Liquid Culture Systems for in vitro Plant Propagation

170 M. Berthouly & H. Etienne
2.3 Systems with partial immersion and a liquid medium
renewal mechanism
The plant explant is always positioned on a culture support (agar
medium, propylene screen, cellulose plugs). Liquid culture medium is
frequently supplied, then withdrawn into a drain-off recipient vessel, so as to
imbibe the support, stabilize the composition of the culture medium and
extend the duration of subcultures, whilst avoiding or postponing the need to
change the medium. Only the base of the plant material is partially
immersed. Two models have been published:
– Aitken-Christie and Jones (1987) and Aitken-Christie and Davies (1988)
proposed a semi�automatic process in large polycarbonate containers
measuring 250 x 390 x 120mm (Figure 1B). In their system, Pinus shoots
were grown on an agar medium, with automatic addition and withdrawal
of liquid medium by peristaltic pumps on a periodic basis. The liquid
from the fresh medium recipient vessel came into contact with the
explants for 4 to 6 hours, using a vacuum suction system, then went to
the drain-off recipient vessel. This system follows on from the work by
Maene and Debergh (1987), who had shown the positive effects of a
adding liquid nutrient medium or auxins in the final in vitro stages.
– Simonton et al. (1991): their system featured a computer-controlled
pumping apparatus that intermittently supplied liquid medium to plants
cultured in 7-litre vessels (Figure 1C). Plant material rested on a
perforated polypropylene screen that was attached to the inside of the
vessel. Control capabilities included medium introduction and depth
regulation within four individual culture vessels, medium cycling on an
assigned schedule, schedule adjustment during a culture period, and
medium replacement.
2.4 Systems with complete immersion by pneumatic driven
transfer of liquid medium and without medium replenishment
Different systems were described after the first publication by Alvard
et al. (1993). These include the most recent temporary immersion systems.
They are simple and easy to use. They enable contact between all parts of the
explant and the liquid medium, along with complete renewal of the culture
atmosphere by forced ventilation, which drives the liquid towards the plant
material. The plant material can be placed in the container in bulk, removing
the need to position the plant material on a support. Such systems include
pneumatic transfer of the medium from a reservoir tank to the container
holding the plants. To avoid excess tubing, these two compartments are