Effects of Day Length on Flowering and Rhizome Swelling in Ginger (Zingiber officinale Roscoe)

Abstract

Photoperiodic treatments were carried out with three Japanese cultivars (`Kintoki', `Sanshu' and `Oshoga') of ginger (Zingiber officinale Roscoe). As day length was increased from 10 h to 16 h, the vegetative growth of the plants was enhanced, whereas it was inhibited and rhizome swelling was promoted as the day length was decreased from 16 h to 10 h. Further increase in day length from 16 h to 19 h did not give any rhizome swelling, and resulted in the lowering of the growth increment. The cultivar `Sanshu' was most sensitive to photoperiod for rhizome swelling, but `Oshoga' was relatively insensitive. In `Sanshu' and `Oshoga', many flower stalks bolted under the day length of 13 h and 16 h, but they emerged slightly or not at all under the day length of 10 h, ND (decreasing natural daylength) and 19 h. The photoperiodic response to flowering of `Kintoki' was not very clear.