抄録
The reversal of the short day vernalization effect by high temperature and by long days were studied to make clear the role played by short day vernalization in the heading of barley. Low temperature vernalization was reversed at 18°C or more high temperature and this effect was more pronounced as the temperature was high. When the different degrees of temperature were given during the short day treatment, the short day vernalization effect was most pronounced at 18°C and was less pronounced as the temperature was higher than 22°C, though the heading was hastened more or less by the short day treatment even at 30°C. After the short day treatment the retardation of the heading by the high temperature treatment was less pronounced than the above case. The short day vernalization effect indicated early to be stable to the high temperature treatment as compared with the low temperature vernalization effect. In plants which had received no chilling at the stage of sprouted seeds, the hastening of the heading by the short day treatment at 26°C or 30°C was not so large as that at the open air, but in plants which had received chilling, the hastening of the heading by the short day treatment under both temperature conditions were same. There was no relation between the decrease of the short day vernalization effect by high temperature and the winter habit of varieties. In the variety "Kobinkatagi No. 36", such a decrease was something different from those in other four varieties. The hastening of the heading by the short day treatment which was proceeded under different conditions of temperature was more largely affected by the high night temperature than by the high daytime temperature. This reduction of the hastening was closely related to the length of time of the high temperature treatment during 24 hours. This fact suggests that the decline of the short day vernalization effect by high temperature depends more on the partial destruction of the effect of short day treatment by high temperature than on the retardation of the short day reaction by high temperature. This devernalization of the short day effect is pronounced at about 26°C or more high temperature. The short day vernalization effect was reduced when long days were intercalated among short days. This devernalization effect was more pronounced when long days were intercalated separately than when intercalated in a series. The short day vernalization effect was completely reversed when one short day and one long day were given alternately. This devernalization effect was more pronounced when long days were intercalated among the former half of short days or when the temperature during intercalated long days was high. The short day vernalization effect was pronounced even at high temperature such as sprouted seeds could not be chilled. This fact suggests that the short day vernalization effect may play an important part in the heading of barley sown in autumn.
