EFFECTS OF MEDIA OSMOTIC AGENTS ON THE GROWTH AND MORPHOGENESIS OF ACTINIDIA-DELICIOSA CV HAYWARD CALLUS

The influence of various osmotic agents (carbohydrates) on the morphog enesis and growth of callus of Actinidia deliciosa cv Hayward was stud ied. Sucrose supported the highest level of growth and the lowest was supported by the sugar alcohols used in the experiments (glycerol, man nitol, sorbitol). The growth and survival of callus were evaluated wit h different osmotic sources in media containing glycerol, mannitol, or sorbitol at a concentration of 0.2 M each for an extended period of e ight subcultures (360 days). Two crucial points were identified: until the third subculture (135 days) the vitality seemed to be elevated; w hereas the fifth (225 days) seemed to be a ''point of no return'' for tissues grown in glycerol and mannitol. Pretreatment with osmotic carb ohydrates was shown to increase the magnitude of the morphogenetic eve nts of callus subsequently transferred to sucrose-containing medium. C allus grown in the presence of mannitol and sorbitol showed a similar frequency of morphogenetic response. With respect to the media contain ing glycerol and sucrose, these induced more intense regeneration of s hoots. When glycerol was present in the medium, however, we observed a synchronization of the morphogenetic response. Our results suggest th at it is possible both to stimulate and to synchronize morphogenesis u tilizing osmotic conditioning subcultures.