DESICCATION AND FREEZING SENSITIVITY IN RECALCITRANT SEEDS OF TEA, COCOA AND JACKFRUIT

Investigations were undertaken on the desiccation and freezing sensitivity of recalcitrant seeds of three species: tea [Camellia sinensis (L.) O. Kuntze], cocoa (Theobroma cacao L.) and jackfruit (Arrocarpus hererophyllus Lamk.). All species showed changes in the physiological characteristics, desiccation and freezing sensitivity of both the seed and the embryonic axes with increasing seed maturity. Fully mature seeds of tea, cocoa and jackfruit survived desiccation to 24, 35 and 31 % moisture content, respectively, but at these moisture levels seeds were not able to tolerate freezing in liquid nitrogen (-194 degrees C). Some survival of cryopreservation was, however, achieved for excised embryonic axes of partially and fully-mature tea and jackfruit seeds after drying to 14% moisture content; cocoa axes were totally freezing sensitive at all three stages of physiological maturity studied. Biochemical investigations on fully mature axes after desiccation and freezing showed that the decline in viability with moisture level was associated with increased leachate conductivity, lipid peroxidation products and/or soluble carbohydrates. Evidence for disruption of cell membranes during desiccation and freezing was supported by ultrastructural studies. (C) 1995 Annals of Botany Company