title: Intervessel pit structure and histochemistry of two mangrove species as revealed by cellular UV microspectrophotometry and electron microscopy: intraspecific variation and functional significance.
abstract: Intervessel pits play a key role in trees' water transport, lying at the base of drought-induced embolism, and in the regulation of hydraulic conductivity via hydrogels bordering pit canals. Recently, their microstructure has been the focus of numerous studies, but the considerable variation, even within species and the histochemistry of pit membranes, remains largely unexplained. In the present study, intervessel pits of the outermost wood were examined for Avicennia marina, of dry and rainy season wood separately for Rhizophora mucronata. The thickness of the pit membranes was measured on transmission electron micrographs while their topochemical nature was also analyzed via cellular UV microspectrophotometry. Pit membranes of R. mucronata were slightly thicker in dry season wood than in rainy season wood, but their spectra showed for both seasons a lignin and a yet unidentified higher wavelength absorbing component. It was suggested to be a derivative of the deposits, regularly filling pit canals. The vestures of A. marina chemically resembled pit membranes rather than cell walls.
authors.affiliation: Royal Museum for Central Africa, Laboratory for Wood Biology and Xylarium, Leuvensesteenweg 13, 3080 Tervuren, Belgium. nschmitz@vub.ac.be
authors.forename: Nele
authors.initials: N
authors.lastname: Schmitz
authors.forename: Gerald
authors.initials: G
authors.lastname: Koch
authors.forename: Uwe
authors.initials: U
authors.lastname: Schmitt
authors.forename: Hans
authors.initials: H
authors.lastname: Beeckman
authors.forename: Nico
authors.initials: N
authors.lastname: Koedam
mesh_terms: D032407:Avicennia / Q000737:chemistry / Q000502:physiology / Q000648:ultrastructure*; D003034:Coated Pits, Cell-Membrane / Q000502:physiology / Q000648:ultrastructure*; D006651:Histocytochemistry; D046529:Microscopy, Electron, Transmission; D015591:Microspectrophotometry; D043982:Rhizophoraceae / Q000737:chemistry / Q000502:physiology / Q000648:ultrastructure*; D013056:Spectrophotometry, Ultraviolet