Abstract
Living xylem ray parenchyma cells of woody plants are adapted to freezing temperatures during winter either by extracellular freezing or by freezing avoidance by deep supercooling. In this study, we studied the low temperature behaviour of xylem ray parenchyma cells of M. bombycis by observation using cryo-scanning electron microscopy and freeze-fracture replica technique in addition to differential thermal analysis (DTA). DTA of xylem in M. bombycis indicated deep supercooling profiles of xylem ray parenchyma cells both in winter and summer. But observation by cryo-scanning electron microscopy and freeze-fracture replica technique showed that xylem ray parenchyma cells in M. bombycis took a variety of low temperature behaviour ; in winter, deep supercooled cells, extracellularly frozen cells, freeze-concentrated cells and dried cells were observed, while in summer deep supercooled cells and dried cells were observed.
