The role of night temperature in the bulbing of onion (Allium cepa L.)

Abstract

Onion (Allium cepa L.) cultivars Creamgold and Gladalan Brown were grown at three day lengths (13, 14 and 15 h) and three day temperatures (22, 26 and 30¦C) in the Canberra phytotron. In each case bulbing was slower whcn the night temperature was 15' below day temperature than at 5¦ below day temperature. The cultivar Gladalan Brown, growing at 13 h day length and 26¦C day temperature, bulbed faster when the first half of the 11 h night was at 21¦ and the second half at 11¦ than in a 11¦ then 21¦ night. The number of days from sowing to the start of bulbing decreased with increasing night temperature. The rate of bulbing after initiation increased with increasing night temperature.