実生法によるチューリップの育種学的研究(I-2) : 一年生実生の生育

When tulips have been grown by means of seedling culture, it ofen appears to be difficult to keep them growing. Therefore we have carried out research on the possibilities of influencing grow th, for it is of the utmost important to keep as many of the plants alive as possible, and to make them develop as soon as possible into healthy, flowering plants. In addition it may be possible to shorten the "juvenile phase" of the seedlings so that the plants come into flowering eariler. Then experiments on the influence of temperature were started by the present writer in 1954.
Our experiments, carried out in the field of our institute, with seedlings of tulips, raised from the seeds derived from the cross (i. e, intraspecific hybridization), have shown that the optimum temperature of growth and development may be in about 15℃ in the yearly cycle, namely the growth of subterranean stem (i. e. dropper stalk) had need of about 10-20 days long after germinations and the formation of bulb set out at 25days.
However, the growth of stalk under the condition of temperature below 10℃ had need of about 70 days long and at 70-105 days after germinations the formation of bulb set out. And under the abnormal higer temperature (i. e.above 25℃) the growth of stalk had been quickened and the formation of bulb set out at 10-20 days.
The survival rate of seedlings were highest under the optimum temperature, and brought low under the higher and lower temperature. The mortality under the higher temperature was high at the beginning of the growth and under the lower temperature decreased slowly in the term of growth.
Furthermore the 2nd part towards this study was a study of important commercial varieties grown in Japan. This led to : (a) the classification of the pattern appeared in the base of petals that there have been four categories, (b) the colour specification of tulip flowers that there have been six categories, (c) the investigations on the morphological distributions of pigments in tulip flowers and the analysis of pigments by the paper chromatography. These results so far obtained will be published in detail in detail in later issues of this periodical.