A STUDY ON CRYSTALLIZATION CHARACTERISTICS AND VISUALIZATION OF ONION CELLS AT DIFFERENT PRE-COOLING RATES
The formation of intracellular ice in the cell could lead to severe cell damage and many problems in cryopreservation. This paper investigated the effects of pre-cooling before ice seeding. The onion epidermal cells were pre-cooled at -1 °C/min, -5 °C/min, -10 °C/min, -20 °C/min, -50 °C/min and -80 °C/min respectively and the ice is seeded as soon as the cryostage achieved -7 °C. The high speed camera was used to observe the patterns in the location and formation of intracellular ice crystals and to evaluate the degree of cell deformation. The results showed that an increase in pre-cooling rate influenced the formation pattern of intracellular ice crystals. There are three modes of intracellular ice formation: Mode A: ice crystal first appearing in the cytoderm and spreading to another cytoderm; Mode B: ice crystal spreading toward the center after cytoderm crystallization; Mode C: ice first appearing in the inner cell and spreading to cytoderm. Finally, the growth rate and cell deformability of ice crystals were calculated and analyzed in three different processes.