Reorganization of Root Apices after Irradiation

Roots were irradiated with X-rays and then fed with (8-C14) adenine at various intervals afterwards to see the effect of the radiation on the sites of DNA synthesis and hence on the behaviour of the meristem. The dividing cells of the meristem may be so badly damaged by the X-rays that they stop synthesizing DNA and dividing. When this happens the root may continue to grow by forming a new meristem. This often arises in the quiescent centre whose cells normally do not synthesize DNA or divide. These therefore form a reservoir of cells which are less vulnerable because of their quiescence, but are able to restart DNA synthesis and division when the normally meristematic cells stop. Because of this reorganization of the apex, it is not legitimate to argue about the behaviour of normal root meristems from chimeras induced by irradiation.