Production of commercial bulbs of Lilium rubellum baker: Changes in carbohydrates in bulblets and sugars of liquid medium during their culture

Abstract

1. Bulblets of Lilium rubellum were cultured for 16 weeks in liquid MS medium containing 100, 150 and 250 mmol · liter-1 (mM) sucrose (referred to as 100, 150 and 250 mM sucrose medium, respectively). The 250 mM sucrose medium enhanced bulblet growth the most. The greatest gain in fresh weight occurred between 4 and 8 weeks after culture. The ratio of dry to fresh weights (DW/FW) of bulblets cultured in the 250 mM sucrose medium was always highest. 2. Three sugars (sucrose, glucose, and fructose) were detected in the autoclaved MS medium. When bulblets were cultured in the liquid sucrose medium, the concentration of glucose and fructose in the medium increased until week 4 as the sucrose concentration decreased. Sugars in the 150 mM sucrose medium were nearly depleted by week 8, whereas those in the 250 mM sucrose medium persisted for 12 weeks. The growth rate of the bulblets declined as sugar concentration in the medium decreased. 3. The sucrose content in bulblets, cultured in each medium, increased until week 4, then decreased. However, in bulblets, cultured in the 250 mM sucrose medium, the sugar content increased again after 12 weeks of culture, while starch content decreased. Hence, it appears that the starch accumulated in the bulblets was hydrolyzed to glucose. These results indicate that the growth of bulblets of L. rubellum cultured in liquid medium can be promoted by subculturing the bulblets after 8 to 12 weeks of culture.