Occurrence of tension wood in two mangrove species and its effect on selected wood anatomical properties
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ORIGINAL ARTICLE
Occurrence of tension wood in two mangrove species and its effect on selected wood anatomical properties S. Shashikala1 • M. Krupa1 • M. Sujatha1 • Jean Simon1
Received: 7 February 2020 / Accepted: 28 August 2020 Ó Indian Academy of Wood Science 2020
Abstract The aim of the study is to characterise the cellular structures in tension wood and compare its effect on the selected anatomical parameters in two mangrove wood species viz. Excoecaria agallocha Linn. and Sonneratia caseolaris (L.) Engl. Wood blocks of 1 cm3 were prepared and thin sections of cross sections were cut using microtome and stained with Azure II to differentiate the structure of normal wood from tension wood fibres. The anatomical parameters analysed in this present study were vessel frequency, tangential vessel diameter and fibre wall thickness in tension wood as well as in normal wood. Vessel diameter and vessel frequency were significantly lower in tension wood compared to the normal wood in both the species. The reduction of tangential diameter in tension wood region is a way of protecting these elements from cavitation and providing mechanical support for the plant than liquid transport. A significant variation in fibre wall thickness was observed between tension wood and normal wood in both species. Keywords Mangroves Fibre wall thickness Tangential vessel diameter Tension wood Vessel frequency
Introduction Gelatinous fibres (g-fibres) are often produced in plant organs in response to external forces like gravity, wind and function in maintaining plant architecture (Wardrop 1964; & S. Shashikala [email protected] 1
Institute of Wood Science and Technology, Bangalore, Karnataka, India
Wilson and Archer 1977; Fisher and Stevenson 1981; Fisher and Blanco 2014). In many species, the tension wood is characterised by the presence of gelatinous fibres. Tension wood region has different characteristics due to which non-uniform effects on wood properties occur. Nonuniform shrinkage due to decreased dimensional stability poses problem like warping. These gelatinous fibres are produced mostly in leaning or displaced dicotyledonous stems (Fisher 1985) and are associated with increased tension forces in the wood (Bamber 2001), movement of stress back to their normal orientation (Fisher and Stevenson 1981). In general, the tension wood occurs in a tree with eccentric growth which can be a result of increased duration of cell division and this can result in either increase or decrease in the anatomical properties such as fibre length, wall thickness, vessel frequency and vessel diameter. Anatomically, tension wood is closer textured than normal wood. It tends to have fewer vessels of smaller diameter than usual and a greater proportion of fibres, which may be abnormally thick walled. Its important diagnostic feature, however, is the presence of gelatinous fibres, also known as tension wood fibres. Jourez (1997) considers tension wood as a complex physiological phenomenon, varies from species to species where there is an i
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