and conducted seed germination experiments under five different thermoperiods of 5 ℃/15 ℃, 10 ℃/20 ℃, 15 ℃/25 ℃, 20 ℃/30 ℃, and 25 ℃/35 ℃ (dark12 h/light 12 h). The following results were obtained. 1) P. aviculare produced two types of fruits on the same plant that differ markedly in shape, size, and color. One is a shiny tawny colored seed of narrow ovate shape, with a length of 3.15 mm and thousand-grain weight of 1.77 g, whereas the other is a dull dark brown color, ovate in shape, with a length of 1.91 mm and a thousand-grain weight of 1.33 g. 2) Under each of the five temperature regimes, the percentage germination of the tawny seeds was greater than 80%, which is high. Contrastingly, the germination rate of the dark brown seeds was low, with a final percentage germination of 50%. These latter seeds are thus considered to show a dormancy phenomenon. 3) The germination rate of dark brown seeds could, however, be significantly increased by scarification of the covering layers (pericarp and seed coat) and cold stratification, thereby indicating that these seeds were not in a state of deep physiological dormancy. Further research on seed polymorphism and germination behavior in P. aviculare may provide basic data for the development and utilization of this ground cover plant resource.