HIGH-PRESSURE FREEZING OF PLANT-CELLS CULTURED IN CELLULOSE MICROCAPILLARIES

A new microculturing technique for plant cells was used to meet the re quirements of high-pressure freezing (HPF). The plant cells were cultu red inside cellulose microcapillaries, providing an easy-to-handle met hod for a real in situ fixation. The high viability of the cells was d emonstrated by regenerating shoots from microcalluses cultivated by th is method. In general, the freezing quality of the high-pressure froze n samples was excellent across the whole diameter of the capillaries, as shown with ultrathin sectioned cells after freeze-substitution and embedding in Spurr's resin. In comparison with conventional chemically fixed cells, cultured under identical conditions, all membranous comp artments and organelles were more turgid and smoother after HPF. The c ytoplasm and the matrix of the organelles were more homogeneous and de nse. Thus, high-pressure freezing in combination with the microculture method described here appears to preserve the ultrastructure of chemi cally untreated plant cells close to the native state.