EARLY EVENTS IN RICE SOMATIC EMBRYOGENESIS - CHANGES IN CORTICAL MICROTUBULE DISTRIBUTION AND ORIENTATION

The changes in the microtubular pattern during the first few days of s omatic embryo induction were studied using the rice scutellum epitheli um system. A clear difference in the distribution and orientation of t he microtubules could be found as early as 12 h after culturing. In th e control treatment, the microtubules tended to congregate near the te rminal part of the cells and had an oblique to transverse orientation with respect to the long axis of the cells. In the hormone-treated exp lants, the microtubules were more evenly distributed throughout the ce lls as compared to the control treatment. The microtubules initially h ad an oblique orientation similar to the control. However, by 16 h, th e majority of microtubules were aligned parallel to the long axis of t he cells. The scutellum epithelial cells in both the control-and hormo ne-treated explants divided periclinally at about 48 h. In the control treatment, the scutellum epithelial cells gradually became vacuolated over time, while the hormone-treated explants remained densely cytopl asmic. The fluorescence staining intensity gradually declined in the c ontrol, whereas a distinct staining pattern microtubules remained in t he hormone-treated explants.