UNIVERSITI PUTRA MALAYSIA

RADIAL VARIATION OF WOOD AXIAL ELEMENTS IN YOUNG ACACIA MANGIUM WILLD. AND SERIAL CROSS SECTIONING OF

SHOREA LEPROSULA MIQ.

KIYOKO HONJO

FH 2002 3

RADIAL VARIATION OF WOOD AXIAL ELEMENTS IN YOUNG ACACIA MANGIUM Willd. AND SERIAL CROSS SECTIONING OF

SHOREA LEPROSULA Miq.

BY

KIYOKO HONJO

Thesis Submitted to the School of Graduate Studies, Universiti Putra Malaysia, in Fulfillment of the Requirements for the Degree of Master of Science

Universiti Putra Malaysia

February 2002

Abstract of thesis presented to the Senate-of Universiti Putra Malaysia in fulfilment of the requirements for the degree of Master of Science

RADIAL VARIATION OF WOOD AXIAL ELEMENTS IN ACACIA MANGIUM Willd. AND SERIAL CROSS SECTIONING OF

SHOREA LEPROSULA Miq.

By

Kiyoko Honjo

February 2002

Chairman : Associate Professor Mohd. Hamami Sabri, Ph. D.

Faculty Forestry

Wood quality, namely wood structure, physical and mechanical

properties, and other qualities of woodworking, are greatly influenced by

the proportion, type, morphology, arrangement, distribution, and specific

gravity of xylem constituent cells. The present study was conducted to

determine the radial variation pattern of wood axial elements in Acacia

mangium Willd. In addition, the suitability of serial cross sectioning

technique for wood fibre length determination in Slwrea leprosula Miq. was

also investigated.

In the first part of the study, the radial variation pattern in the

length of wood fibre and vessel element in Acacia mangium was investigated

to reveal the difference in the pattern between dominant and suppressed

ii

trees. The correlation between the radial variation of wood fibre length and

monthly climatic factors (average temperature and precipitation) in the

early stage of tree growth was established.

Wood fibre length gradually increased from the pith to the bark

and leveled off at a distance of 3 to 4 em from the pith in dominant trees,

but increased throughout the stem in suppressed trees of about 4 em

diameter. Vessel element length remained at approximately 0.2 mm across

the stem, although the length tended to increase slightly outward.

The radial variation pattern of wood fibre length was related to the

radial tendency in the frequency of cell divisions in cambium rather than

the age of the tree. The results of the cross-correlation function between the

wood fibre increment and the climatic factors showed that its monthly

increment was correlated to monthly precipitation in a few previous

months rather than that in the same month. This suggests that the radial

growth in the tree was active prior to increase in rainfall.

Three-dimensional analysis of wood fibre morphology using serial

cross sectioning was conducted on Slwrea leprosula Miq., for detailed

analysis of the morphology without using special and expensive device.

iii

Serial cross sectioning provides precise information on the location and the

length of wood fibre in each radial file.

Comparing the wood fibre length measured using serial cross

sectioning and maceration, the result obtained by the former was

approximately 0.1 mm shorter than the latter. To obtain a serial cross

sectioning, more precise measurement of wood fibre length in an objective

lens of greater resolution power showed be used to detect the exact tip of

the fibre apex.

iv

Abstrak tesis yang dikemukakan kepada Senat Universiti Putra Malaysia sebagai memenuhi kepeduan untuk ijazah Master Sains.

VARIASI UNSUR MENEGAK PADA ARAH JEJARI DI DALAM KA YU MUD A Acacia mangium Willd. DAN SIRI HIRISAN PERMUKAAN

RENTAS ShoTea lepTosula Miq. SEEDLINGS

Oleh

Kiyoko Honjo

Februari 2002

Pengerusi : Profesor Madya Mohd. Hamami Sabri, Ph. D.

Fakulti : Perhutanan

Kualiti kayu khususnya stI"uktur kayu, sifat fizikal dan mekanikal

dan kualiti lain di dalam kerja kayu (woodworking) banyak dipengaruhi oleh

nisbah, jenis, morfologi, susunan, taburan dan ketumpatan bandingan sel

xylem. Tujuan kajian ini dijalankan adalah untuk menentukan corak

variasi arah jejari gentian kayu Acacia mangium Willd. dan Shorea leprosuJa

Miq. Selain dari itu , kesesuaian teknik siri hirisan permukaan rentas untuk

menentukan panjang gentian Shorea leprosula juga diselidik.

