Phenolics are believed to inhibit the shoot formation in magnolia in vitro. The aim of this study was to determine the influence of sucrose, nitrogen salts and cytokinin concentrations on the phenolics content in relation to shoot formation in Magnolia × soulangiana ‘Coates’ in vitro. The results showed that the concentration and ratios of benzylaminopurine (BAP), sucrose and nitrogen salts in the Murashige and Skoog (MS) medium had a significant effect on the leaf and axillary shoot formation as well as on the phenolics content. The highest multiplication rate (4.8 shoots/explant) and shoots of good quality were obtained on medium containing 0.2 mg·dm^-3 BAP, 100% nitrogen salts in relation to the MS medium and 20 g·dm^-3 sucrose. At this sucrose level, increasing BAP concentration from 0.2 to 1.0 mg·dm^-3 resulted in the inhibition or slight stimulation of shoot formation depending on the nitrogen levels (100 and 75/50%, respectively). At low sucrose-to-nitrogen ratio in the medium, increased BAP levels induced the leaf browning. The highest inhibition of M. × soulangiana ‘Coates’ shoot formation has been observed on medium containing 30 g·dm^-3 sucrose, reduced nitrogen salts levels and BAP at concentration 1.0 mg·dm^-3. A medium with a high sucrose-to-nitrogen ratio stimulated also phenolics production in magnolia shoots. The addition of BAP lowered phenolics production compared with the control medium. At high sucrose-to-nitrogen ratio, increasing BAP levels significantly stimulated phenolics production. The results of the study showed that not in all the treatments did the enhanced phenolics levels in the shoots of M. × soulangiana ‘Coates’ coincide with decreased shoot formation.

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