Abstract Detail

100 years of Baileyan Trends – Wood Evolution, Function and Future

Wheeler, Elisabeth [1], Baas, Pieter [2].

Baileyan Trends and the Fossil Record.

Bailey & Tupper's classic 1918 paper on size variation in tracheary cells in vascular plants proposed a bidirectional transformation series from tracheids to vessel elements and from tracheids to libriform fibers, reflecting a “division of labor” for conductance and support. Their classic illustration (Fig. 6) summarizes their ideas for changes in 1) vessel elements, from relatively long and narrow with scalariform perforation plates and scalariform-opposite intervessel pits to shorter vessel elements with simple perforation plates and alternate intervessel pits, and 2) fibers, with a reduction in size and number of pits. Subsequently, Frost (1930) elaborated on trends in perforation plates and intervessel pitting, and Kribs (1935) proposed “lines of specialization” for rays and axial parenchyma, based on correlations with vessel element features. In 1991, we examined the fossil record of dicotyledonous wood and found general support for these Baileyan trends. Because of additional information about fossil angiosperm woods accumulated over the last 25 years, we re-examined the fossil wood record to look at incidences of wood anatomical features through geologic time. Features examined were vessel element length, perforation plates, intervessel pitting, ray type and axial parenchyma distribution, and ring-porosity, which, in 1924, Bailey described as a specialized feature “closely associated with the acquisition of a pronounced resting period and … a deciduous habit.” Data used come from the InsideWood web site. At temperate latitudes (Laurasia and high latitude Gondwana), an epoch by epoch time series supports the Baileyan transformation series; “primitive” features such as scalariform perforations, apotracheal diffuse parenchyma and heterocellular rays are common in the Cretaceous and become much less frequent in the Cenozoic (especially post-Eocene). In contrast, in the paleotropics, each epoch has an equally “modern” spectrum of wood anatomical features. In Laurasia (North America, Europe, temperate Asia), ring porosity occurs at low levels in the Cretaceous and Paleogene and reaches modern levels in the Miocene. In the tropics, there is a low incidence of ring porosity and helical thickenings throughout all epochs. We suggest that tropical conditions have accelerated xylem evolution towards greater hydraulic efficiency (selection for simple perforations), biological defense and hydraulic repair (elaborate paratracheal parenchyma patterns).

Related Links:
InsideWood - wood anatomy web site

1 - N.C. State University, Forest Biomaterials, Raleigh, NC, 27695-8005, USA
2 - Emeritus Professor Of Systematic Botany, PO Box 9514, Leiden, 2300 RA, Netherlands

Wood anatomy
functional traits.

Presentation Type: Colloquium Presentations
Number: 0003
Abstract ID:602
Candidate for Awards:None

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