LOCALIZATION OF CALCIUM DURING SOMATIC EMBRYOGENESIS OF CARROT (DAUCUS-CAROTA L)

The distribution of free cytosolic Ca2+ was studied during somatic emb ryogenesis of carrot using confocal scanning laser microscopy with flu o-3 as a fluorescent Ca2+ indicator. Chlorotetracycline fluorescence, antimonate precipitation and proton induced X-ray emission analysis we re used as additional methods to confirm the results obtained with flu o-3. The process of embryogenesis was found to coincide with a rise in the level of free cytosolic Ca2+. The level of Ca2+ was low in proemb ryogenic masses and relatively high in later stages of embryogenesis. The highest signal was found in the protoderm of embryos from the late globular to the torpedo-shaped stage. A gradient in fluorescence inte nsity was often observed along the longitudinal axis of the embryos. T he most conspicuous intracellular signal was found in the nucleus. Oth er organelles did not take up the dye and were always without fluoresc ence. The changes in [Ca2+](c) are discussed in relation to physiologi cal processes which are known to be important during somatic embryogen esis.