The relative RNA content in cells of different regions of root tip of Zea mays was measured cytophotometrically. Cells of quiescent center showed relatively low RNA content as compared to initials of root cap, cortex and central cylinder. With the onset of cell elongation, RNA content per cell increased and reached its peak value in fully expanded cells. IAA treatment has no effect on RNA content of meristematic cells but effectively raised the endogenous levels of RNA in alongating cells. A sharp correlation is observed between increase in RNA content and increase in cell size at different phases of elongation.
