Abscisic acid effect on the DNA microgradients of decapped maize roots

Longitudinal and transversal total DNA gradients were analysed in 42-μm thin sections of maize root tips. The optimum DNA concentration was found in the apex (quiescent centre and meristem). It significantly increased after removal of the root cap, which can be considered an essential source of abscisic acid (ABA). When the caps were taken off and agar blocks containing ABA were immediately placed on the apical cut sections, the total DNA level in the root apex decreased greatly. ABA regulation of cellular and nuclear behaviour is discusse