[Changes in desiccation tolerance and cell ultrastructures of wampee axes induced by progressively raising sucrose concentration of culture medium].

The desiccation tolerance of wampee [Clausena lansium (Lour.) Skeels] axes was significantly increased when they were pre-cultured with woody plant medium with progressively increasing sucrose contents (27% --> 50% --> 60%). Most of the plumular axes could survive a moisture content as low as 18.8% and could regenerate plantlets. Results of electron microscopy showed that when the moisture content of the plumular axes of the control was brought down to 36.3%, the plasmolemma and vacuole disappeared, and the chloroplasts and mitochondria collapsed. Plate I-1-4) While plumular axes had been pre-cultured by progressive raising of sucrose concentration of culture medium and then desiccated to a moisture content of 35.8%, plasmolysis occurred in most of the cells, with dense cytoplasm and big starch grains in the chloroplast (Plate I-6-8, Plate II-9). Furthermore, after they were desiccated to a moisture content of 18.8%, severe plasmolysis was observed, most of the chloroplasts and mitochondria were partly injured (Plate II-10). The desiccative injury in cells of the plumular axes desiccated to a moisture content of 18.8% could be repaired after 4 d of rehydration (Plate II-11-16).