DOI: 10.5061/dryad.hx3ffbgb4
title: Wood anatomy of Indian oaks, with reference to systematic, ecological and evolutionary perspectives

description: The present study provides a comprehensive wood microstructure analysis of
 16 species of the genus Quercus inhabiting the Himalayan region of India.
 Indian oaks can be categorised into two groups: Ring porous oaks and
 diffuse porous oaks. Most of the diffuse porous oaks were quite homogenous
 in their microstructure and showed slight variations in ray cellular
 composition and axial parenchyma distribution. The results revealed that
 the current classification of Quercus is not in concordance with the wood
 microstructure. From an ecological view point, cluster analysis gave
 interesting results; largely suggesting that quantitative wood
 microstructure of Indian oaks is governed by different environmental
 conditions of eastern and western Himalayas. The genus is also examined
 from evolutionary point of view. All the species of oaks showed a
 combination of both primitive and advanced wood anatomical characters.
description: Wood
 anatomical features were examined using compound microscope from the
 permanent slides and macerated samples. The average tangential diameter of
 vessels was determined from twenty-five measurements taken from transverse
 section. The frequency of vessels was determined from the average of
 twenty counts per mm<sup>2</sup> area. Ten counts were taken
 for the size of intervessel pits from longitudinal section. The rays per
 mm is based on an average of ten counts in one mm area in tangential
 section. Ray height and ray width was based on twenty counts, determined
 from tangential sections. From the macerated material, fibre and vessel
 dimensions viz. fibre length, fibre diameter, fibre lumen diameter, fibre
 wall thickness and vessel length were taken. Twenty-five measurements were
 taken for fibre characteristics while ten measurements were taken for
 vessel characteristics. For wood anatomical descriptions, the terminology
 given by the International Association of Wood Anatomists (IAWA Committee
 1989) was followed. The photomicrographs of the sections were taken from
 the Carl Zeiss Compound light microscope (Scope.A1.Axio) equipped with
 Carl Zeiss camera. AxioVision Rel 4.0 software was used to capture the
 microscopic images. Ecological
 adaptability of a species described by measurement of mesomorphy (M) and
 vulnerability index (VI) were calculated by using the following formulas.
 Vulnerability and mesomorphy were calculated using vessel dimensions
 including mean vessel frequency. Since vessel frequency is not computed
 for ring porous species according to the terminology given by IAWA
 committee (1989) for hardwood identification, hence, only diffuse porous
 woods were considered here, excluding <i>Q. acutissima </i>and
 <i>Q. griffithii. </i> Mesomorphy (M) = Vulnerability x Mean vessel length <b>Cluster analysis</b> The average values of different quantitative wood anatomical characters of diffuse-porous oaks, including vessel length, vessel diameter, vessel frequency, inter-vessel pit size, fibre length, fibre diameter, fibre lumen diameter, fibre cell wall thickness, ray height, ray width, cell number and ray per mm (for uniseriate  rays) were subjected to Hierarchical cluster analysis using STATISTICA 7.0. The hierarchical grouping results in formation of a dendrogram which shows a relationship among species that are most similar.