Scanning Electron Microscopy of in Vitro-cultured Liquidambar styraciflua Plantlets during Acclimatization

Abstract

The acclimatization or hardening-off of in vitro -cultured sweetgum ( Liquidambar styraciflua L.) plantlets was studied using scanning electron microscopy. Comparisons were made among leaves of plantlets differentiated in culture, plantlets acclimatized after transfer from in vitro conditions, greenhouse seedlings, and mature trees. Leaves of plantlets directly from tissue culture had superficial, circular stomata and epidermal cells with irregular, sinuous undulations in the anticlinal walls. Leaves from acclimatized plantlets had ellipsoid, depressed stomata and irregularly shaped epidermal cells. Seedling and field-grown leaves had depressed, ellipsoid stomata and well-defined isodiametric epidermal cells. Stomata in all cases were confined to the abaxial surface, with densities significantly greater in leaves of in vitro plantlets than in acclimatized plantlets or greenhouse-grown plants. Epicuticular wax was generally smooth and absent of waxy outgrowths in all conditions.