Germination Characteristics of Two Species of Polygonum in Relation to Their Altitudinal Distribution on Mt. Fuji, Japan

Abstract

The timing of seedling emergence crucially affects the fate of seedlings. Germination characteristics are therefore an important factor determining plant distribution. The aim of this study is to examine whether two species of Polygonum show different germination characteristics in relation to their altitudinal distributions (P. cuspidatum: lowland to alpine; P. weyrichii var. alpinum: mainly alpine and with a higher upper altitudinal limit than P. cuspidatum). The seeds of both species freshly collected in autumn required high temperature (350C) for germination. After winter, seeds of both species showed high germinability over a wide temperature range and the optimum temperature shifted to 20 to 250C. Response to storage differed between the two species. All the storage conditions examined (moist chilling, dry chilling and dry warm) were effective in breaking seed dormancy of P. cuspidatum, but seed dormancy of P. weyrichii var. alpinum was broken only by moist chilling. The germination at a low temperature (50C) after the winter was significantly higher in P. weyrichii var. alpinum than in P. cuspidatum. In contrast to these interspecific differences, none of our results indicated intraspecific differences with altitude in P. cuspidatum.