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

Investigations were undertaken on the desiccation and freezing sensiti vity of recalcitrant seeds of three species: tea [Camellia sinensis (L .) O. Kuntze], cocoa (Theobroma cacao L.) and jackfruit (Arrocarpus he rerophyllus Lamk.). All species showed changes in the physiological ch aracteristics, desiccation and freezing sensitivity of both the seed a nd the embryonic axes with increasing seed maturity. Fully mature seed s of tea, cocoa and jackfruit survived desiccation to 24, 35 and 31 % moisture content, respectively, but at these moisture levels seeds wer e not able to tolerate freezing in liquid nitrogen (-194 degrees C). S ome survival of cryopreservation was, however, achieved for excised em bryonic axes of partially and fully-mature tea and jackfruit seeds aft er drying to 14% moisture content; cocoa axes were totally freezing se nsitive at all three stages of physiological maturity studied. Biochem ical investigations on fully mature axes after desiccation and freezin g showed that the decline in viability with moisture level was associa ted with increased leachate conductivity, lipid peroxidation products and/or soluble carbohydrates. Evidence for disruption of cell membrane s during desiccation and freezing was supported by ultrastructural stu dies. (C) 1995 Annals of Botany Company