|dc.description.abstract||A modified Berthelot (1934)-Knop (1865) solution was
found to support the growth of rose pith segments while
Murashige and Skoog's (1962) medium did not. Possibly the
NH(4)+ content of the latter medium is toxic to rose tissue.
The best callus growth was obtained with indolebutyric acid
(IBA), which was superior to naphthaleneacetic acid (NAA),
indoleacetic acid (IAA) and 2,4 dichlorophenoxybutyric acid
(2,4-DB) at the concentrations tested, while gibberellic
acid (GA) greatly enhanced callus formation in the presence
of both IBA and kinetin. Occasional differentiation of
shoots was observed both in cultured pith segments and in
callus formed at the basal cut surface of the shoot tips.
However, the precise culture conditions required for differentiating
rose pith and callus tissue remain unknown.
An interaction was found between NAA and kinetin
with regard to root and leaf development in shoot tips.
Root formation took place only in the absence of kinetin
and in the NAA range of 0.5 to 2.0 mg/l, while normal leaf
development occurred only in the absence of NAA and in the
presence of 4.0 to 18.0 mg/l kinetin. Neither any combination
of NAA and kinetin nor the sequential application of
growth substances induced both root and shoot growth. Furthermore,
shoot tips sampled in late summer formed roots
much more readily than tips sampled in late winter.
GA reduced the favourable effect of high kinetin treatments
on leaf development. Different species of auxin affected
growth of the shoot tip in different ways. IAA did not
inhibit growth of the shoot tip in the same manner as was
observed for NAA, IBA and 2,4 dichlorophenoxybutyric acid
It is concluded that further experimentation with
different ratios of various species of auxin and cytokinin,
as well as the sequential administration of growth substances,
may lead to the successful culture of intact
plantlets from rose shoot tips and shoot apical meristems,
and ultimately to possibly virus-free rose plants.||en