The auxin and phenolic contents, as well as phenylalanine ammonia-lyase (PAL)
activity, were determined in in vitro cultured shoots of
the recalcitrant-to-root rac mutant of tobacco, and
compared with wild-type shoots. The mutant and wild-type shoots showed similar
auxin changes during the culture cycle, but with higher contents for the
mutant. A transient peak of auxin (corresponding to the achievement of the
rooting inductive phase) occurred at day 14 in both types of shoots, but
earlier in the basal parts of the wild-type stems. The
rac shoots contained more phenolics, corresponding with
an increased PAL activity. The most abundant phenolic compound found in the
two types of tobacco was chlorogenic acid, which was more abundant in the
rac shoots. Rutin was also detected at a higher
concentration in the mutant shoots. Basal parts of wild-type shoots treated
with 10–3 M chlorogenic acid reacted by
accumulating auxins and, unlike untreated controls, did not form adventitious
roots. The relationships between these biochemical analyses in relation to the
growth limitation of the rac mutant, and the inhibition
of its root development, are discussed.
Mechanism for the hydrogen sulfide-induced growth limitation in wetland macrophytes