Abstract
The experiments were carried out in greenhouse from November 1967 to May 1968 to investigate the environmental conditions affecting reproductive growth of red clover plants, using Kenland as early-flowering variety and Altaswede as late-flowering variety. The temperature in greenhouse was 25℃ in the daytime and 15℃ at night and fluorescent lamp (mean light intensity was 360 luxes) was used as supplementary light. The plants were grown under the conditions of short day (12 hrs.), long day (17 hrs.) and combinations of short day, long day and low temperature (2〜7℃). After the investigations in the greenhouse were over, Altaswede plants were sampled and weighed for top and root dry weight. The results are summarized as follows: 1. Growth and flowering of both early- and late-type were accelerated by long day. It was considered that long day was a basic condition for induction and acceleration of flowering. 2. Flowering of both early- and late-type was accelerated by low temperature treatment, when they were grown under their critical day-length. 3. The accumulation of accelerating effect of low temperature on flowering of early- and late-type was largest, when the plants were three months of age after germination. 4. The effect of day-length before and/or after low temperature treatment on flowering of Altaswede was greatest when plants were grown according to the following procedure ; Short day→Low temperature→Long day 5. The effect of day-length at low temperature on flowering was relatively small. 6. Altered day-length (short day→long day) delayed the growth of both types as compared with continous long day. However, in the case of Altaswede when the plants were three moths of age after germination, the ratio of plants with elongating-stems was increased more by this alteration of day-length than by continuous long day treatment.
