Abstract
Some informations on expression of growth type and flowering of some red clover varieties, investigated in Sapporo, Hokkaido (43°00' N. Lat.), and in Tomobe, Ibaragi Prefecture (36°22' N. Lat.), were summarized as follows : 1. Expression of growth type of red clover varieties was almost similar in cases of March 15-May 15 seeding in Sapporo. This showed that induction of florigenic stimulus was affected by critical day-length, not by accumulated one. 2. Medium type of red clover varieties in June 1-15 seeding in Sapporo was intermediate in their stem elongation, showing wide distribution as 0-IV Types in their growth type expression; while, in July 15 seeding, stem elongation was hardly observed. This suggested that there must have been an essential and effective stand age of red clover plant for induction of florigenic stimulus, responding to daylength. 3. Mean flowering date of red clover varieties tested in Tomobe was 15-20 days earlier in April 15 seeding; while, 30-40 days earlier in June 1 seeding, in which the expression of their growth type was almost similar in both Tomobe and Sapporo, than that in Sapporo. From the mean flowering date and the daylength in both places, the stand age of red clover plant above mentioned was supposed to be about 60 days after seeding in Sapporo; while, about 45 day after seeding in Tomobe. 4. For seed increase of red clover varieties, it is desirable to consider the daylength and the stand age of red clover plant for induction of the florigenic stimulus in corresponding places, in order to avoid a shift of characteristics in red clover varieties. For example, in case of varieties tested, which are adaptable in northern areas, seed increasing place should be chosen in a more northern area from the location of fifteen hours in the longest possible duration of sunshine (about 40°00' N. Lat.), and also, seeding should be done at date of 60 days or more before the latest date of fifteen hours in the possible duration of sunshine. This should be also considered in identification on characteristics of red clover varieties. 5. Growth type seems to be more reasonable as a marker character than flowering, for the identification on characteristics of red clover plant population, especially for that in diverse latitudes.
