Studies on the Bulb Formation of Allium wakegi Araki

Abstract

Effects of daylength, temperature, and soil moisture on bulb formation in Allium wakegi Araki were investigated. Bulb formation in A. wakegi was induced by long daylength and high temperature conditions, as is also the case with onions. A low temperature period preceding the long daylength and high temperature phase served to fasten bulb formation. Low temperature requirements differed between two ecotypes, the “Japanese” and the “Southern” types, the former having a lower temperature requirement for such treatment.
Low soil moisture under long daylength conditions also enhanced bulb formation; under these conditions, endogenous abscisic acid in whole plants increased steadily, and auxin in the leaf blade increased at an early stage (only 5 days after water stress treatment). An increase in both abscisic acid (a growth inhibitor) and auxin (a growth promoter) seemed to be necessary for the induction of bulb formation. Further, the “Southern” type responded more quickly than the “Japanese” type to the low soil moisture conditions.