Bulblet Initiation Research Articles

Stimulation by auxin and sucrose of bulbil formation in vitro by single leaf cultures of Narcissus.

Bulbil formation in vitro by single leaf explains from shoot clump cultures was investigated for Narcissus cultivars St Keverne and Havera. Single leaf explants (30-50 mm leaf with attached basal plate tissue) formed bulbils very infrequently unless cultured on media containing both auxin and a high concentration of sucrose whereas auxin was not necessary for bulbil formation by shoot dump cultures. As well as showing much stronger stimulation by auxin, bulbil initiation and development were more strongly inhibited In BA in single leaf cultures than in shoot dump cultures. Partitioning of dry matter into bulbils was generally lower in single lent cultures than in shoot clump cultures but was more sensitive to growth regulators. Optimal sucrose and auxin concentrations for bulbil development by single leaf cultures were investigated. Bulbil formation in the presence of NAA was strongly stimulated by 176 mM sucrose for both cultivars but there were genotypie differences in auxin responses, St Keverne showing good bulbil development with 0.54 μM NAA, 5.4 μ 1AA and 5.4 μM 1BA und Hawera responding only to 27 μM LAA. It is concluded that single leaf cultures could provide a simple system for investigation of the regulation of the regulation of Narcissus bulb initiation and development.

Effects of bulb desiccation and storage on the in vitro propagation of hyacinth

The effect of long-storage and silica gel desiccation of hyacinth bulbs ( Hyacinthus orientalis L.) on in vitro bulblet formation was investigated. Bulbs of 3 cultivars were stored at 25°C and 50–60% relative humidity for 17 months. This long-term storage of bulbs markedly enhanced bulblet initiation from scales and growth of regenerated bulblets. Bulbs of 5 cultivars were desiccated with silica gel for 5 and 20 h before in vitro propagation. The total number of bulblets increased as a result of 5 h desiccation with silica gel. Bulb desiccation for 20 h caused a large increase in the growth rate of bulblets. This desiccation treatment with silica gel is a practical method to obtain many and more regenerative explants in the in vitro propagation of hyacinth.

Factors affecting twin-scale propagation of narcissus

The effects of several factors on bulbil yields obtained by twin-scaling were examined in 4 narcissus cultivars (representing poeticus, trumpet and large-cup types). Bulbils were initiated on twin-scales prepared at any time of year, but grew satisfactorily only if twin-scaling was carried out between June and September. Large twin-scales initiated more bulbils, but smaller twin-scales were also effective propagules and gave high rates of multiplication and bulbils with high relative growth rates. Twin-scales cut from the outer-most scales initiated most bulbils, but more of those bulbils produced from the more central scales were recovered after 1 year; those from intermediate scales produced most and heaviest bulbils after 1 year. Partial loss of the basal plate had no effect on bulbil initiation. Optimum bulbil initiation, emergence and first-year recovery rates occurred following incubation at 15 or 20°C; at 25°C these responses were cultivar-dependent. Bulbil yield after 1 year was greater following incubation for 16 weeks compared with 12 weeks. There was little effect on bulbil yield of cold (9°C) or warm (35°C) treatments of the parent bulbs prior to twin-scaling, except for a marked reduction in the numbers of bulbils initiated when the warm treatment immediately preceded twin-scaling. When the propagules were grown on in a frost-free greenhouse (minimum, 5°C) bulbil yields were higher than from those grown either in a warm glasshouse (minimum, 18°C) or in the open; an initial cold period (5°C) given before the propagules were placed in the frost-free house also reduced yield.

Studies on the physiology of hyacinth bulbs ( Hyacithus orientalis L.) IV. Hormonal regulation of induction on roots and bulblets in Hyacinthus orientalis L. grown in culture

The purpose of this work was to study the hormonal regulation of root and bublet formation in Hyacinthus orientalis L. grown in culture. Hyacinth bulbs, cv. Lady Derby, a few months old, were cultured on Murashige and Skoog's (MS) medium in 0.6% agar in the presence of different concentrations of auxin (α-naphthaleneacetic acid, NAA) or cytokinin (benzyladenine, BA). The regeneration of roots and bulblets was found to be dependent on the levels of growth substances added to the basic medium (MS). The best combination for bulblet initiation was 1 ppm of NAA and 10 ppm of BA. NAA was the only necessary hormone for callus formation and root differentiation.