Varietal Differences in the Photoperiodic Responses of Rush Plants (Juncus decipens Nakai)

Abstract

In order to clarify the varietal differences in photoperiodic responses of rush plants, tests were conducted from October 1964 to June of the next year. The results are summarized as follows: 1. The sods of clone of four rush varieties (Hirokei No. 373, Sazanami, Asanagi and Hirokei No. 369) were planted in pots on October 1, 1964 and grown outdoors. The plants were moved to each place under three different conditions (long day -natural temperature condition, natural day length -high temperature condition, and long day- high temperature condition) almost every month during the period from October 1964 to April of the next year, and the plants placed under the natural day length- natural temperature condition was tested. 2. Under the natural day length-natural temperature condition, four varieties flowered earlier in order of Hirokei No. 373, Sazanami, Asanagi and Hirokei No. 369, and it was observed that the earlier flowering varieties had a tendency to bear a larger number of inflorescences. As to the number of inflorescences, the same tendency was observed also in cases of plants grown under other conditions. 3. Under the long day-natural temperature condition, the flowering of four varieties was accelerted compared to that under the natural day length- natural temperature condition, in case where the treatments were begun from October or November. The degree of acceleration was higher in order of Hirokei No. 373 > Sazanami > Asanagi·Hirokei No. 369, that is to say, varietal differences in floral responses were observed in the acceleration by long day. 4. Under the long day- high temperature condition, the flowering of three varieties except Hirokei No. 369 was accelerated, even if the treatment might be started at whatever time. 5. Under the natural day length-high temperature condition, the flowering of Hirokei No. 373 was accelerated by the treatments in and after January. The flowering acceleration of Sazanami and Asanagi was observed by the treatments in and after February and March, respectively. From the facts stated above, it is inferred that the critical photoperiods of Hirokei No. 373, Sazanami, Asanagi and Hirokei No. 369 touch a level of about 10, 11, and 12 hours, respectively, i.e., varietal differences in critical photoperiodic responses were observed cleary in case of rush plants.