Liquid Culture Systems for in vitro Plant Propagation

Application of temporary immersion in Phalaenopsis 241
The fresh weight increase was 20.5-fold after twelve weeks on TDZmedium
compared to a 17.4-fold increase after seven weeks TDZ-exposure
(Figure 3). This difference was statistically not significant indicating that
TDZ plays a minor role in total biomass production. In contrast, shoot size
categories obtained after separating the clusters into single propagules were
strongly affected by the different periods of TDZ-exposure (Figure 5). As
expected more small shoots (50 % < 1 cm) developed after twelve weeks on
TDZ-medium, whereas after seven-week culture on TDZ-medium in total 82
% of shoots were larger than 1 cm. This result is of practical importance for
commercial propagation since the output of the required shoot size can be
adjusted by the culture time on TDZ-medium.
4.3 Rooting
When two immersions per day of ten minutes each were used only 63.5
% of the shoots developed roots. An increase was achieved after four or six
immersions resulting in 88.7 % and 87.4 % rooting. These frequencies are
obviously optimal for root development in Phalaenopsis cv. Jaunina. There
are no data from other cultivars. As known from TIS cultures of other plant
species the recommended immersion frequencies can vary widely from
seconds to hours (for references see Etienne and Berthouly, 2002). This
holds true for development of shoots, somatic embryos or tubers.
5. Conclusion
TIS has proved to be an efficient tool for propagation of Phalaenopsis.
The reason for the high multiplication rates and fresh weight increases may
be not only the uptake of nutrients and hormones over the whole plant
surface but also the daily multiple air exchange ventilating gaseous
compounds like ethylene and CO2. Optimum immersion frequency supports
this beneficial gas exchange.
No economic data for the application of TIS versa conventional in vitro
culture on solid media is yet available in Phalaenopsis. For sugarcane
propagation, a cost reduction of 46 % was calculated for TIS compared to
cultures on agar medium (Lorenzo et al., 1998). Pineapple multiplication in
TIS saved 20 % of production costs per plant in comparison with
conventional liquid cultures (Escalona et al., 1999). Since various kinds of
automation steps are applicable to TIS, a considerable reduction of costs,
especially in those for manual labour, can also be expected for Phalaenopsis
in future.