HISTO-CYTOLOGICAL STUDY OF APICES OF COFFEE (COFFEA-RACEMOSA AND C-SESSILIFLORA) IN-VITRO PLANTLETS DURING THEIR CRYOPRESERVATION USING THEENCAPSULATION-DEHYDRATION TECHNIQUE

Apices of in vitro plantlets of Coffea racemosa and C. sessiliflora wi thstood freezing in liquid nitrogen using the encapsulation-dehydratio n technique. An intense intracellular starch accumulation was noted af ter overnight culture of apices on standard medium. Apices of C. sessi liflora required a 3 to 10-d pregrowth in liquid medium containing 0.7 5 M sucrose, whereas those of C. racemosa required a progressive incre ase of the sucrose concentration from 0.5 to 1 M. After the dehydratio n phase, cells of some apices were severely damaged, showing osmiophil ic granules on the surface of the plasmalemma. In other apices, cells were less severely damaged, showing exocytosis vesicles at the periphe ry of the plasma membrane. After freezing, survival rates of 27 and 37 % were obtained for C. racemosa and C. sessiliflora, respectively. Two growth recovery patterns were observed: direct development of foliar primordia and callusing.