Arginine decarboxylase and polyamines required for embryogenesis in the wild carrot [Daucus carota]

Embryogenic cultures of Daucus carota treated with 1 millimolar α -difluoromethylarginine, a specific inhibitor of arginine decarboxylase, exhibited nearly a 50 percent reduction in embryo formation compared with controls. Putrescine and spermidine concentrations in the treated cells were greatly reduced. Addition of putrescine, spermidine, or spermine to the culture medium restored embryogenesis in the treated cultures. Embryogenesis was not significantly affected by α -difluoromethylornithine, an inhibitor of ornithine decarboxylase. These results suggest that polyamines have a major function in plant embryo development and that the wild carrot synthesizes polyamines through the biosynthetic pathway involving arginine decarboxylase rather than ornithine decarboxylase.