title: Topochemical studies on modified lignin distribution in the xylem of Poplar (Populus spp.) after wounding.
abstract: OBJECTIVE
  Information on the influence of wounding on lignin synthesis and distribution in differentiating xylem tissue is still scarce. The present paper provides information on cell modifications with regard to wall ultrastructure and lignin distribution on cellular and subcellular levels in poplar after wounding.
  
  
  METHODS
  Xylem of Populus spp. close to a wound was collected and processed for light microscopy, transmission electron microscopy and cellular UV microspectrophotometry. Cell wall modification with respect to lignin distribution was examined at different stages of wound tissue development. Scanning UV microspectrophotometry and point measurements were used to determine the lignin distribution.
  
  
  RESULTS
  Xylem fibres within a transition zone between differentiated xylem laid down prior to wounding and the tissues formed after wounding developed distinctively thickened secondary cell walls. Those modified walls and cell corners showed, on average, a higher lignin content and an inhomogeneous lignin distribution within the individual wall layers.
  
  
  CONCLUSIONS
  The work presented shows that wounding of the xylem may induce a modified wall architecture and lignin distribution in tissues differentiating at the time of wounding. An increasing lignin content and distinctively thickened walls can contribute to improved resistance as part of the compartmentalization process.
authors.affiliation: University of Hamburg, Department of Wood Science, Division Wood Biology, Hamburg, Germany. c.frankenstein@holz.uni-hamburg.de
authors.forename: C
authors.initials: C
authors.lastname: Frankenstein
authors.forename: U
authors.initials: U
authors.lastname: Schmitt
authors.forename: G
authors.initials: G
authors.lastname: Koch
mesh_terms: D002454:Cell Differentiation; D002473:Cell Wall / Q000737:chemistry; D021621:Imaging, Three-Dimensional; D008031:Lignin / Q000032:analysis*; D046529:Microscopy, Electron, Transmission; D015591:Microspectrophotometry; D032107:Populus / Q000033:anatomy & histology / Q000737:chemistry / Q000648:ultrastructure*; D014466:Ultraviolet Rays
chemical_list: D008031:Lignin