ASCORBIC-ACID EFFECT ON THE ONSET OF CELL-PROLIFERATION IN PEA ROOT

The ability of ascorbic acid to induce cell proliferation of non-cycli ng cells was investigated in quiescent embryo root of Pisum sativum L. cv. Lincoln, as well as in the active plantlet root meristem, where a minor portion of the cells is non-proliferating. Quiescent embryo cel ls speeded up the G(0)-G(1) transition during germination in the prese nce of ascorbic acid. In addition, proliferating cells present in the root tip of 3-day-old plantlets, arrested at the G1/S boundary by hydr oxyurea, resumed the cycle earlier than the control, when treated with ascorbic acid. In contrast, ascorbic acid was unable to induce the pr oliferation of non-cycling cells present in the active meristem. There fore, these data suggest that the ability of ascorbic acid to induce c ell proliferation depends on the physiological status of the cell. In particular the data indicate that ascorbic acid is involved in cell pr oliferation as a factor necessary to enable already competent cells to progress through the cell cycle phases, but not as a factor able to i nduce non-competent cells to overcome proliferation arrest.