Effects of Chilling on the Ultrastructure and Net Photosynthesis of Pellia epiphylla

Thalli of Pellia epiphylla were collected frozen from nature and chilled artificially for varying lengths of time at −22 °C. The survival and recovery of this material was compared with that of the non-chilled material by performing CO2 exchange experiments. Electron microscopy was done from the chilled and hardened thalli, and clear differences were observed in the ultrastructure of these materials. The vacuoles of the hardened tissue contained fine granular material but those of the chilled tissue had large electrondense particles embedded in finer granular substance. Oil bodies had greatly changed. In the cytoplasm there were abundant lipid-like bodies resembling oil globules of oil bodies and particularly in the vacuoles there were oily-looking flecks. Chloroplasts had large starch grains and the lamellar system was somewhat disorganized. Net photosynthesis was highest with material stored for the longest time at −22 °C.