Critical pore sizes affecting fluid penetration in sycamore wood / Basilio Frasco Vianez.

Tese (mestre) - University College of North Wales, 1986

Scanning electron microscopy ( S.E.M.) and physical tests were used on twig and stem wood of Sycamore (Acerpseudoplatanus) to determine the critical pore radii within and between vessel systems. The main results of the study summarised as follows: 1 - In both twig and steem wood of Sycamore, almost all the intervessel pit membranes were absent, while vessel-fibre and vessel-ray parenchyma pit membranes were always intact. 2 - Plugs with fibrillar structure were found blocking some vessels. 3 - Finite maximum vessel system lengths of 15 cm for twig wood and 31 cm for stem wood were obtained. 4 - For specimens longer than the maximum vessel system tength, the maximum effective pore radii for both twig and stem wood were 0.6µm. It was concluded that: 1 - The absence of intervessel pit membranes does not seem to be artefactual. 2 - If the absence of the intervessel pit membrane is a characteristic of Sycamore, it is clear from the physical test results that the pit apertures are not the critical pores determinisg vessel system length. 3- There are two hypotheses about the way in which vessel system endings might be defined: either, all vessels interlinked by membrane-less bordered pits must eventually and simultaneously terminate with an element which is imperforate at one and with all the intervessel pit membranes present and containing small pores; or, all vessel systems interlinked by membrane-less intervessel pits might be blocked by fibrous plugs, again at a particular length. .