Dalam bahagian pertama kajian, perbezaan corak variasi arab jejari

panjang gentian dan panjang elemen vesel dian tara pokok Acacia mangium

Willd. yang dominan dan suppressed diselidik. Selain dari itu kaitan antara

v

eorak variasi jejari panjang gentian dengan faktor euaca bulanan (suhu dan

hujan) dalam peringkat permulaan pertumbuhan pokok juga dikaji.

Panjang gentian semakin meningkat dari empulur ke arah kulit kayu

dan sekata pada jarak 3 em hingga 4 em daripada empulur dalam pokok

dominan, manakala panjang gentian pada pokok suppressed meningkat

pada keseluruhan batang iaitu dari empulur hingga ke arah kulit kayu

pada jarak 4 em. Purata panjang vesel lebih kurang 0.2 mm dan tidak

berubah pada keseluruhan batang, walaupun panjangnya sedikit

meningkat ke arah kulit

Perbezaan bentuk panjang gentian kayu arab jejari adalah berkait

dengan kecenderungan arah jejari dalam kekerapan pembahagian sel

dalam kambium dan bukan umur pokok. Keputusan fungsi cross­

correlation antara pertambaban panjang gentian dan faktor cuaca

menunjukkan terdapat korelasi antara pertambahan panjang dengan

kelembapan bulanan pada beberapa bulan lepas dan tidak pada bulan yang

sarna. Kemungkinan pertumbuhan arab jejari pada batang pokok aktif

pada bulan yang banyak menerima hujan.

vi

Analisa 3-dimensi morfologi gentian kayu menggunakan siri hirisan

rentas kayu Sizorea leprosliia secara terperinci tanpa menggunakan perala tan

yang mahal. Siri hirisan rentas dapat menyediakan kedudukan tepat

gentian dan panjang gentian dapat ditentukan tanpa menggunakan analisa

statistik seperti yang perlu dilakukan jika menggunakan kaedah maserasi

(maceration) .

Perbandingan mengukur panjang gentian menggunakan kedua-dua

kaedah iaitu siri hirisan rentas dan maserasi mendapati dengan

menggunaan kaedah siri hirisan rentas panjang gentian adalah 0.1 rom

lebih pendek berbanding dengan kaedah maserasi. Untuk mendapatkan

ketepatan ukuran yang jitu siri hirisan permukaan rentas resolusi kanta

objektif yang tinggi mesti digunakan untuk mengesan kedudukan sebenar

kedua-dua hujung gentian.

vii

ACKNOWLEDGEMENTS

I would like to express my profound gratitude to Assoc. Prof. Dr.

Mohd. Hamami Sahri, the chairman of my supervisory committee, for his

guidance and suggestions throughout the course of my study and in

preparation of this thesis. My sincere appreciation is also extended to Dr.

Zaidon Ashaari and Dr. Wong Ee Ding, members of my advisory committee,

for their suggestions and comments.

My sincere appreciation goes to Prof. Dr. Fujita Minoru and Prof. Dr.

Nobuchi Tadashi of Kyoto University for their kind assistance, provision of

facilities, and invaluable suggestions, comments and encouragement I am

also thankful to Prof. Dr. Furukawa Ikuo of Tottori University for his

support and encouragement

Acknowledgements are also extended to Mr. Hasidin Abd. Rashid

and all the staff of the Faculty of Forestry, Universiti Putra Malaysia, who

have helped and provided me the facilities needed throughout the course of

my studies.

I would like to convey my deepest thanks to my dearest family

members, my father Papa san, mother Mama san and younger sister Satoko

viii

for their constant support and unfailing encouragement. Furthermore, I wish

to express my special thanks to my friends in Nepal, Phurba dai, Pasang dai,

Ang Dawa san, Dendi san, Ang Pasang san, Kitemba san and all friends of

Sherpa for giving me the strength and courage. Thank you very much to my

friends in UPM, and especially to my housemate Kak Azilah and Kak Lailan,

and my roommate Poppo for constant encouragement, and especially to

Ogata Yoshiyuki, thank you so much for your assistance, suggestions, and

guidance in my master's study, and to all of my dearest friends in Japan.

