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Wood1 (04-Mar-03)


Nomenclatural principles III & IV - see also Summary Comments on the International Code of Botanical Nomenclature by James Reveal (watch out for typos - NT).

This is wood...

 

Wood is secondary xylem, that is xylem that develops from a vascular cambium, rather than by differentiation of the procambial derivatives of an apical meristem.

Pinus cookie - Multimedia Toolkit... © 2000 University of Wisconsin Board of Regents

 

 

...and so is this. Note the annual rings in these temperate zone woods, and note the conspicuous rays. Also note the three planes in which this cookie is sliced:

Quercus cookie - Multimedia Toolkit... © 2000 University of Wisconsin Board of Regents

Transverse,

 

Radial,

and Tangential.

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Acer stem. Photo N. G. Dengler, © 1998 Botany Department, University of Toronto.

In transverse section the water-carrying pipes (tracheids, vessels) that run up and down in woody stems appear as as small and large circles, respectively.


Acer stem. Photo N. G. Dengler, © 1998 Botany Department, University of Toronto.

In radial section we can see the rays (horizontally oriented cells across the lower portion of the image), and we get an idea of how the vessels act as pipes to carry water from the roots to the canopy.


Acer stem. Photo N. G. Dengler, © 1998 Botany Department, University of Toronto.

In tangential section we are slicing at right angles to the rays, and so can see how they are built up from one or more vertical files of cells.

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Some more images of wood development and structure...


Robinia vascular cambium in tangential section. Photo N. G. Dengler, © 1998 Botany Department, University of Toronto.

Pinus tracheids. Photo N. G. Dengler, © 1998 Botany Department, University of Toronto.

Magnolia vessel and fibers. Photo N. G. Dengler, © 1998 Botany Department, University of Toronto.

Acer vessel and fibers. Photo N. G. Dengler, © 1998 Botany Department, University of Toronto.


Digitization of all but the first two photos on this page made possible by a University of Toronto Faculty of Arts and Science Instructional Initiative Grant (FY 1998/99) to Nancy Dengler, Tim Dickinson, Tammy Sage Department of Botany. Digitization carried out by: Julie Kang, Summer 1998.

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Further reading

Judd et al. (2002), Chapter 4 - p. 82.

More about wood

Sporne, K. R. (1978). The morphology of Angiosperms. New York, St. Martin's Press.

Instructional Resouces (BotIT) - University of Wisconsin - Madison, Department of Botany


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Please send your comments to tim.dickinson@utoronto.ca; last updated 04-Mar-2003