Short-period test of growth, bulbing, leaf-fall down and regrowth of onion (Allium cepa L.) under different daylength controlled by supplemental lighting

摘要

The possibility of generation shortening by controlled daylength in onion (Allium cepa) was studied. Two cultivars 'Paechongjosaeng' and 'Chenjudaego' were grown under 12.5, 13.5, and 14.5 h, and natural daylength. The period of reaching maximum number of leaves and plant height was shortened under longer daylength in early cultivar 'Paechongjosaeng'. Bulb diameter increased rapidly after reaching maximum number of leaves which was a good indication of the development of bulb. Bulbing (over 2.0 ofbulbeck diameter ratio) was shown after 60, 49, and 35 days from supplemental lighting on the 12.5, 13.5 and 14.5 hour in 'Paechongjosaeng' and 54 days on the 14.5 hour in 'Chenjudaego', respectively. The rate of bulb over 2.0 of bulbing ratio increased under longer daylength and each individual showed much the same in bulbing under longer daylength. In the longer daylength, leaf fall-down was advanced and occurred in a short period. The rate of leaf fall-down was higher in 'Paechongjosaeng' under longer daylength than 'Chenjudaego'. The effect of days from supplemental lighting on regrowth was shortened in the case of longer daylength in 'Paechongjosaeng'. However, the difference of days from leaf fall-down to regrowth was less than that of days from supplemental lighting within daylengths or cultivars. The above results indicate that the period of the characteristics test were shortened to 180 days under a 14.5-h daylength by supplemental lighting in 'Paechongjosaeng', but required longer daylength than 14.5 h in 'Chenjudaego'. Screening in the early generation on the long day over critical daylength was unfavourable as individual variations were not clearly distinguishable.