Air exchange rate affects the in vitro developed leaf cuticle of carnation

The leaf surfaces of Dianthus caryophyllus plants cultured in vitro in eith er airtight or ventilated vessels were examined using scanning electron mic roscopy (SEM). The resultant hyperhydrated, non-hyperhydrated and acclimati zed plants were compared for stomatal density, cuticular wax development an d stomatal function. The leaf surfaces of in vitro cultured plants were bas ically the same as those of acclimatized plants but less wax deposition was observed on their leaves. Stomata were found both open or closed after tra nsfer of plants ex vitro. However, stomata of in vitro leaves grown in vent ilated culture vessels were more functional than plants grown in other cond itions. Acclimatized plants had a normal leaf epidermal surface, and were w holly covered with waxes; their stomatal density being similar to that of h ighly ventilated plants but lower than that of less ventilated plants. Leav es of plants grown in airtight culture vessels or under a law number of air exchanges per hour had less waxes than plants grown at a higher number of air exchanges per hour or than acclimatized plants. In contrast, hyperhydra ted plants had abnormal, malformed stomata and no wax deposition was detect ed. The adaxial surface of non-hyperhydrated leaves seemed more normal than the abaxial, especially in the most ventilated vessels, and this may be du e to the former receiving more light and so developing in a more favourable microenvironment. (C) 2001 Elsevier Science B.V. All rights reserved.