STIMULATION OF IN VITRO BULBLET GROWTH IN GALANTHUS SPECIES WITH SUCROSE AND ACTIVATED CHARCOAL

Abstract

We report here a reliable method to stimulate growth of in vitro-produced bulblets of Galanthus species to a size suitable for acclimatization. Proliferating bulblet cultures, from bulb chip explants, were induced and maintained on MS medium supplemented with 30 g/L sucrose, 1 mg/L BA and 0.1 mg/L NAA. The six treatments, prepared in plant growth regulator-free MS medium, were 30 or 60 g/L sucrose in all combinations with 0, 1 or 5 g/L activated charcoal. Fifteen replicates per treatment per plant type (G nivalis, G nivalis 'Flore Pleno' and G. elwesii) were inoculated with bulblet clumps containing 2-4 bulblets. Assessments were made after incubation for 16 weeks at 18°C with 16h photoperiods. Even in the absence of plant growth regulators the cultures continued to form new bulblets in all treatments. Bulblet growth was greatly stimulated by the addition of activated charcoal. In contrast, doubling the amount of sucrose in the medium to 60g/L had only a marginal effect on bulblet growth in the absence of charcoal. Addition of charcoal and sucrose together was found to have a synergistic effect on bulblet growth, in that the benefit of adding the higher rate of charcoal could be seen at only the higher sucrose concentration. Charcoal also induced the formation of large numbers of roots and stimulated root elongation. Bulblets had a normal anatomy in longitudinal section, and, although many of the bulbs sprouted in vitro and lateral bulb units developed in larger bulbs, none formed flowers. Thus it is expected that in vitro-produced bulbs will require either flower initiation treatment(s) or a minimum of one season in field conditions to achieve flowering size.