DESCRIPTION OF SOMATIC-EMBRYO-FORMING SINGLE CELLS IN CARROT SUSPENSION-CULTURES EMPLOYING VIDEO CELL TRACKING

A cell-tracking system was established to determine the capability of individual single suspension cells of carrot (Daucus carota L.) to dev elop into somatic embryos. When immobilised in phytagel, 127 out of 30 318 single suspension cells smaller than 22 mu m in diameter develope d into a somatic embryo. Single cells present at the start of the expe riment were classified on the basis of their morphology into five grou ps: small spherical vacuolated cells; small spherical cytoplasm-rich c ells; oval vacuolated cells;elongated vacuolated cells and cells that could not be classified into either one of these groups. Single cells of all morphologically distinguishable single cell types developed int o somatic embryos with a frequency that varied between 19 and 100 soma tic embryos per 10 000 cells. This suggests that the capability of ind ividual single cells to form somatic embryos is not restricted to a pa rticular cell type distinguishable on the basis of its morphology. Thr ee major pathways were observed during development. Oval and elongated cells developed into somatic embryos via an asymmetrical cell cluster . Spherical cells developed via a symmetrical cell cluster into somati c embryos. Before formation of a somatic embryo, cells of a more varia ble initial morphology first developed aberrantly shaped cell clusters . This suggests that the developmental pathway leading to a somatic em bryo can be predicted by the initial single-cell morphology.