Radial variation of wood cell dimensions in cork oak (Quercus Suber L.)

• Autores: Sofia Leal, Vicelina Sousa, Helena Pereira
• Localización: Suberwood: new challenges for the integration of cork oak forests and products / Javier Vázquez Piqué (ed. lit.), Helena Pereira (ed. lit.), María Arantzazu González Pérez (ed. lit.), 2008, ISBN 978-84-96826-47-2, págs. 403-413
• Idioma: inglés
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• Resumen

  • The variation of wood anatomy in Quercus suber L. was studied in young trees, never submitted to cork harvesting, and growing under water stress, in relation to vessel size and distribution and to biometry of libriform fibers and rays (multi and uniseriate). Vessels were measured continuously along the radial direction by image analysis, on transverse surfaces, while fiber and ray biometry was studied at three radial positions. Fiber dimensions presented an increasing radial trend, already reported for other oak species: on average, fiber length increased from 1.00 to 1.23 mm, fiber width from 15.8-19.7 to 19.6-23.3 um and wall thickness from 6.7 to 8.1 µm. Multisseriate rays reached on average 5.15 mm in height and 0.48 mm in width, while unisseriate rays had an average height of 225 um and 11 cells. The ray dimensions remained rather constant along the radius, contrary to the usual decline with age, and this was interpreted as an adaptation to improve water storage. The mean vessel area and conductive area increased from pith to bark, on average from 7767 to 21716 um2 and from 4.0 to 9.3 %. Vessel density was on average 5.7- 4.4 vessels/mm2. Cork oak trees had sraaller vessel sizes in comparison with ring-porous oak species. This feature was interpreted as an adaptation to the harsh edaphoclimatic conditions, resulting in lower rates of water conduction and lower probability of cavitation occurrence, therefore contributing to the species tolerance to water stress. The radial constancy of vessel density, not usual in other tree species, was also interpreted as a strategy to survive to water stress.