Studies on the origin of totipotent cells in explants of Daucus carota L

In an attempt to identify the origin of cells capable of generating somatic embryos, hypocotyl explants from carrot seedlings were cultured in the presence of auxin. The various tissues responded in different ways. The external layers (epidermis, cortical parenchyma) expanded, whereas the provascular cells divided and expanded. Hence only the latter cells can generate cell lines and somatic embryos. A cyto-histological analysis showed that pro-embryogenic masses, from which embryos develop in the absence of auxin, are generated from the same provascular cells which, after a proper exposure to auxin, undergo an asymmetric division.