prilagođeno pretraživanje po punom tekstu

ŠUMARSKI LIST 5-6/2016 str. 70     <-- 70 -->        PDF

exceptionally vigour plants with nicely formed leaf blades, without additional callus formations and without the occurrence of vitrified plants. The plants were 1.5 to 3 cm tall and the internodes were adequately arranged. The multiplication rate was 1 at a concentration of 1 and 2 mg/L, whereas it amounted to 2.5 at a concentration of 4 mg/L. The formed plants achieved 100% in vitro rooting later on. These kinetin concentrations did not interrupt apical dominance and did not stimulate the formation of axillary shoots regardless of the duration of multiplication. The plantlets in the culture medium experienced the most intensive growth in the first 14 days of subcultivation, but subsequently started to loos their juvenile appearance.The application of the cytokinin BAP in the in vitro multiplication phase of wild cherry resulted in the formation of shoot clusters with several axillary shoots, depending on the used concentration and on clonal origin. Concentrations of 0.5 mg/L BAP resulted in morphologically regular shoot clusters with 2-3 axillary shoots, 1.5-2.0 cm tall, with no callus at the base, without any vitrification and with regularly formed internodes and leaf blades. A concentration of 1.0 mg/L BAP proved to be the most efficient. Properly shaped clusters with visible interruption of apical dominance and with new axillary shoots. The internodes were of normal appearance, the leaf blades were of exemplary size, and the colour was natural green with very little formation of unidentified callus at the base of the shoot clusters. The shoot clusters retained their juvenile appearance up to the 27th day of subcultivation, when they were transferred to fresh culture medium. The highest multiplication rate was recorded at a concentration of 1.5 mg/L BAP but with a lower microplant quality. The clusters turned yellowish in colour, the leaves and stems became brittle and the internodes were short. The newly formed axillary shoots ranged between 0.7 and 1.2 cm in height after 28 days of subcultivation, and occurred in all the axiles. A small callus growth was noticed at the base of the clusters. The shoots were fragile and broke during the excision process. A concentration of 2 mg/L BAP led to decreased multiplication and increased callus formation at the base of the clusters. The leaves were irregularly developed. Older leaves had partially increased and disproportionate leaf blades in relation to the shoots. The axillary shoots in the leaf axils were shorter and, although rare, the tips of the newly formed shoots were vitrified as a result of high BAP concentrations.The use of the cytokinin 2iP in concentrations of 5 and 10 mg/L did not stimulate multiplication, and concentration of 5 mg/L did not initiate the growth of the cultured explants. The plants remained undeveloped and had small yellowish tips. At a concentration of 10 mg/L 2iP the plants grew well and retained their green colour, but there was no multiplication or callus formation.
Drawing on the results of favourable effects of kinetin on plant height growth and the role of BAP in interrupting apical dominance and forming numerous axillary shoots, BAP and kinetin were combined in the culture medium with the purpose of establishing a production model for in vitro mass propagation of wild cherry. A BAP concentration of 1.0 mg/L was used, which yielded the best results when supplemented with 0.5 mg/L of kinetin. A combination of different concentrations of growth regulators stressed their importance in the stage of wild cherry multiplication. In spite of identical composition of culture media in all the experiments and of clonal origin of the explants, accurately determined and very large differences occurred in the morphological appearance of the shoot clusters, in the colour, firmness/juvenility of the material, and in the number of newly formed shoots. This selection eventually resulted in shoot clusters of natural appearance, with regularly formed internodes, a multiplication rate of 3-9 in dependence of clonal origin, and the duration of subcultivation of 22 to 27 days. The auxin IAA in a concentration of 0.5 mg/L was present in the culture media for wild cherry multiplication in all the tests.
The composition of all culture media satisfied the requirements of young plants at all stages. Regardless of their clonal origin, the plants were morphologically well developed and luscious, and vitrification occurred only as a result of high BAP concentrations. The selected culture media and the selected combination of growth regulators in the multiplication stage proved efficient for all the 23 clones of wild cherry. For mass production of only one clone or a selected clone group, slight modifications of cytokinin concentrations produce maximal multiplication. Namely, shoot clusters