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ŠUMARSKI LIST 7-8/2008 str. 36     <-- 36 -->        PDF

B. Pintarić: MIKROPROPAGACIJA BIJELE TOPOLE (Populus alba L.) Šumarski list br. 7–8, CXXXII (2008), 343-354
tion mediums. However, plant growth rate in M1 medium was more distinct
compared to M2 medium, where this relationship changed very quickly and
clearly in the three following passages. Thus, the M2 medium proved superior
for long-lasting use of these explants under in vitro cultures.

A part of the explants was “sacrificed” at different time intervals in order
to obtain and measure mean fresh and dry mass values. After “sacrificing”
the explants and collecting fresh and dry mass data, some basic statistical
data were calculated (Table 4) for the growth rate of the plant material under
in vitro conditions. According to the data, the shoots cultivated in the M1
medium had mean fresh mass values of 0.04022 g and dry mass of 0.00888 g.
The subsequent control measurements showed the mean fresh mass value of
0.03588 g and dry mass value of 0.00630 g. On the other hand, the explants
cultivated in the M2 medium showed fresh mass values of 0.03851 g and
0.00743 g and dry mass values of 0.02988 g and 0.01397 g.

Isolated shoots sized about 3-4 cm showed 100 % rooting under in vitro
conditions after being planted into the rooting medium (Z) with the addition
of 0.1 mg/l IBA (Indol Butric Acid) for seven days and their transplanting into
the basic hormone-free medium (BH) in the following tree weeks. In the
acclimatization stage, the rooted plants were transferred from the sterile containers
in which they were cultivated into the soil substrate (soil and sand at

3:1 ratio) outside the chamber climate.
The root system was cleaned from the medium particles with agar using a
spray of sterile distilled water. The plants were transplanted into the soil substrate
previously sterilized with fungicide. These young plants did not have a
sufficiently developed cuticula, a functional stomatal apparatus, a good vascular
connection between the root and the shoot, well developed root hairs,
etc., so it was necessary to acclimatize them gradually to the ex vivo conditions.
This was achieved with temporary protection of the young plants with
sterile glass containers. The removal of the containers was strictly controlled
and the period of removal was lengthened every day in order to enable gas
exchange. On the other hand, for the first seven days the plants were watered
with sterile distilled water and after that with tap water.
Although this is usually a critical stage, all the transplanted individuals
managed to acclimatize to relatively low air humidity prevailing in external
conditions (ex vitro conditions). No phenotypal changes were observed on the

o pplant material either in in vitro or i
nn vivo conditions during the experiment.