This study assesses the effect of meta-topolin (mT), an aromatic natural cytokinin, on micropropagation of pear rootstock OHF-333 (Pyrus сommunis L.). Cultures were incubated in a growth chamber under controlled conditions. An in vitro culture was maintained on a modified culture medium Murashige and Skoog [1962] supplemented with meta-topolin (0 μM, 3 μM, 6 μM, 9 μM or 12 μM). After three weeks’ growth the parameters and the physiological and biochemical analysis were investigated. The results of this study suggest that the in vitro culture in the absence of cytokinins does not provide a practical solution for efficient multiplication of pear rootstocks. A good multiplication rate and high quality shoots were found at 6–9 μM mT treatment. The use of meta-topolin resulted in improvement of the leaf gas exchange and low content of phenols, as well as in the total antioxidant activity. Hence the cytokinin meta-topolin in concentrations of 6–9 μM was selected as an optimum cytokinin level in the multiplication of pear rootstock OHF-333.

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