Some observations on the very rapid abscission of the petals ofGeranium robertianum L.

Abstract

The petals of young flowers ofGeranium robertianum L. start to be shed 2.25 hours after exposure to 20 ppm ethylene whilst controls kept in air take approximately 8 hours longer. The detachment of the petal takes place at its junction with the receptacle. The cells in the region show evidence of cell wall degradation and fracture takes place by loss of cell cohesion along the line of the middle lamella. The petal base is surrounded by a canal of receptacle tissues which alter shape either during or immediately after fracture. It is proposed that these structural changes may produce stresses which facilitate fracture.