Abstract
1. Vernalized seeds of two winter barley varieties, HASHIRIHADAKA and H. spontaneum leigrum, were grown under short day (8 hr.) or long day (24 hr.) for definite number of days, then transfe-rred to reverse day length condition and the effect of conversion of day length to the heading was investigated. 2. When the plant was transferred to long day (LD) after short day (SD) treatment, the number of days from sowing to flag leaf emergence increased with the increasing pre-treatment of short day. But the number of days from transfer to flag leaf emergence decreased in HASHIRIHADKA and not changed in H. spoletaleeulee leigrum. The former is an early variety and the latter is a late one. 3. When the plant was transferred to SD after LD treatment, the number of days from sowing to flag leaf emergence decreased with the increasing pretreatment of LD and the number of days from transfer to flag leaf emergence also decreased. But the amount of decreasing was different between varieties. When plants were transferred to SD after 20 days treatment of LD, they headed as well as under continuous illumination. But if we look at the leaf numbers, the plant treansferred to SD after 8 (HASHIRIHADAKA) or 6 (H. spolctaneueec Ieigrulec) days treatment of LD, headed on same leaf. numbers to the plants grown under continuous illumination. These differences will be explained by increasing length of flag leaf and comparatively long durations for expansion of leaves with decreasing long day pre-treatment.
