Tyloses in abscission scars of loblolly pine

During a study of fascicle abscission in Pinus taeda L., tyloses were obser ved to occlude tracheids of both proximal and distal abscission scars. The tyloses represent the protrusion of ray parenchyma cells into tracheid lume ns. Multiple tyloses often arise from a given parenchyma cell and can enter multiple tracheids. Tyloses occur as part of an abscission process that al so includes the presence of Type II cells (programmed to enlarge during abs cission in the presence of ethylene) and rupture of tracheids-features comm on to abscission in angiosperms.