Abscission Zone Anatomy, Development, and Separation in Nicotiana tabacum

Anatomical differences between Lizard\u27s Tail and Little Turkish varieties of Nicotiana tabacum which exist during development of the separation zone and as floral abscission occurs are described. Cells are larger in Little Turkish by an average of 5 to 6 microns in the abscission zone and by 10 microns in the developing fruit. The separation layer in Little Turkish is located 5 to 7 tiers of cells distal to the groove and is usually composed of only 4 to 6 tiers. In Lizard\u27s Tail the separation layer is 8 to 12 tiers distal to the groove, and as many as 50 tiers of cells may be involved. Although there is a seasonal variation in the time required for the completion of the separation reactions, the process involves several additional days in Little Turkish. In both varieties abscission seems to occur as a result of the dissolution of the middle lamella. The cellulose walls appear to be unchanged after the completion of abscission