Finally, especially to Wong san, thank you so much for invaluable

suggestions, comments and constructive criticisms which led to the

completion of this thesis.

ix

I certify that an Examination Committee met on 4th February 2002 to conduct the final examination of Kiyoko Honjo on her Master of Science thesis entitled "Radial Variation of Wood Axial Elements in Young Acacia mangium Willd. and Serial Cross Sectioning of Silorea leprosula Miq." in accordance with Universiti Pertanian Malaysia (Higher Degree) Act 1980 and Universiti Pertanian Malaysia (Higher Degree) Regulations 1981. The Committee recommends that the candidate be awarded the relevant degree. Members of the Examination Committee are as follows:

MOHD. ZIN JUSOH Associate Professor/Lecturer, Faculty of Forestry, Universiti Putra Malaysia (Chairperson)

MOHD. HAMAMI SAHRI, Ph.D. Associate Professor/Lecturer, Faculty of Forestry, Universiti Putra Malaysia (Member)

WONG EE DING, Ph.D. Lecturer, Faculty of Forestry, Universiti Putra Malaysia (Member)

ZAIOON ASHAARI, Ph.D. Associate Professor/Lecturer, Faculty of Forestry, Universiti Putra Malaysia (Member)

AINI IDERIS, Ph.D. Professor, Dean, School of Graduate Studies, Universiti Putra Malaysia

Date:

x

This thesis submitted to the Senate of Universiti Putra Malaysia has been accepted as fulfilment of the requirement for the degree of Master of Science.

AINI IDERIS. Ph.D. Professor /Dean, School of Graduate Studies, Universiti Putra Malaysia

Date: 11 �PR 2002

xi

DECLARATION

I hereby declare that the thesis is based on my original work except for quotations and citations which have been duly acknowledged. I also declare that it has not been previously or concurrently submitted for any other degree at UPM or other institutions .

...... * .. t:E.t.1�.� ..................... . Kiyoko Honjo

Date: 2b! 2/2002

xii

TABLE OF CONTENTS

Pages

ABSTRACT ... ......... ... ....................................... ............ ............ ii

ABSTRAK........ ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ... . . . . . . ... . . . ... ... ... v

ACKNOWLEDGEMENTS .................. ... ...........• ......... ... ... .......... viii

APPROVAL ... ............ ... . . . ... ...... ............... ...... .. . ......... ......... ...... x

DECLARATION . . . . . . . . . ... ... . . . . . . . . . . . . ... . . . . . . ... ... . . . . . . . . . ... . . . ... ... ... ... ... xii

TABLE OF CONTENTS ............ .. . ... . . . . .. .. . ......... ......... ...... ...... ..... xiii

LIST OF TABLES... ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ... . . . . . . . . . ... . . . . . . . .. ... . . . . . . . xv

LIST OF FIGURES . . . ... . . . ... . . . . . . .. . "' . . ... . . . . . . ... ... . . . . . . ... ... ... . . . . . . . . . ....... xvi

LIST 0 F PLATES... ... ... . . . . . . ... . . . . . . . . . . . . . . . ... . . . ... . . . ... .. . .. . . . . ... ... ... ... xviii

CHAPTER

1 INTRODUCTION

1.1 Background . . . . . . . . . . .. . . . . . . . .. . . .. ... . . . . . . . . . .. . . .... .. . . . . . . . . . . 1

1.2 Justification. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

1.3 Objectives . . . ... . . .... . . . . .. . . .. . . .. . . . . . . ... . . . . . . . . . . . ... . . . . . ...... 5

2 LITERATURE REVIEW .................................................... 6

2.1 Xylem Constituent Elements ... . . . . .. . . . . .. . . . . . . . . . . .. . . .. . . . . . 6

2.1.1 Wood Fibre .. . .. . .. . . . . ... .. . . . .. . . . . . . . . . . . ... . . . . . . . . .... 7

2.1.2 Vessel Element . . . . .. . . . . . . . . . . ... . . . . .... . . . ... . .. .. . . . . . . 10

2.2 Characteristics of Variation in the Lengths of

Wood Fibre and Vessel Element .. .. . . .... . . . . . . ...... . . . . . ... .. . 12

