Liquid Culture Systems for in vitro Plant Propagation

236 Tino Hempfling & Walter Preil
Figure 4: (A) Effect of TDZ (0.1 and 0.5 mg l -1 ) on adventitious shoot proliferation of
Phalaenopsis cv. Jaunina after 7-week culture. (B) Shoot cluster after 12-week culture on 0.5
mg l -1 TDZ-containing medium.
3.3 Effect of TDZ-containing medium on shoot size
Varying periods of TDZ exposure affects not only the multiplication and
fresh weight rate but also the shoot size. Figure 5 shows the shoot size
categories obtained from a twelve-week culture and a seven-week culture on
TDZ-containing medium.
Separating the clusters of adventitious shoots into single propagules,
three categories were obtained from the twelve-week culture on TDZmedium:
50 % of the shoots fell short of 1 cm, 41 % were of 1-3 cm and 9 %
exceeded 3 cm in length, respectively. For practical purposes, 50 % of the
shoots smaller than 1 cm are suitable for use as inoculum for the next
propagation cycle, whereas 50 % of shoots larger than 1 cm can be rooted
either in TIS or on solid medium following the standard procedure.
The seven-week culture on TDZ-containing medium followed by five
weeks on TDZ-free medium gave rise to 18 % of shoots smaller than 1 cm,
56 % were of 1-3 cm and 26 % exceeded 3 cm in length, respectively
(Figure 5). This demonstrates that the categories of shoot size can be
manipulated by the duration of TDZ- exposure depending on the
requirements of the propagation process.