IN-VITRO FLOWERING ON LONG-TERM SUBCULTURED PEAR SHOOTS

In vitro flowering was induced from long-term (for six years) subcultu red shoots of pear (Pyrus communis L.). Shoots were subcultured every 30 d on WP medium (BA 1 mg l(-1), sucrose 3%, agar 0.8%) and maintaine d for six years. Flower induction occurred when shoots were cultured o n MS medium supplemented with CPPU at 1 or 5 mg 1 and incubated at 15 degrees C for 15 or 30 d. Shoots cultured on WP medium supplemented wi th CPPU did not flower. Shoots cultured on MS or WP medium supplemente d with CPPU and maintained at 26 degrees C also did not flower. Flower ing was observed soon after the treated shoots were transferred to MS medium supplemented with BA 1 mg l(-1) and incubated at 26 degrees C. Flowering percentages were 4 to 12%. Each flower consisted of five sep als, five white petals, several stamens, and one pistil. Pollen grains were formed, but development of the ovary and ovules was incomplete.