2.2.1 Mature and Juvenile Wood . . . . ... .. . . . . . . . . . . .. . . . . . . 12

2.2.2 Radial Variation Patterns in the Lengths of Wood Fibre and Vessel Element.. . .... . .... . . ... ...... 14

2.2.3 Attempt of Setting the Boundary between

Mature and Juvenile Zones . . . . . . . .... .... . .. . . . . . . . . . 15

2.2.4 Location of Stable Point of Cell Length . . . ....... . .. 17

2.2.5 Factors Influencing the Cell Length and its

Variation Pattern . . . . ... .. . . . . . . . . . .. . ..... ... . .. . . ....... 19

2.2.6 Classification of the Variation Pattern in

Cell Length . . . .. . . . . . . . .. ... ..... . . . . . . . . . . . . . . . . .. . . . . .... 21

xiii

3 RADIAL VARIATION IN THE LENGTHS OF WOOD FIBRE

AND VESSEL ELEMENT IN YOUNG ACACIA MANGIUM

Willd ................ ..................... ... ............... ... ...... ...... ....... 26

3.1 Introduction ..... . ........ . ........ . ........ . ....... . ...... . ......... 26

3.2 Materials and Methods . .. .. . . .. ....... . . ........ . .. . ..... . ........ 28

3.2.1 Materials . . . . ..... . . . .. . ...... . . . .......... ........... . . .... 28

3.2.2 Methods .. . . .. . .... . .. . ...... ... ..... . .. .. . ..... . . . ......... 31

3.3 Results and Discussions ............... . ......... . . . . . . ............ 39

3.3.1 Effect of Tree Dominance on Radial Variation

Pattern of Cell Lengths .... . .. . ......... . ...... . ... . ... . . 39

3.3.2 Effect of Distance from the Pith on Radial

Variation Pattern of Wood Fibre Length ..... . ..... 45

3.3.3 Effects of Oimatic Factors on Radial Variation

of Cell Lengths ....... . ..... .... . . . . . ....... .. ..... ..... . .. 5 1

3.4 Conclusion . ......... . . . ... .... . . . . ....... . . . . . ........ ... . ... ........ 58

4 THREE-DIMENSIONAL ANALYSIS OF WOOD FIBRE

MORPHOLOGY USING SERIAL CROSS SECTIONS OF

SHOREA LEPROSULA. Miq ............. ....... . . ... ...... ... ............. 59

4.1 Introduction ...... . . . . . ......... . '" .............. ................... 59

4.2 Materials and Methods ..... . .. . . ....... . . . . .... . . ...... . .. . ...... 61

4.2.1 Materials . ... ... . . . . ... ... ..... ..... . .... .... ....... .. . . . ... 61

4.2.2 Methods ... .. ... ....... .. . . .. ...... ..... . .. . . . . . .. .. . . . . . .. 62

4.3 Results and Discussion . . .. ...... ....... . ....... ... ... . . ..... ... .. 71 4.3.1 Measurement of Wood Fibre Length Using

Serial Cross Sectioning Technique ....... .......... .. 71

4.3.2 Three-Dimensional Morphology of Wood

Fibres in S.leprosula .. . . . ... . .. . .. . . ... . .. . . .. . . . . . . .. . . 74

4.3.3 Comparison of the Lengths of Wood Fibre

Measured by Serial Cross Sectioning and

Maceration Methods ........ . .. .. . .................. . .... 77

4.4 Conclusion ...... ..... . ...... ... .. . ..... . .... . . ........ . ... .... .. . . ... 79

5 GENERAL CONCLUSION .••... •..... ... ....•.... ....•. •........... ....• 80

REFERENCES... ... ... .. . ... ... . .. ... ... ... ... ... ... ... ... ... . . . .. . .. . .. . ... .. . . .. . .. ... 82 APPENDICES ... ... ...... ... ............ ... ... ... ... ............ ... ... ... ............... 87 BIODAT A OF THE AUTHOR ............ ... .....• ...... .•....... ... ......... ....• 103

