Liquid Culture Systems for in vitro Plant Propagation

502 Han Bouman & Annemiek Tiekstra
showed that these plantlets had a much lower Fe content (ca 40 %) than MS-
and Cu-plantlets. So maybe lowering of Mn-concentration on its own -
although growth is better- should be applied carefully. In contrast, plantlets
grown with increased Cu were much greener than MS-plantlets, but their Fecontent
was not increased.
4. General discussion
Mineral adaptations for tissue culture media consist usually of lowering
the concentration of the MS macroelements (e.g., half concentration of MS
or half concentration of nitrogen in rooting media), or screening a number of
ready-made media (MS, B5, DKW etc.). Suggestions to increase some
minerals, among others, Ca and Mg (Singha et al., 1987; George, 1993) were
made years ago, but have been generally ignored.
In our research, healthy young-adult leaf material was chosen for
elemental analysis (see above). Rugini’s medium (1984) was based on data
from young plant parts, i.e., shoots and embryos: in his medium, P was much
greater and Ca (much) less. Preliminary experiments with gerbera showed
that such composition was less beneficial for growth than the adapted
medium used here. Monteiro et al. (2000) used mineral analysis of adult
leaves of passion fruit for total mineral adaptation to define a specific
medium. Their successful medium had a greater concentration of Ca, P, Mg,
S, and especially Cu, than MS, confirming our findings. For Mn they used a
greater concentration than in MS, which contrasts our results where we had
an improvement of growth by reducing the Mn concentration, similar to
Kintzios (2001; see below). Cos Terrer and Frutos Tomas (2001) also used
adult leaf analyses for developing media for peach-almond hybrids. They
only adapted the macrominerals, but did make variations for each cultivar.
They compared growth on their media with growth on MS, but not DKW.
Higher mineral concentrations in the medium resulted in higher
concentrations in the plant for several elements, e.g., S and Ca (Singha et al.,
1990), but not for K. Gerbera plantlets from GAM had the same or even
greater K content as plantlets grown on MS or DKW in spite of the much
lower K concentration in GAM. On the other hand, plantlets from DKW had
a high S content. “Luxury consumption” can lead to depletion of the medium
of some elements, but because of redistribution within the plant, this does
not mean, necessarily, that at the same time there would be a deficiency in
the plant. With Cymbidium, P was almost exhausted in CAM (