Inhibition of bulb development of Allium wakegi Araki by covering with far-red-intercepting film in summer

Effects of covering with film which has a low transmittance in the far- red (FR) region on bulb development of Alliurn wakegi Araki during summer were investigated. After planting the bulbs on July 6 and 28, the plants were grown under tunnels covered with FR-intercepting film, clear film combined with a layer of white cheesecloth, or without film. Fresh weight of basal leaf sheath and the bulbing ratio (maximum diameter of the basal leaf sheath/minimum neck diameter) under the clear film and without film increased with time after planting, but these increases were suppressed under the FR-intercepting film. Formation of bulb scales, swollen bladeless leaves, was also suppressed under the FR- intercepting film. When bulbs were planted on July 28, all plants grown under the clear film and without film formed bulb scales, whereas no plants grown under the FR-intercepting film formed them. Plants grown under the FR-intercepting film had the highest leaf chlorophyll content of those under the three treatments. The interception of FR light did not reduce leaf length or shoot fresh weight. These results indicate that the covering with the FR- intercepting film is useful for summer cultivation of A. wakegi because it inhibits bulb development without impairing other characteristics, such as leaf color, leaf length, and shoot fresh weight.