xiv

LIST OF TABLES

Table Page

2.1 Classification of fibre shapes in sample species .. . . . . . . . ..... . . . . . . . . . . . . . . . 8

2.2 Classification of radial variation types in sample species . . . '" .... " ... 23

3.1 Coding of the selected Acacia mangium WiUd. tree samples . . . . . . . . . .... 29

xv

LIST OF FIGURES

Figure Page

2.1 Classification of fibre cells......... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

2.2 Classification of radial variation patterns in the lengths of wood fibre and vessel element. ... . ................ . . .. . . ........ . . . .. . . ... . ... . . . . ... . . 22

3.1 Relationship between radial growth and girth at breast height (GBH) ........ .... . . ...... . . ..... . . ..... ....... .... ..... .... . . . . . . ..... . . . . . . . . ........ 32

3.2 Flowchart indicating the process of temporary slide preparation . .... 34

3.3a Radial variation patterns of the lengths of wood fibre and vessel element in 2-year-old A. mangium trees........................ 40

3.3b Radial variation patterns of the lengths of wood fibre and vessel element in 3-year-old A. mangium trees ........................ 41

3.4 Comparison of the radial variation pattern of the lengths of wood fibre and vessel element among 2-, 3- and 13-year-old A. mangium trees .... .... . . . . ....... . . .. ............. .. . .......... . .... . . . . . . . . . . . .. 42

3.5 Variation of wood fibre length with respect to the distance from the pith........................... . ..... . ... . .. . . ......... . . . ...... .... ........ 47

3.6 Variation of wood fibre length with relative distance from the pith .. . ... . . .... . . . ...... . . .. ...... . . ..... . ... . . . ....... . . . . . ..... ... .. ...... .... . . 48

3.7 Variation of wood fibre length versus time (month) ...................... 50

3.8 Flowchart indicating the process of cross-correlation function of wood fibre length increment in Am26...... .. .... ............ ... ..... . ... 52

3.9 Cross-correlogram between the fluctuation in wood fibre length increment and monthly precipitation......................................... 54

3.10 Cross-correlogram between the fluctuation in wood axial elements in Am27 and monthly average temperature................... 57

xvi

4.1 Experimental wood block . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ... .. . . .. 62

4.2 Measuring the Feret's diameter of wood fibre..... .... . . .. ... . . ... . . . ... . . . 68

4.3 Transformation of wood fibre image for fibre length measurement.. . . . . . . . .. .. . . . .. . ... .... . . . . ...... . . . ........... ..... ................ 70

4.4 An example of serial cross sections of S. leprosula and its corresponding data on wood fibre length... . . . . .. ............... ........... 73

4.5 Feret's radial and tangential diameters of wood fibre . . .. . . . . ..... . ...... 75

4.6 A comparison of wood fibre length of S. leprosula obtained using maceration and serial cross sectioning... .. . ........ .... .. . ... ..... . . 78

xvii

LIST OF PLATES

Plate Page

3.1 Experimental plot in Hutan Simpan Ayer Hitam, Puchong, Selangor, Peninsular Malaysia . . . .. . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . ..... ,. 28

3.2 Experimental disk of Am01 ...................................................... 30

3.3 Image analyzer . . . . . . . . . . . . . . . . . . . . . . . ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

3.4 Light microscope ................................................................... 36

4.1 Experimental disk of 4-year-old Slwrea leprosula tree . . . ......... . . . . . . . . . . 61

4.2 Cross sectional views near the apex and across the body of wood fibres . . . . . . .. . . .. . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . .. . . . . . . . . . . . . 65

4.3 Transformation of images for wood fibre dimension measurement using Photoshop and NIH Image software ............... 67

xviii

CHAYfER ONE

INTRODUCTION

1.1 Background

The term /I wood quality" refers to the texture, physical and

mechanical properties of wood which in turn affect its processing

properties. The indices which are frequently used for the measurement of

wood quality include wood fibre length, height and distribution of ray

tissue, and the proportion of vessel and ray tissue. The characteristics of

these elements vary considerably among species and trees, even at different

heights within a tree or across the trunk at the same height.

