[en] The present work compares the effect of γ-radiation dose and time in culture on the growth of cambium and phloem carrot (Daucus carota) root explants. It was found that the phloem is more radiosensitive than the cambium and that both tissues were more radiosensitive when irradiated on excision at the G₁ phase rather than at the end of the lag phase on the ninth day of growth in culture when cells were predominantly at the G₂ phase. The nuclear volumes of cells from both tissues were similar but were larger at the end of the more radioresistant lag phase than those of the G₁ phase on excision. However, nuclear volume could not account for the differences in radiosensitivity between either the tissues or irradiation times in culture