title: Lignification and cell wall thickening in nodes of Phyllostachys viridiglaucescens and Phyllostachys nigra.
abstract: OBJECTIVE
  Bamboos are among the most important plants in the world. The anatomical structure and mechanical properties of the culm internode are well documented. Fewer details are available of the culm node. The aim of this study was a topochemical investigation on lignification and cell wall thickening in developing and maturing bamboo nodes. The deposition sequence and distribution of lignin structural units and cell wall thickening in different anatomical regions of the node of Phyllostachys viridiglaucescens and Phyllostachys nigra are discussed.
  
  
  METHODS
  Cell wall thickening and lignification are investigated in the outer part of the nodal region and in the diaphragm of developing and maturing P. nigra culms and in maturing culms of P. viridiglaucescens of different age classes. The lignification during ageing was studied topochemically by means of cellular UV microspectrophotometry. A combination of light microscopy and image analysis techniques were used to measure cell wall thickness.
  
  
  RESULTS
  The fibre and parenchyma cell wall thickness does not significantly increase during ageing. In the diaphragm, the cell walls are thinner and the cell diameter is larger than in the outer part of the node. In shoots, the lignin content in the epidermis, hypodermis and in both fibre and parenchyma cells of the diaphragm is relatively low compared with older culms. The fibre and parenchyma cells of the diaphragm have higher values of p-coumaric and ferulic acids than fibre and parenchyma cells of the outer part of the node.
  
  
  CONCLUSIONS
  It was hypothesized that the combination of more hydroxycinnamic acids and of thinner cell walls in combination with higher cell diameters (lower density and lower stiffness) in the diaphragm than in the outer part of the node may play an important role in the biomechanical function of the node by acting as a spring-like joint to support the culm by bending forces.
authors.affiliation: Ghent University, Laboratory of Biology, Research Group Spermatophytes, K.L. Ledeganckstraat 35, B-9000 Gent, Belgium. Bieke.Lybeer@UGent.be
authors.forename: Bieke
authors.initials: B
authors.lastname: Lybeer
authors.forename: Gerald
authors.initials: G
authors.lastname: Koch
authors.forename: Joris
authors.initials: J
authors.lastname: VAN Acker
authors.forename: Paul
authors.initials: P
authors.lastname: Goetghebeur
mesh_terms: D002473:Cell Wall / Q000502:physiology*; D008031:Lignin / Q000378:metabolism*; D015591:Microspectrophotometry; D018520:Plant Shoots / Q000033:anatomy & histology; D006109:Poaceae / Q000033:anatomy & histology / Q000502:physiology*; D013056:Spectrophotometry, Ultraviolet
chemical_list: D008031:Lignin