Relationship between bulb growth of Lilium japonicum Thunb. in the field and bulblet formation on in vitro cultured scales

Experiments were conducted to clarify the relationship between seasonal changes in bulb growth of Lilium japonicum thunb. in the field under natural conditions and bulblet formation on in-vitro cultured scales. When scales are detached from a bulb, vestiges of stems from past years are detectable on the basal plate. The year, the scales were formed, was identified by the positions of the residual stems on the basal plate. Each year, a new daughter bulb, consisting of about 7 scales, which develops within the mother bulb and the growth of the new shoot, which occurs between April and July, consume 3 to 4 outer-scales of the mother bulb. The bulbs were collected on 10 March, 1 July and 14 October, and their scales cultured for 13 weeks. The rate of bulblet formation on the scales collected on 10 March was fastest. The formation rate and fresh weight gain of the regenerated bulblets, which formed on the outer sales, were faster than those on the inner scales. We conclude that to regenerate bulblets by in-vitro scale culture,early spring is the optimum time to collect the bulbs