The process of aclimatization for apple plantlets leads to the stoping of the vegetative plant growth which could last a few months. To improve plant growth of apple rootstock 'Marubakaido' during the acclimatization process, explants from in vitro culture 1.0 to 2.0 cm long were cultivated in MS medium and chilled for 0; 240; 480; 720; 960; 1200 and 1440 hours at 4±1°C in a 16 hour photoperiod at 4.2 µmoles m-2 s-1 light intensity. The experiment was carried out in a randomized complete block design, with five replications. After chilling the explants were rooted and transplanted to greenhouse conditions where their growth, internode lengths, bud number and dry matter of aerial part and roots were observed, each fifteen days, during three consecutive months. Percentage plant survival was also evaluated after a month of acclimatization. Explants treated for 720 h produced taller plants with elongated internodes which, however, affected negatively the in vitro explant aspect leading to a decrease in plant survival during acclimatization.
Malus sp.; micropropagation; dormancy; acclimatation; growth
