EFFECT OF CULTURE VESSELS SIZE AND COVERING MATERIAL ON LEAF MORPHOLOGICAL AND ANATOMICAL CHARACTERISTICS OF QUERCUS EUBOICA IN VITRO PLANTLETS

Quercus euboica Pap., a rare, endangered oak species of Greece can be used as an ornamental plant in urban and suburban landscapes. Its drought tolerance and capability to sprout again after fire and grazing makes it a suggested species for reforestation in Mediterranean climates. The effect of different types of culture vessel covers on morphological and anatomical characteristics of leaves of in vitro grown plantlets was studied. Glass culture vessels of 300, 180 and 100 ml volume were used and covered with plastic wrap, magenta caps, semi hard plastic film, metallic caps or plastic caps. The use of different types of culture vessel covers influenced the gaseous environment and the relative humidity inside the culture vessels, which affected the morphological and anatomical characteristics of the leaves of microshoots that developed. Semi hard plastic film, as well as metallic and plastic caps induced high relative humidity and different gases concentrations compared to plastic wrap and magenta caps. Semi hard plastic film and metallic or plastic caps led to the production of shoots with big hyperhydrated leaves and big spherical stomata having difficulty in closing, which led to quick dehydration at ex vitro transfer of the plantlets and low survival during the stage of acclimatization. Plastic wrap and magenta caps induced the formation of leaves with smaller and more elliptical stomata similar to stomata of ex vitro formed leaves. In vessels covered with plastic wrap and less in those covered with magenta caps a gradual dehydration of the medium was observed. Finally, differences on the number and anatomy of trichomes in the abaxial surface of in vitro leaves were observed compared to ex vitro leaves.