The effect of light and of explant orientation on the regeneration and subsequent growth of bulblets on Lilium longiflorum Thunb,bulb-scale sections cultured in vitro

Lilium longiflorum, cultivar ‘Osnat’, bulb-scale sections were cultured in the light and in the dark with explants placed with their dorsal (abaxial) side on the medium, and in the dark with their ventral (adaxial) side up or down, or in the upright or inverted position. Scale sections regenerated bulblets, roots and callus. In all cases, bulblets developed only on the ventral side of the scale. Light did not affect the regeneration capacity of the scale piece but did significantly affect bulblet growth. Bulblets developing in the light were small and bore many leaves. In the dark, a smaller number of bulblets, which were much larger but bore fewer leaves, developed. In the light, leaf dry weight was double that of bulb dry weight, whereas in the dark this proportion was reversed. In contrast to light, explant orientation greatly affected regeneration percentage. Scale sections planted with their ventral side down regenerated fewer and smaller bulbs, less root, but much more callus than those with their dorsal side down. The upright and inverted positions also reduced the number of bulblets regenerated and increased callus formation.