Apple (Malus × domestica Borkh.) scion cv. Royal Gala was used
in the experiments, as an apple cultivar often applied as model
cultivar in in vitro experiments (Dobránszki and Teixeira da Silva,
2010; Magyar-Tábori et al., 2010). 4-week-old in vitro shoots
grown previously on MS (Murashige and Skoog, 1962) proliferation
medium supplemented with 3% (w/v) sucrose, 0.7% (w/w)agar-agar, 1.0 mg l
−1 6-benzyl-adenine riboside (BAR), 0.3 mg l
−1
indole-3-butyric acid (IBA) and 0.2 mg l
−1 gibberellic acid (GA3)
were used for the experiments. Five in vitro shoots were placed vertically
in Killner jars (400 ml in volume) on 40 ml of different media
contained the same components as the proliferation medium,
except CK supply.