title: Perforated pit membranes in imperforate tracheary elements of some angiosperms.
abstract: OBJECTIVE
  The structure of pit membranes in angiosperms has not been fully examined and our understanding about the structure is incomplete. Therefore, this study aims to illustrate the micromorphology of pit membranes in fibres and tracheids of woody species from various families.
  
  
  METHODS
  Specimens from ten species from ten genera and eight families were prepared using two techniques and examined by field-emission scanning electron microscopy.
  
  
  RESULTS
  Interfibre pit membranes with an average diameter of <4 microm were frequently perforated or appeared to be very porous. In contrast, pit membranes in imperforate tracheary elements with distinctly bordered pits and an average diameter of >or=4 microm were homogeneous and densely packed with microfibrils. These differences were observed consistently not only among species but also within a single species in which different types of imperforate tracheary elements were present.
  
  
  CONCLUSIONS
  This study demonstrates that the structure of interfibre pit membranes differs among cell types and the differences are closely associated with the specialization of the fibre cells. It is suggested that perforated pit membranes between specialized fibres contribute to the dehydration of the fibre cells at or soon after maturation.
authors.affiliation: Laboratory of Wood Biology, Graduate School of Agriculture, Hokkaido University, Sapporo 060-8589, Japan. pirika@for.agr.hokudai.ac.jp
authors.forename: Yuzou
authors.initials: Y
authors.lastname: Sano
authors.forename: Steven
authors.initials: S
authors.lastname: Jansen
mesh_terms: D002462:Cell Membrane / Q000648:ultrastructure*; D002473:Cell Wall / Q000648:ultrastructure*; D019684:Magnoliopsida / Q000648:ultrastructure*; D008855:Microscopy, Electron, Scanning