Effects of Low Temperature at Night during Nursery Period on the Early-Maturing Varieties of Rice.

In order to investigate the physiology of rice varieties for the purpose of establishing the early-or late-sowing system in the warmer region of Japan,the effects of low temperature at every night during nursery period were examined. This experiment was carried out with 4 early-maturing varieties.The night temperature and day length during the nursery period (34 days)were as follows : (1)Low-temperature(average 8.1℃.)and short-day treatment at every night(16 hours). (2)High-temperature(average 20.3℃.)and short-day treatment at every night(16 hours). (3) Natural temperature and day length. 2.The premature heading of the varieties which were sensible to hightemperature or short-day treatment was hindered by the low temperature inspite of the short-day condition. 3.When the well nourished condition was given after the low-temperaturetreatment,it was generally observed that the heading time retarded and the total weight of ears on each plant increased,accompanied by the increase innumber of leaves in the main stem. 4. The nutrient supply to respective plant body after the low-temperature treatment seemed to increase comparatively,because each plant had become dwarfed during the treatment. It is therefore presumed that the transition from vegetative growth to reproductive growth in this experiment was checked not only by the low temperature itself but also by the nutritive condition after the treatment.

水稲早生品種

夜間低温処理