Empirical investigations into the tunica structuring point of the shoot apex of Pelargonium zonale

A tunica structuring point of 3.85 cell units was formally predicted for th e shoot apex. This point is decisive for the genesis of the tunica corpus s tructure as such and for the number of tunica layers in an apex at any give n moment. Here, a method to determine, in empirical investigations, the the oretical number of tunica layers in real apices is demonstrated. Furthermor e. results of an empirical investigation into the postulated tunica structu ring point are presented and causes for deviations of the observed values f rom the theoretical values are discussed. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.