Studies in Short Day Vernalization of Barleys : 1. Differences in short day vernalization effects due to the degree of plant development

Abstract

Relations between short day vernalization effects and the degree of plant development due to ageing and differences of temperature and daylength, were studied, using the variety of naked barley, "Ichiwase" (winter barley type). The younger the plant was, the more pronounced was the vernalization effect. If plants had not received low temperature, plants of order than about 6 leaves of main stem had all the same effect, and even in plants of 12 leaves of main stem, heading was hastened by several days by the short day treatment. Heading was hastened by the short day treatment in plants which had received chilling for 0∼25 days at the stage of sprouted seeds, while heading was delayed in plants which had received chilling for 30 days or more. Chilling for 30 days was not enough to vernalize the plant completely in this experiment. The longer the plant had received chilling at the stage of sprouted seed, the shorter was the length of time from sowing to the beginning of short day treatment which could hasten the heading and at the same time the earlier was the nullifying of hastening of heading due to the increase of short days. When plants were sown on October 16, November 15, and December 15, 1959 and were grown outdoors under natural daylength, short day vernalization effects were decreased as the age of plants increased, and were nullified on the plants treated by short day on around December 10, December 30, and January 10, respectively. When plants had stet, treated by low temperature at the stage of sprouted seeds or during growth, short day vernalization effects were nullified at the early stage of growth. Short day vernalization effects were not nullified at the stage of double-ridge formation but at the stage when plants were vernalized to some degree. This degree of vernalization was lower than that by which the hastening of heading was maximum.