Liquid Culture Systems for in vitro Plant Propagation

Application of bioreactor systems 107
air supply. Regenerated shoots with well-developed roots were acclimatized
and then grown in a greenhouse (Ket et al., 2003).
5.5 Apple
Many woody plant species are sensitive to the liquid medium
environment in a detrimental way. Hyperhydricity frequently occurs with
tissues grown in or on liquid media as a result of contact with the liquid and
other micro environmental parameters present at that time (Christie et al.
1995). Recently we developed a novel type ebb and flood bioreactor system
for the mass propagation of apple rootstock M9 EMLA. Although the
multiplication rate was highest in immersion culture (5-litre BTBB), a large
number of hyperhydric plantlets was produced. With the ebb and flood
system, hyperhydricity was reduced as compared to the immersion system.
In an attempt to completely eliminate the hyperhydricity, we supplied
compressed air inside the bioreactor chamber to reduce the humidity. This
approach significantly reduced the hyperhydricity during the bioreactor
culture of apple plantlets (Chakrabarty et al., 2003) (Figure 5a). Plantlets
regenerated during bioreactor culture were transferred to hydroponic culture
for ex vitro rooting and acclimatization (Figure 5b).
5.6 Chrysanthemum
We investigated the effects of environmental factors (PPF, air
temperature, air volume, medium composition, inoculation density and types
of medium supply) on the growth and quality of Chrysanthemum plants in
bioreactors (Kim, 2001). Optimum culture environments for bioreactor
culture (10-litre air-lift column type with raft) were: a NH4 + :NO3 - ratio of
20:40, 25 o C air temperature, 100 mmol m -2 s -1 PPF, 0.1 vvm air volume and
an inoculation density of 40 to 60 nodal cuttings per bioreactor culture
(Figure 5c). Supplementation of the culture with sugar-free medium after 8
weeks of culture resulted in higher growth rates as compared to
supplementation with sugar-containing medium.
5.7 Garlic
Garlic is vegetatively propagated, but its low propagation rate as well as
long time to produce a sufficient number of seed bulbs for practical
cultivation led to the development of an in vitro protocol for
micropropagation. However, the rate of multiplication and growth of
microbulbs during in vitro culture are not sufficiently high to be of practical