Periderm formation across the base of short lateral roots facilitated their shedding in balsam fir (Abies balsamea(L.) Mill.), white pine (Pinus strobusL.), and hemlock (Tsuga canadensis(L.) Carr.). The periderm originated either from the pericycle, in line with normal subendodermal development, or after dedifferentiation and redifferentiation of cells across existing vascular tissues near the base of senescent short roots. Consequently the short roots were either shed neatly along with the cortex of the parent roots or they were isolated by a new layer of periderm linking existing parent-root periderm, analogous to protective tissue formation beneath petiole abscission zones. Short roots were not always isolated by periderm prior to detachment, but periderm still formed at the base of the root stubs and eventually became the superficial protective layer of the root scars.
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