Temperature dependence of seedling establishment of a perennial, Dioscorea tokoro

The temperature dependence of seed germination and seedling growth was analyzed in Dioscorea tokoro, an East Asian summer-green perennial. Seeds were able to germinate fully only at 11deg-20degC. At around 17deg-20degC the first leaf petiole of the seedling elongated and quickly set the first leaf blade at a position enabling photosynthesis. At temperatures higher than 20degC petiole elongation was retarded, and seedlings formed a rhizome and established as a perennial. The rhizome size increased with temperature up to 29degC. Thus, during growth immediately after germination, temperature appears to be a key factor in determining whether the plant establishes as a perennial or grows rapidly without rhizome thickening.