RNA Metabolism in the Quiescent Centre and Neighbouring Cells in the Root Meristem of Zea mays

Abstract

Summary The rate of RNA synthesis was investigated in three regions of the root apex of Zea mays , including the quiescent centre, using 3 H-adenosine as a precursor and autoradiography of tissue sections. The rate of synthesis in the Q.C. appears to be higher than would be expected if the RNA content of its cells double during their intermitotic period. However, microdensitometry indicates that the mean RNA content of these cells is maintained at a constant level during root growth. Estimates of the rate of halving of the radioactivity in the cells of each region give no indication that the RNA detected by autoradiography is degraded once it is made. The half-times can be accounted for by the dilution of radioactivity through the action of cell division and cell growth in each region. It seems possible that estimation of the rate of RNA synthesis, at least as it normally proceeds within the Q.C., may be distorted by the feeding of a precursor.