Liquid Culture Systems for in vitro Plant Propagation

Application of bioreactor systems 103
another strategy for producing progagules, which can be handled for direct
planting in the field. Micropropagation by axillary shoot proliferation is
typically a labour-intensive means of producing elite clones, but recently the
adaptation of air-lift, bubble column, BTBB, ebb and flood and temporary
immersion bioreactors for propagation of shoots and bud-clusters has
provided a workable means for scale up. Some of the most advanced plant
tissue culture work that has been progressed to research-scale bioreactors is
based on production of crop species such as Stevia rebaudiana, Begonia,
Chrysanthemum, apple, grape, pineapple, garlic and Phalaenopsis.
4.3 Somatic embryogenesis
Somatic embryogenesis also offers a potential system for large-scale
plant propagation in automated bioreactors. Conventional micropropagation
requires intensive labour which often limits its commercial viability and
application. Somatic embryos could be easier to handle since they are
relatively small and uniform in size, and they do not require cutting into
segments and individual implanting onto media during proliferation. In
addition, somatic embryos have the potential for long-term storage through
cryopreservation or desiccation, which facilitates flexibility in scheduling
production and transportation and therefore fits large-scale production. The
production of somatic embryos in bioreactors has been reported for a
number of species (for reviews see Denchev et al., 1992; Cervelli and
Senaratna, 1995; Moorhouse et al., 1996; Timmis, 1998; Ibaraki and Kurate,
2001; Paek and Chakrabarty, 2003), but many improvements are needed for
the practical automatic somatic embryo production systems that can cope
with synchronization of the somatic embryo development, identifying the
occasional embryo abnormality during culture, and overcoming the
difficulties in embling acclimatization.
5. System examples
5.1 Ginseng
Ginseng, Panax ginseng of the Araliaceae family, is one of the most
valuable oriental herbs. It (usually, the dried root) has been used as a healing
drug and health tonic in countries such as China, Japan and Korea since
ancient times (Tang and Eisenbrand, 1992). In recent years, ginseng has
been used increasingly as a health tonic, in the form of a variety of
commercial health products including ginseng capsules, soups, drinks and