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 so matic embryos, hypocotyl explants from carrot seedlings were cultured in the presence of auxin. The various tissues responded in different w ays. The external layers (epidermis, cortical parenchyma) expanded, wh ereas the provascular cells divided and expanded. Hence only the latte r cells can generate cell lines and somatic embryos. A cyto-histologic al analysis showed that pro-embryogenic masses, from which embryos dev elop in the absence of auxin, are generated from the same provascular cells which, after a proper exposure to auxin, undergo an asymmetric d ivision.