Cryofixation reveals uniqueness of reddish-purple sequent periderm and equivalence between brown first and brown sequent periderms of three conifers

摘要

Three types of periderms, brown first periderm (bfp), reddish-purple sequent periderm (rsp), and brown sequent periderm (bsp) were distinguished inAbies amabilis, Abies grandis, andTsuga heterophylla. The distinctions are based on 15 characteristics revealed largely by extension of a new cryofixation technique with various modes of illumination. On the bases of bright-yellow and pale-blue fluorescent substances in phellem cells, bright-yellow fluorescent substances in phellem walls, distinctive chemical nature of the pigments, presence of phellogen activity marker cells, and specificity of the site of occurrence next to rhytidome and several other cryofixation characteristics, rsp is established not only as distinctly different from bfp and bsp, but also as unique. Both bfp and bsp were found to be similar in all 15 characteristics, revealed by cryofixation and other techniques and thus may have similar physiological roles. This similarity implicates the incompleteness of the term first periderm.