Changes in the lanthanum distribution following decapitation of the sporophytes of an aquatic fern, Marsilea drummondii A. Br

The active terminal bud and the quiescent lateral buds and corresponding nodes inserted at different levels on the main rhizome of M. drummondii were examined with the EM after in vivo feeding with lanthanum nitrate. The removal of the terminal bud has two effects. It rapidly (in 2 hours) allows the lanthanum to penetrate the lateral bud tip walls at a stage when no fine structural changes are discernable and to bind to the outer surface of the plasmalemma as it does in the active terminal bud. This study including inhibited buds and buds released from apical dominance support the view that changes in the state of the cell surface (cell wall and plasma membrane) may be a prerequisite for the resumption growth activity.