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ŠUMARSKI LIST 5-6/2016 str. 71     <-- 71 -->        PDF

manifested different behaviour patterns in dependence of certain geographic/regional clone origin. After 27 days of subcultivation on a shoot multiplication medium, there were differences in height, size of internodes and leaf blades, as well as in multiplication rates, as shown in Figure 1.
No correlation was established between the heights of formed clone microplants during multiplication with the heights of the same clones preserved in situ.
Shoot clusters obtained from wild cherry multiplication, especially clones which did not reach 1.5 cm in height, were subcultivated on the elongation medium, where an increase of shoots in the shoot clusters was observed. After 20 days, microcutings were excised and transferred to the rooting medium. The elongation phase is exceptionally important because tiny rooted plantlets cannot acclimatise successfully, thus incurring severe losses.
In this research, subjecting the shoot clusters to dark periods proved less efficient because a very low percent of microplantlets started growing. At the same time, shoot quality decreased as the shoot lost a healthy green colour. Shoots that were elongated in the dark abruptly increased their internodes and became thinner, while the leaf blades remained small and pale. It is very likely that dark periods in the elongation stage could result in the deterioration of shoot tips. This method of plant elongation yields potted microplants of exceptionally uneven appearance.
In order to overcome these problems, the shoot clusters were transferred to a culture medium supplemented with Kinetin 0.5 mg/L and GA3 0.2 mg/L for 20 days, despite the fact that one more elongation subcultivation raised the cost of the process. This resulted in uniformly elongated shoots with elongated internodes. The leaves retained their green colour, the shoots did not thin out and no tips were degenerated. These microcuttings rooted more rapidly and achieved a very high survival percentage in the acclimatization stage.
It is important to obtain good quality plantlets with sturdy leaves and with root systems capable of performing their role in the acclimatisation stage. In this research, the selected medium for in vitro rooting of wild cherry and a combination of growth regulators IAA and IBA in the in vitro condition proved successful.
The plantlets obtained by micropropagation were rooted during April and May 2008. The quantities ranged from 50 to 150 plants, depending on the clone and the time of introduction into the initial culture. Owing to the fact that only well formed plants of good quality were used for rooting, the rooting success was above 90%.
After 14 days, wild cherry plantlets derived from the 23 studied clones were successfully rooted and continued growing and developing their roots. In the in vitro rooting stage they grew up to 5 cm in height. The rooted plantlets of wild cherry developed normal internodes and leaf blades, and the roots were well formed. There were 3 to 7 roots per plantlet, whose length increased the longer they remained in the culture medium.
After 30 days, the plantlets were transferred from acclimatisation to container pots in the greenhouse, where they remain on the benches until they reach a height of 10 cm. The conditions in the greenhouse are partially controlled and include watering and nutrition, heating and cooling, as well as meticulous plant material protection. Survival ranged from 70 to 90% after acclimatisation, depending on the clone variability.