The experimental work was carried out using the pear rootstock Old Home x Farmingdale OHF-333 (Pyrus communis L.) in the Plant Biotechnology Laboratory of the Fruit Growing Institute in Plovdiv, Bulgaria. All the in vitro plants were cultivated in a growth chamber ata temperature of 22±2°С and photoperiod of 16/8 hours (40 µmol m-2 s-1PPFD). The in vitro culture was sustained through a 3-week subculturing of the modified nutrient medium MS, enriched with 2,5 μM BAP or meta-topolin (mT), 0,05 μM IBA, 30 g l-1 sucrose, 6,5 g l-1 agar. For the purpose of carrying out the experiments, glass (G) and polypropylene (PP) containers (600 ml) were used.
The РР containers were equipped with a green filter enabling gas exchange with the environment. The physiological and biochemical analyses showed that the plants grown in polypropylene containers with improved gas exchange with the environment had a better physiological status compared with those grown in glass jars.