All wood is produced by the vascular cambium. Variability in wood properties is caused by variability in structure, reflected in differences in wood anatomy and in the structure cell walls, particularly the walls of fibres and tracheids. Although the wood anatomy of a particular species is genetically determined and predictable in a tree growing under benign conditions, this does not prevent variation being imposed to some extent by environmental stress. The structure and composition of fibre and tracheid walls may be similarly altered depending on growing conditions. In hardwoods, anatomical variation reflects such things as a change in the proportions of cell types produced by the cambium and in the amount of growth undergone by the derivatives before their final dimensions are fixed by secondary wall formation. Variation in secondary wall structure is manifested as changes in the pattern of deposition and the composition of cell wall components such as lignin and cellulose.
It is therefore self-evident that understanding the behaviour of the cambium and the development of its derivatives holds the key to understanding at least some of the processes of wood formation and how these affect the structure and quality of wood produced. One approach to this problem, dating back to the seventeenth century but still relevant today, has been the use of microscopy to investigate the fine structure of the vascular cambium and its xylem derivatives. This lecture will consider what microscopy has revealed about the structure of the cambium; the differences between dormant and active cambium and the changes taking place on reactivation at the start of the growing season; the structure of developing xylem elements, and the role of plasmodesmata and the symplasm in differentiation.
John R. Barnett is Professor Emeritus in Structural Botany in the School of Biological Sciences at the University of Reading. He obtained his BSc in Biological Chemistry at the University of Manchester in 1966, and his PhD in Biophysics under the supervision of R.D.Preston FRS, FIAWS, at the University of Leeds in 1969. From 1969 to 1977, he was employed as Scientist at the Forest Research Institute of the New Zealand Forest Service. In 1977, he took up the post of Electron Microscopist, then Director of Structural Studies in the Plant Science Laboratories at the University of Reading. In 1996 he was appointed Head of the Department of Botany, and in 2002, Head of the School of Plant Sciences.
His research interests have centred on the application of microscopy to the vascular cambium and developing secondary xylem in softwoods and hardwoods, and to developing graft unions in woody plants. He has supervised 25 PhD students in these topics and others ranging from plant anatomy to fuelwood production. He has published more than a hundred refereed papers and reports, and made more than 50 oral conference presentations.
He was elected fellow of IAWS in 1995 and Vice President in 1999, becoming President in 2002. He is a Fellow of the Linnean Society and was elected a Trustee and Council Member of the Society in 2004. He was awarded an Erskine Fellowship by the University of Canterbury New Zealand in 2005. He has served on the editorial board of the Journal of the International Association of Wood Anatomists, and is presently co-editor of Wood Science and Technology and serves on the editorial boards of Annals of Botany, Holzforschung, Sylva Fennica, and Chinese Forestry Science and Technology. In 1996 he won a major grant from the European Commission to co-ordinate and international project on the vascular cambium. He currently acts as Chair of an EC COST Action entitled Cell Wall Macromolecules and Reaction Wood, which involves coordinating scientists from fifteen European countries.