Narcissus and Daffodil

220 C. Codina
they might be more suitable for investigating the mechanisms triggering alkaloid
accumulation than shoots or plantlets. Furthermore, somatic embryos are easier
to handle biotechnologically than more complex structures. Embryogenic strains
may, therefore, be of special value in further investigations of alkaloid formation
in N. confusus in vitro.
Plantlets regenerated from either shoot-clumps or somatic embryos were found
to produce alkaloids. Table 7.1 shows that only the content of galanthamine
increased with tissue differentiation. A possible explanation is that the differentiation
stage could influence the biosynthetic pathway of these alkaloids in a different
manner. Galanthamine and N-formylnorgalanthamine derive from a para-ortho
oxidative phenolic coupling, whereas haemanthamine and tazettine result from
para-para coupling. In general, the more tissue organisation there is, the higher
the alkaloid content. Plantlets regenerated after 6 months were characterised by a
well formed bulb and emerging leaves, and seemed to be the best material for
experiments on galanthamine production.
Bulb-derived plant material
Shoots were obtained directly from the bulbs by using the ‘twin-scaling’ technique
(Hanks and Jones, 1986), and they were classified according to the position of the
scales in the bulb: internal, central or external. The alkaloid content was analysed
in the scales initially and in shoots obtained from each kind of scale (Sellés, 1996).
The different kinds of explants were maintained in the same culture conditions
for 5 months as previously described (Bergoñón et al., 1996), and then the alkaloids
were analysed in samples from the regenerated shoots and their respective scales
(Figure 7.4). In all cases, the major alkaloids were haemanthamine and galanthamine,
in that order, and the alkaloid profile of the regenerated shoots was
found to coincide with that of the bulb scales, both qualitatively and quantitatively.
It is important that all the shoots induced after 5 months are small shoots with
the capacity to accumulate galanthamine. Therefore, these explants, after being
mg/g DW
1.0
0.8
0.6
0.4
0.2
0.0
Outer Middle Inner Average
Shoots
NFNGAL GAL HAEM TAZ
A
1.0
0.8
0.6
0.4
0.2
0.0
Outer Middle Inner Average
Scales
NFNGAL GAL HAEM TAZ
Figure 7.4 Alkaloid content in shoots (A) and their respective twin-scales (B) according to
their position in the bulb (values represent means of three replicates). For
abbreviations, see Figure 7.1.
mg/g DW
B