ANATOMICAL PROPERTIES OF AFINA [Strombosia glaucescensvar lucida (J. LEONARD)]

F.A. Awuku

Forestry Re~earch Institute of GhanaUST P.O. Box 63, Kumasi, Ghana

ABSTRACT - The study was carried out to det~i.~~inethe anatomical propertiesof Afina (Strombosia glaucescens) to assist~ the understanding of itsphysical and mechanical properties:

The results indicate that Afina is a diffuse-porous wood. The parenchymacells are apotracheal diffuse-in-aggregate. The rays are 2 to 3 cells wide.Afina has an average fibre length of 1.57mm with a Runkel Ratio of 7.54.The wood is har~, with fairly straight grain and the texture is fine. Thefibres are thick-walled.

Afina wood being hard, fairly straight grain and of fine texture may berecommended for uses such as tool handles.

Keywords - S~rombosia glaucescens, anatomical properties, fibre dimensions.

INTRODUCTION

There are about 680 species oftrees in the h~gh forests of Ghanaof which about 130 grow to timbersize. However only about 50species is of commercialimportance now. The remaining '.species are not utilizedsignificantly because some of themao not occur in commercial

quantities (TEDB unpubl. data).

The selection of any species ofwood for utilization is determined

by properties such as strength,durability, colour, density andfigure which are influenced by itsanatomical, chemical as well, asphysical characteristics. ,

In Ghana, Afina (Strombosiaglaucescens var. lucida (J.Leonard)] is found mostly in thewet and moist evergreen and themoist semi-deciduous formations.Afina is one of the lesser~used

species of which there is notenough information. It grows to aheight of about 30.5m and anaverage exploitable girth of1.22m. (Irvine 1961). The bolewhich is straight makes it a goodpromising t~mber tree, hence theneed to study its properties.

The purpose of this study was todetermine the anatomical

properties of the species with the

Gh-. Journal of Forestry Vol.1 1994

aim of determining some uses forwhich this species can be used.

MATERIALS AND METHODS

Five trees of Afina were randomlyselected and felled from theBobiri Forest Reserve,about 30kmsouth- east of Kumasi,in the moistsemi-deciduous forest.

Preparation Of Permanent SlidesFor Description •

A block of 10mm x 10mm x 40mm ofAfina wood (heartwood) taken fromeach of the five trees was boiled

in water for 48 hours prior tosectioning. Thin sections (15microns thickness) of cross,longitudinal radial, andlongitudinal tangential were cutwith a sliding microtome. The thinsections were then stained insafran in and mounted in CanadaBalsam for examination and

description.

Maceration And Fibre Measurements

To separate wood fibres formeasurements, match-stick size ofthe wood were put into test-tubescontaining equal volumes ofglacial

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Three dimensional microscopic septions of Afina (Strombosia glaucescens)

Fig.1a

Fig.1b

/i

Fig.1e

.• Gh_ Journalof Forestry Vol.1 1994 31

Table 1: Fibre diaensions of Afina (S~rombosia g1aucescens).

Parameters measured

Fibre length romFibre diameter ~m2 x wall-t,hickness (2w) ~mLumen width (1) ~mRunkel Ratio [2w]

L

Minimum

1.0019.7917.312.477.01

Maximum

2.5042.0537.104.947.51

Mean

1.5727.7024.193.317.31

Table 2: Fibre lengths of Afina and some tropical hardwood speciesfound to be suitable for production of paper.

Species

Strombosia glaucescens (Afina)

Terminalia ivorensis (Emire)

Musanga cercropioides (Odwuma)

Trip1ochiton scleroxylon (Wawa)

Pycnanthus angolensis (ofie)

Fibre length (mm)

1. 57

1.20

1.39

1.30

1.40

Source: Anatomy Section of the Forestry Research Institute ofGhana (Unpublished).

acetic acid and hydrogen peroxide(20 vol.), heated in a water-bathat a temperature of 60°C for 48hours. The resultant macerated

wood was then washed under tap~water, teased and mounted forfibre measurements.

The fibre lengths were determinedby projecting the fibres on ascreen and measuring whole fibreswith a paper rule specificallycalibrated for this purpose.Measurements were made of 50randomly selected fibres from eachof the five trees.

Diameter, wall-thickness and lumendiameter were measured on 30

randomly selected fibres with aneye-piece micrometer.

RESULTS

The wood is hard as tested withthumb nail. The sapwood isyellowish and the heartwood ispale brown in colour. The wood hasno characteristic taste or odour.

The grain is fairly straight andthe texture fine.

VesselsIn cross section the vessels are

Ghana Jour~L of Forestry VoL.1 1994

oval to circular in shape,moderately numerous and' inmultiples of 2 to 4. They arediffuse porous, and are radiallyarranged. Tyloses are present inthe vessels (Fig.la). Crystals ofrhomboidal shapes are present inthe vessels. The average diameterof vessels is 76.3~m (ranging from48.5 to 113.2~m). Perforationplates are scalariform.

Parenchyma

Parenchyma cells are abundant,apotracheal and diffuse-in­aggregate. Crystals of rhomboidalshape are present in theparenchyma cells (Fig.lb).

RaysThe rays are heterogeneous typeII, non-stored. The averagemaximum height is 576~m (range355.7 to 970.1~m) and the averagewidth is 32.01~m (range 24.3 ­48~m). The rays are commonly 2 to3 cells wide.

FibreThe fibres are libriform, aseptateand non-stored and overlap witheach other. The fibre dimensionsare shown in Table 1.

The average fibre length is 1.57mm

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makes it unsuitable for pulp andpaper production. Darkwa (1973)reports that thick-walled fibresrequire high beating for thefibres to develop the necessarystrength during the production ofpulp and'·paper. The thick fibresand high fibre lengths arecontributory factors for its highmechanical strength. However itsuse as structural timber is

affected by poor workingproperties due to high crystalcontent which blunts cuttingtools. Nevertheless, its fairlystraight grain and fine texturemakes it suitable for toolhandles.

DISCUSSION

with average wall thickness of24.19~m and Runkel Ratio of 7.31(Table 1).

Afina is a high density wood.Addae-Mensah et al (1989) reportedthe density to be 896 kgm3• Thehigh density~ay be attributed tothe thick-walled fibrescharacteristic of the wood.Compared to some well~knowntropical hardwoods suitable forpaper production Afina hasrelatively longer fibre length(Table 2). Although it has a highfibre length its high Runkel Ratio

ACKNOWLEDGEMENT - I am grateful to Messrs F.W. Addo-Ashong of Efficonsult,F.K.K. Ampong, of FORIG, and Dr J. Ocloo of BRRI for their invaluablesuggestions, criticisms and guidance. My special appreciation also goes toMiss. Ruth Esi Awunyo and Mr. Bukari Dramani of FORIG Anatomy section forthe preparation of thin wood sections.

REFERENCES

Addae-Mensah, A.; Ayarkwa, J;Mohammed A.I.; & Azerengo, E.(1989). Users' guide of someGhanaian Secondary and Primarytimber species based on strengthand related properties. ForestProducts Research InstituteInformation Bulletin No.9.

Darkwa, N.A. (1973). Problems ofutilizing tropical mixed hardwoodsin the production of pulp andpaper. FPRI Tech. Newsl. 7(1 & 2}p.19.

Irvine, F.R. (1961). Woody plantsof Ghana. Oxford University Press,London, p.472-473.

GhanaJournal of Forestry Vol.1 1994 33