In addition to wood density which is generally recognised to be the

most important and efficient index for wood strength, wood properties are

greatly influenced by the proportion of certain types of xylem constituent

cells, their arrangement and distribution. The characteristics of hardwood

are basically dependent on the chemical and morphological properties of

the xylem constituent cells, i.e. wood fibres, which constitute up to 60 % of

the total volume of wood.

1

Wood fibre length, one of the most important morphological

factors, generally depends on the location of the fibre within a trunk. The

fibre length is usually the shortest at the pith, gradually increases outward,

and finally becomes constant at a certain point (known as 1/ stable point")

within the xylem. In most of the tropical trees, very little is known about

the radial and vertical variation patterns of wood fibres, hence the stable

point cannot be determined, although substantial work has been conducted

to determine the average length of wood fibres (Peh et aL 1986; Sahri et al.

1993; Urn and Gan 2000). In typical tropical trees, the variation pattern of

wood fibre length with time is not known, since these trees do not have

annual rings. It is therefore impossible to investigate the relationship

between its variation pattern and climatic factors.

This study is divided into two main parts. The first part reports the

radial variation pattern of the lengths of wood fibre and vessel element in

young Acacia mangium Willd. trees, a fast growing species, followed by the

establishment of correlation between the wood fibre length variation and

radial growth rate based on increment of girth at breast height

Subsequently, the effects of selected climatic factors on the radial variations

of fibre length, vessel element length, fibre increment and fibre elongation

ratio were also established.

2

In the second part, a serial cross section technique was introduced

to examine the wood fibre morphology in 4-year-old Shorea leprosula Miq., a

slow growing species. Different from the conventional maceration method,

this technique provides more precise information on the length of fibres

corresponding to their exact location in each radial section, instead of

relying on the current maceration method which only presents an

approximation based on statistical means. This technique was not adopted

for A. mangium sample trees as the xylem cells in these trees had undergone

a greater degree of elongation, and the cell arrangement was too

complicated for identification on the cross section.

3

1.2 Justification

Information on the radial variation of the length of wood fibre and

vessel element in A. mangium and S. leprosula, and their correlations with

the climatic factors over time, could provide a better understanding on the

growth behavior of these fast! slow growing hardwood species. These

fundamental data can be related to the wood properties, which can lead to

more efficient timber utilisation.

Successful application of the serial cross section technique in

hardwood species enables determination of wood fibre length at exact

location in the radial section, instead of relying on the current maceration

method which only presents an approximation based on statistical means.

4

1.3 Objectives

This study aims to

1. investigate the radial variation pattern of the lengths of wood fibre

and vessel element in Acacia mangium trees and determine the wood fibre

maturation point, i.e., the point at which the fibre length becomes constant.

2. compare the radial variation pattern of the lengths of wood fibre and

vessel element between dominant and suppressed Acacia mangium trees.

3. evaluate the relationship between the radial variation in the length of

wood fibres and monthly climatic factors (average temperature and

precipitation) in the early stage of tree growth in Acacia mangium.

4. attempt and evaluate the serial cross sectioning method for

measuring the dimension of wood fibre in Slwrea leprosula.

5

CHAPTER TWO

LITERATURE REVIEW

2.1 Xylem Constituent Elements

Xylem constituent elements of both coniferous and dicotyledonous

trees are contained almost exclusively within the secondary xylem. These

elements are derived by cambial division and composed of several types of

cells including conductive tissues.

The xylem in conifers is constituted of tracheid and parenchyma as

axial elements, with ray tracheid and ray parenchyma as radial elements. The

axial tracheids are particularly predominant, making up approximately 90%

of the total axial constituent elements (Appendix 1-1). Other elements, i.e.,

axial and ray parenchyma and intercellular canal, account for approximately

0.9,3.8 and 0.8%, respectively.

In general, broad-leaved trees evolved more than conifers and have

various cell types for specialized functions (Furuno and Watanabe 1994). The

main xylem constituents of hardwood are wood fibres, vessel elements,

tracheids, and parenchyma cells (axial elements), with ray parenchyma as

the predominant radial element (Appendices 1-2 and 1-3). In both Japanese

and tropical broad-leaved trees, the proportion of wood fibre is generally the

6